Publikationen - Strukturanalytik
Jahr ab 2022
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Triangular-shaped Cu–Zn–In–Se-based nanocrystals with narrow near infrared photoluminescence
Bora, A.; Fu, N.; Saha, A.; Prudnikau, A.; Hübner, R.; Bahmani Jalali, H.; Di Stasio, F.; Gaponik, N.; Lesnyak, V.
Abstract
Tunable optical properties exhibited by semiconductor nanocrystals (NCs) in the near infrared (NIR) spectral region are of particular interest in various applications, such as telecommunications, bioimaging, photodetection, photovoltaics, etc. While lead and mercury chalcogenide NCs do exhibit exemplary optical properties in the NIR, Cu–In–Se (CISe)-based NCs are a suitable environment-friendly alternative to these toxic materials. Several reports of NIR-emitting (quasi)spherical CISe NCs have been published, but their more complex-shaped counterparts remain rather less explored. The emerging anisotropic nanomaterials have gained significant interest owing to their unique optical properties arising due to their specific shape. While several examples of non-spherical Cu–In–S-based NCs have been reported, examples of CISe-based anisotropic NCs are rather scarce, and those with intensive photoluminescence (PL) are not yet developed. In this work, we present a one-pot approach to synthesize quaternary Cu–Zn–In–Se (CZISe) triangular NCs with intensive PL in the NIR region. The NCs synthesized exhibit tetragonal crystal structure and, depending on the reaction conditions, are single triangular particles or stacks of triangular blocks of varied lateral sizes but rather uniform thickness. The synthesis involves the formation of In2Se3 seeds with subsequent incorporation of copper and growth of triangular CISe NCs, followed by the incorporation of zinc and the growth of a ZnS shell. Importantly, the PL band widths of the final core/shell heterostructured NCs are narrow, down to 102 meV, which is a rarely observed characteristic for this class of materials and can be attributed to their anisotropic shape and the absence of thickness and compositional inhomogeneities of their building blocks. The PL of the CZISe/ZnS NCs can be tuned in the range of 1082-1218 nm reaching a quantum yield of up to 40% by varying their size and composition. To the best of our knowledge, this is the farthest and the narrowest PL achieved for CISe-based NCs so far, which widens application perspectives of this material in NIR LEDs, bioimaging, and photovoltaics.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 40937) publication
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Nanoscale 17(2025), 2577-2588
DOI: 10.1039/d4nr04499a
Permalink: https://www.hzdr.de/publications/Publ-40937
Combining Liposomal Photocatalysts with Whole-Cell Catalysts for One-pot Photobiocatalysis
Zhang, J.; Batista, V. F.; Hübner, R.; Vogel, S.; Wu, C.
Abstract
Cooperative photobiocatalytic processes have seen extensive potentials for the synthesis of both bulk and fine chemicals owing to their versatility, eco-friendliness, and cost-effectiveness. Nevertheless, developing a universal and effective synthetic strategy compatible with both catalytic systems remains challenging. In this study, we explored cationic liposomes as biocompatible photocatalyst encapsulation systems and combined them with bacteria overexpressing enzymes for two-step and three-step cascade reactions. Specifically, the water-soluble photocatalyst anthraquinone-2-sulfonate (AQS), which can oxidize benzyl alcohol, is encapsulated within the core of cationic liposomes composed of dioleoyl-3-trimethylammonium propane (DOTAP) and the helper lipid cholesterol. The positive charge on the liposome surface enabled electrostatic interactions with the negative charges on the membrane of Escherichia coli cells. Bacterial cells overexpressing various enzymes, such as Candida antarctica lipase B (CalB) and benzaldehyde lyase (BAL), and coated with liposomes enabled the production of added value compounds through cascade reactions with excellent production. These cascades involve CalB-catalyzed hydrolysis, BAL-catalyzed condensation, and AQS-driven photo-oxidation reactions. Therefore, the strategy offers more possibilities of combining photocatalysis with biocatalysis for recoverability, enhanced mass transfer, and enhanced compatibility in both industrial biotechnology and synthetic chemistry.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 40892) publication
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Small 21(2025), 2408666
DOI: 10.1002/smll.202408666
Permalink: https://www.hzdr.de/publications/Publ-40892
A Supramolecular Approach to Engineering Living Cells with Enzymes for Adaptive and Recyclable Cascade Synthesis
Wang, S.; Hübner, R.; Karring, H.; Batista, V. F.; Wu, C.
Abstract
Biocatalytic transformation in nature is inherently dynamic, spontaneous, and adaptive, enabling complex chemical synthesis and metabolism. These processes often involve supramolecular recognition among cells, enzymes, and biomacromolecules, far surpassing the capabilities of isolated cells and enzymes used in industrial synthesis. Inspired by nature, here we design a supramolecular approach to equip living cells with these capacities, enabling recyclable, efficient cascade reactions. Our two-step “plug-and-play” methodology begins by coating Escherichia coli cells with guestcontaining polymers (SupraBAC) via supramolecular charge interactions, followed by the introduction of β-cyclodextrin-functionalized host enzymes through host-guest chemistry, creating a robust cell-enzyme complex. This supramolecular coating not only protects cells from various stresses, such as UV radiation, heat, and organic solvents, but also facilitates the overexpression of intracellular enzymes and the attachment of extracellular enzymes within and on SupraBAC. This combination results in efficient multienzyme cascade synthesis, enabling two- and three-step reactions in one pot. Importantly, the multienzyme system can be recycled up to five times without significant loss of activity. Our findings introduce a versatile, adaptive supramolecular coating for whole-cell catalysts, offering a sustainable and efficient solution for complex synthesis in both chemistry and industrial biotechnology.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 40844) publication
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Angewandte Chemie - International Edition 64(2025), e202416556
Online First (2024) DOI: 10.1002/anie.202416556
Permalink: https://www.hzdr.de/publications/Publ-40844
Manipulating multimetallic effects: Programming size-tailored metal aerogels as self-standing electrocatalysts
Cui, Q.; Li, Y.; Sun, X.; Weng, B.; Hübner, R.; Cui, Y.; Zhang, Q.; Luo, Y.; Zhang, L.; Du, R.
Abstract
Metal aerogels are emerging porous materials composed entirely of nanostructured metals, which manifest broad prospects in diverse fields. Particularly, multimetallic aerogels (MMAs) receive increasing attention due to their widely tunable properties stimulated by the synergy of multiple metals. However, the investigation of multimetallic effects in MMAs is predominantly restricted to optimizing their application performances. Here, the untrivial multimetallic effects on the synthetic aspect are discovered, and the underlying mechanisms are unveiled, offering new perspectives for manipulating the sol-gel process and tuning the ligament size (dL) of MMAs by designing the average bulk density (rhoab) and atomic radius (ra) mismatch. Moreover, a sedimentation-based non-destructive method is established, which solves the long-lasting challenge of preparing intact metal-gel-based electrocatalysts and yields record-high performances toward alcohol oxidation reactions.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 40707) publication
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Matter 8(2025), 101905
Online First (2024) DOI: 10.1016/j.matt.2024.10.023
Permalink: https://www.hzdr.de/publications/Publ-40707
Design of Metal Aerogels-Based 3D SERS Substrates by Gentle Compression
Zhou, L.; Liu, Y.; Li, Y.; Long, C.; Zhou, S.; Hübner, R.; Li, Y.; Xue, G.; Lin, D.; Xu, W.; Hu, Y.; Du, R.
Abstract
Metal aerogels (MAs) are emerging all-nanometal-structured self-standing porous materials featuring exceptional performances in diverse fields. They have recently been adopted as 3D surface-enhanced Raman scattering (SERS) substrates, while the less utilization of the unique porous structure leads to limited performance. Here, a fascinating compression-mediated regulation strategy is presented to largely boost the SERS performance of Au-Ag aerogels. By gently pressing, both the density of hot spots and the inter-ligament distance can be efficiently modulated, thus enabling to flexibly manipulate the SERS properties of MAs. On this basis, a record-high misfocus tolerance (∼8.8 mm), low detection limit (down to 0.1 nM), high stability (>1 month), reusability, and multiplex detection ability are concurrently realized. This study may point out a new direction for engineering 3D SERS substrates with tunable and exceptional performance.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 40374) publication
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Advanced Functional Materials 35(2025), 2412006
Online First (2024) DOI: 10.1002/adfm.202412006
Permalink: https://www.hzdr.de/publications/Publ-40374
Engineering living cells with polymers for recyclable photoenzymatic catalysis
Ning, J.; Sun, Z.; Hübner, R.; Karring, H.; Ebbesen, M. F.; Dimde, M.; Wu, C.
Abstract
Engineering cell membranes for catalysis is challenging due to their inherent complexity. Here we introduce a polymeric strategy to overcome these challenges by chemically modifying cell membranes with catalytic polymers, enabling robust, recyclable and photoenzymatic catalysis. Through a one-step in situ atom transfer radical polymerization on living Escherichia coli cells, polymers are generated to protect the cells from environmental stressors while facilitating chemoenzymatic synthesis by integrating catalytic polymers with intracellular enzymes. As a proof of concept, a photoenzymatic cascade with an anthraquinone-based polymer and benzaldehyde lyase is demonstrated, converting benzyl alcohol into benzoin and achieving bioconversion yields that are 15 times higher than controls. Additionally, cells serve as large biological scaffolds for polymers, enabling recycling of macromolecular catalysts. A recyclable chemoenzymatic system incorporating an organometallic polymer with intracellular enzymes is also presented. Our versatile, straightforward approach offers a technology platform for engineering cell membranes for cascade synthesis, with broad implications for synthetic chemistry, polymer chemistry and biotechnology.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 40303) publication
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Nature Catalysis 7(2024), 1404-1416
DOI: 10.1038/s41929-024-01259-5
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-40303
Artificial metalloenzymes enabled by combining proteins with hemin via protein refolding
Ouyang, J.; Zhang, Z.; Hübner, R.; Karring, H.; Wu, C.
Abstract
In this study, we unveil a conceptual technology for fabricating artificial metalloenzymes (ArMs) by deeply integrating hemin into protein scaffolds via a protein refolding process, a method that transcends the conventional scope of surface-level modifications. Our approach involves denaturing proteins, such as benzaldehyde lyase, green fluorescent protein, and Candida antarctica lipase B, to expose extensive reactive amino acid residues, which are then intricately linked with hemin using orthogonal click reactions, followed by protein refolding. This process not only retains the proteins’ structural integrity but expands proteins’ functionality. The most notable outcome of this methodology is the hemin@BAL variant, which demonstrated a remarkable 83.7% conversion rate in cyclopropanation reactions, far surpassing the capabilities of traditional hemin-based catalysis in water. This success highlights the significant role of protein structure in the ArMs’ activity and marks a substantial leap forward in chemical modification of proteins. Our findings suggest vast potentials of protein refolding approaches for ArMs across various catalytic applications, paving the way for future advancements in synthetic biology and synthetic chemistry.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 40112) publication
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Chinese Journal of Catalysis 67(2024), 157-165
DOI: 10.1016/S1872-2067(24)60150-6
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-40112
Structural Regulation of Au-Pt Bimetallic Aerogels for Catalyzing the Glucose Cascade Reaction
Wang, C.; Wang, L.; Nallathambi, V.; Liu, Y.; Kresse, J.; Hübner, R.; Reichenberger, S.; Gault, B.; Zhan, J.; Eychmüller, A.; Cai, B.
Abstract
Bimetallic nanostructures are promising candidates for the development of enzyme-mimics, yet the deciphering of the structural impact on their catalytic properties poses significant challenges. By leveraging the structural versatility of nanocrystal aerogels, this study reports a precise control of Au-Pt bimetallic structures in three representative structural configurations, including segregated, alloy, and core-shell structures. Benefiting from a synergistic effect, these bimetallic aerogels demonstrate improved peroxidase- and glucose oxidase-like catalytic performances compared to their monometallic counterparts, unleashing tremendous potential in catalyzing the glucose cascade reaction. Notably, the segregated Au-Pt aerogel shows optimal catalytic activity, which is 2.80 and 3.35 times higher than that of the alloy and core-shell variants, respectively. This enhanced activity is attributed to the high-density Au-Pt interface boundaries within the segregated structure, which foster greater substrate affinity and superior catalytic efficiency. This work not only sheds light on the structure-property relationship of bimetallic catalysts but also broadens the application scope of aerogels in biosensing and biological detections.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39744) publication
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Advanced Materials 36(2024), 2405200
DOI: 10.1002/adma.202405200
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-39744
Transition from ferromagnetic to noncollinear to paramagnetic state with increasing Ru concentration in FeRu films
Lisik, J.; Rojas, M.; Myrtle, S.; Ryan, D. H.; Hübner, R.; Omelchenko, P.; Abert, C.; Ducevic, A.; Suess, D.; Soldatov, I.; Schaefer, R.; Seyd, J.; Albrecht, M.; Girt, E.
Abstract
The structural and magnetic properties of sputter-deposited Fe100−xRux films were studied for x < 50. The crystal structure of Fe100−xRux is shown to be predominantly body-centered cubic for x < 13 and to undergo a gradual transition to hexagonal close-packed in the Ru concentration range 13 < x < 20. Magnetic measurements indicate that the addition of Ru to Fe gives rise to a noncollinear magnetic alignment between Fe atoms in the body-centered cubic FeRu alloys, while the hexagonal close-packed FeRu alloys exhibit paramagnetic behavior. A simple atomistic model was used to show that the competition between ferromagnetic coupling of neighboring Fe atoms and antiferromagnetic coupling of Fe atoms across Ru atoms in cubic FeRu structures can induce noncollinear magnetic order. Magnetic multilayer structures used in thin-film magnetic devices make extensive use of both Fe and Ru layers. Our results reveal that the presence of even a small amount of Ru in Fe influences the magnetic order of Fe, which could impact the performance of these devices.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39679) publication
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Physical Review B 110(2024), 104429
DOI: 10.1103/PhysRevB.110.104429
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Permalink: https://www.hzdr.de/publications/Publ-39679
Antiferromagnetic nanoscale bit arrays of magnetoelectric Cr2O3 thin films
Rickhaus, P.; Pylypovskyi, O.; Seniutinas, G.; Borras, V.; Lehmann, P.; Wagner, K.; Zaper, L.; Prusik, P.; Makushko, P.; Veremchuk, I.; Kosub, T.; Hübner, R.; Sheka, D. D.; Maletinsky, P.; Makarov, D.
Abstract
Magnetism of oxide antiferromagnets (AFMs) has been studied in single crystals and extended thin films. The properties of AFM nanostructures still remain underexplored. Here, we report on the fabrication and magnetic imaging of granular 100-nm-thick magnetoelectric \ch{Cr2O3} films patterned in circular bits with diameters ranging from 500 down to 100\,nm. With the change of the lateral size, the domain structure evolves from a multidomain state for larger bits to a single domain state for the smallest bits. Based on spin-lattice simulations, we show that the physics of the domain pattern formation in granular AFM bits is primarily determined by the energy dissipation upon cooling, which results in motion and expelling of AFM domain walls of the bit. Our results provide a way towards the fabrication of single domain AFM-bit-patterned memory devices and the exploration of the interplay between AFM nanostructures and their geometric shape.
Keywords: Cr2O3; bit memory
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Nano Letters 24(2024)42, 13172-13178
DOI: 10.1021/acs.nanolett.4c03044
Permalink: https://www.hzdr.de/publications/Publ-39649
Role of competing magnetic anisotropies in deriving topologically nontrivial spin textures in oxide heterostructures
Sahoo, J.; Vagadia, M.; Hübner, R.; Bhatt, N.; Kumar, A.; Sahastrabuddhe, G.; Janay Choudhary, R.; Shankar Singh, R.; Rana, D. S.
Abstract
In spatially inverted systems, the complex entanglement of Dzyaloshinskii-Moriya interaction (DMI) and other magnetic anisotropies, mediated by spin-orbit coupling (SOC), influences the emergence and dynamics of the chiral spin textures such as skyrmion. The competing and unified effect of these anisotropies - which is expected to amplify the skyrmionics response in the quantum transport phenomena - is not yet known. Here, we investigate this template and engineer the topological Hall effect (THE) arising from chiral spin texture in a range of La0.7Sr0.3MnO3/CaIrO3 superlattices. The strength of SOC and interfacial DMI are controlled via the architectural design and charge transfer across the interface. All the superlattices display anomalous Hall effect, accompanied by the hump like feature. In (L3Iy)4 (y = 4, 6, and 8) superlattices, the humplike feature that is deemed as the THE is intrinsic in nature and stems from the chiral spin texture. For the intermediate strength of SOC, unique eightfold anisotropic magnetoresistance oscillations manifest owing to the modulation of the magnetic easy axis in the presence of competing anisotropies. For this superlattice, THE shows remarkable enhancement of the order such that it takes complete precedence over anomalous contribution. The thicker superlattice with higher fraction of charge transfer augments ferromagnetic interactions, and the artificial THE appears as a consequence of a dual-channel anomalous Hall effect. This manipulation of the THE is intricately connected to the concurrent presence of magnetic anisotropies, altering the dynamics of chiral spin texture. These findings expand the understanding of the corroborative contributions of competing anisotropies and yield a comprehensive control of chiral properties - a dimension for the utility in next-generation spintronics technologies.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39630) publication
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Physical Review B 110(2024), 104422
DOI: 10.1103/PhysRevB.110.104422
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-39630
Self-healing ThSiO4-ZrSiO4 system under conditions relevant to underground nuclear waste repositories
Svitlyk, V.; Weiß, S.; Garbarino, G.; Shams Aldin Azzam, S.; Hübner, R.; Worbs, A.; Huittinen, N. M.; Hennig, C.
Abstract
Two series of Th1-xZrxSiO4 phases were synthesized hydrothermally under weakly basic (pH = 8) and strongly acidic (pH = 1) conditions. Changes in pH were found to have a significant effect on experimental phase diagrams. Synthesis at pH = 8 favors the formation of Th-rich phases with resulting Th1-xZrxSiO4 solid solution for x = 0 – 0.5. Contrary, synthesis at pH = 1 results in the formation of pure end-members of the ThSiO4-ZrSiO4 pseudo-binary system separated by multiple miscibility gaps. Phases formed both under basic and acidic conditions were found to retain water, which can be discharged from the structure upon heating. A different high-pressure (HP) behaviour was found for Th-rich and Zr-rich solid solutions. While Th-rich Th0.9Zr0.1SiO4 and Th0.6Zr0.4SiO4 phases retain their stoichiometry and crystal structure upon compression at HP, a significant reduction of the Th occupancy related to a decrease of the Th-O distances is observed for the Th-poor Th0.26Zr0.74SiO4 phase at P > 8 GPa, with the subsequent formation of a Th-rich amorphous phase. The Th diffusion between the crystalline and amorphous phases was found to be fully reversible. This unique self-healing property makes these phases promising candidates for nuclear applications under extreme pressure and temperature conditions, in particular those found in underground repositories.
Beteiligte Forschungsanlagen
- Rossendorf Beamline an der ESRF DOI: 10.1107/S1600577520014265
Verknüpfte Publikationen
- DOI: 10.1107/S1600577520014265 is cited by this (Id 39571) publication
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Acta Materialia 281(2024), 120357
DOI: 10.1016/j.actamat.2024.120357
Permalink: https://www.hzdr.de/publications/Publ-39571
Direct Synthesis of Pd2+-Rich Palladene Aerogels as Bifunctional Electrocatalysts for Formic Acid Oxidation Reaction and Oxygen Reduction Reaction
Wang, C.; Wei, W.; Georgi, M.; Hübner, R.; Steinbach, C.; Bräuniger, Y.; Schwarz, S.; Kaskel, S.; Eychmüller, A.
Abstract
In this work, we developed a direct strategy to fabricate Palladene (i. e. Palladium metallene) aerogels and propose a temperature-dependent growth mechanism. Besides the typical three-dimensional networks and wrinkled surface morphologies, the as-prepared Palladene50 aerogel is endowed with abundant Pd2+. The as-prepared Palladene50 aerogel exhibits an excellent mass activity in the formic acid oxidation reaction and a good half-wave potential in the oxygen reduction reaction in comparison with Pd/C and a Pd aerogel. This work expands the range of metal aerogels from the perspective of the building block units and demonstrates a direct approach to fabricate highly promising bifunctional electrocatalysts for fuel cells.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39540) publication
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ChemElectroChem 11(2024), e202400060
DOI: 10.1002/celc.202400060
Cited 3 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-39540
The effect of Ar+ and N+ ion irradiation on the thermally induced evolution of the structural and magnetic properties of Co/Pt and Pt/Co bilayered stacks
Pedan, R.; Kruhlov, I.; Makushko, P.; Dubikovskyi, O.; Kosulya, O.; Orlov, A.; Bodnaruk, A.; Golub, V.; Munnik, F.; Hübner, R.; Makarov, D.; Vladymyrskyi, I.
Abstract
The application of Co-Pt thin films as functional elements of novel nanoelectronics and spintronics devices requires the formation of a homogeneous ferromagnetic CoPt phase with tunable magnetic properties. A diffusion-controlled synthesis of this ferromagnetic phase can be implemented through the annealing of deposited Co/Pt bilayers. Apart from thermal treatment, both structural and magnetic properties of such layered stacks can be affected by ion preirradiation. In this work, we, therefore, studied the effect of a two-stage process consisting of preirradiation with 110 keV Ar+/N+ ions followed by post-annealing in vacuum at 550 °С for 30 min on the evolution of the structural, chemical, and magnetic properties of Co/Pt/substrate and Pt/Co/substrate heterostructures. The results obtained for such two-stage processing were compared to those received after single-stage vacuum annealing. It was found that when ion preirradiation is followed by annealing, the diffusion-driven intermixing of Pt and Co leading to the formation of the ferromagnetic Co-Pt phase is slowed down compared to the non-irradiated samples, which is associated with the barrier effect of implanted projectiles. Furthermore, we demonstrate that preirradiation does not compromise the magnetic properties of the samples. For instance, preirradiation leads to a coercivity increase of up to 38% compared to the non-irradiated annealed samples which is attributed to the presence of remaining paramagnetic Pt between the grains of the ferromagnetic A1-CoPt phase. We demonstrate that the applied two-stage processing (consisting of ion preirradiation followed by thermal annealing) of magnetic thin films is a promising approach for tailoring their magnetic properties such as the in-plane coercivity, saturation, and effective magnetization.
Keywords: magnetic thin films; ion irradiation; diffusion; Co-Pt alloy; crystal structure
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39460) publication
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Materials Chemistry and Physics 327(2024), 129862
DOI: 10.1016/j.matchemphys.2024.129862
Permalink: https://www.hzdr.de/publications/Publ-39460
Spin Effect to Regulate the Electronic Structure of Ir-Fe Aerogels for Efficient Acidic Water Oxidation
Gao, C.; Wang, J.; Hübner, R.; Zhan, J.; Zhao, M.; Li, Y.; Cai, B.
Abstract
"Spin" has been recently reported as an important degree of electronic freedom to promote catalysis, yet how it influences electronic structure remains unexplored. This work reports the spin-induced orbital hybridization in Ir-Fe bimetallic aerogels, where the electronic structure of Ir sites is effectively regulated by tuning the spin property of Fe atoms. The spin-optimized electronic structure boosts oxygen evolution reaction (OER) electrocatalysis in acidic media, resulting in a largely improved catalytic performance with an overpotential of as low as 236 mV at 10 mA cm-2. Furthermore, the gelation kinetics for the aerogel synthesis is improved by an order of magnitude based on the introduction of a magnetic field. Density functional theory calculation reveals that the increased magnetic moment of Fe (3d orbital) changes the d-band structure (i.e., the d-band center and bandwidth) of Ir (5d orbital) via orbital hybridization, resulting in optimized binding of reaction intermediates. This strategy builds the bridge between the electron spin theory with the d-band theory and provides a new way for the design of high-performance electrocatalysts by using spin-induced orbital interaction.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39438) publication
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Small 20(2024), 2400875
DOI: 10.1002/smll.202400875
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-39438
Optical Thin Films in Space Environment: Investigation of Proton Irradiation Damage
Corso, A. J.; Padovani, M.; Santi, G.; Hübner, R.; Kentsch, U.; Bazzan, M.; Pelizzo, M. G.
Abstract
The present work reports a systematic study of the potential degradation of metals and dielectric thin films in different space environments. The mono- and bilayers selected are made of materials commonly used for the realization of optical components, such as reflective mirrors or building blocks of interferential filters. More than 400 samples were fabricated and irradiated with protons at different energies on ground-based facilities. The fluences were selected as a result of simulations of the doses delivered within a long-term space mission considering different orbits (Sun close, Jovian, and Geostationary orbits). In order to stress the samples at different depths and layer interfaces, experiments were carried out with a range of proton energies within 1 and 10 MeV values. An estimate of a safe maximum fluence has been provided for each type of sample at each energy. The damage mechanism, when present, has been investigated with different optical and structural techniques.
Keywords: coatings; metals; dielectrics; proton irradiation; space environment; optical instruments; telescope
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39379) publication
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ACS Applied Materials and Interfaces 16(2024), 38645-38657
DOI: 10.1021/acsami.4c03362
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-39379
Influence of interface morphology on the magnetic damping of Al-sandwiched Permalloy thin films
Ney, V.; Lenz, K.; Ganss, F.; Hübner, R.; Lindner, J.; Ney, A.
Abstract
The magnetic damping of Ni80Fe20 (Permalloy, Py) thin films is studied via frequency-dependent ferromagnetic resonance (FMR) experiments. The thickness of the Py films is kept constant and they are all protected from oxidation by an identical 5-nm-thick Al cap layer. To separate the Py film from the oxidic sapphire substrates a systematic variation of the thickness of an additional Al spacer layer was carried out. Py sandwiched in Al exhibits a low, purely Gilbert-like magnetic damping when the Al spacer layer thickness is kept below 3 nm. Above this thickness the magnetic damping is strongly increased due to a pronounced two-magnon contribution. A detailed investigation of the temperature dependence as well as full angular dependence of the FMR allows for correlating the magnetic properties of the Py with the microscopic structural properties of the films as studied by x-ray reflectivity and transmission electron microscopy. It turns out that the detrimental twomagnon processes are activated by an island-like growth of the Al spacer layers, which leads to rough, wavy interfaces with characteristic length scales of the order of ten nanometers. Nevertheless, for Al spacer layers with a thickness below 3 nm a low, purely Gilbert-like magnetic damping can be observed.
Keywords: ferromagnetic resonance; linewidth; damping; interfaces; roughness; magnetization dynamics; permalloy
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39375) publication
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Data publication: Influence of oxidic and metallic interfaces on the magnetic …
ROBIS: 37643 HZDR-primary research data are used by this (Id 39375) publication
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Physical Review Materials 8(2024), 114410
DOI: 10.1103/PhysRevMaterials.8.114410
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Permalink: https://www.hzdr.de/publications/Publ-39375
Multi-Level Switching of Spin-Torque Ferromagnetic Resonance in 2D Magnetite
Jia, Z.; Chen, Q.; Wang, W.; Sun, R.; Li, Z.; Hübner, R.; Zhou, S.; Cai, M.; Lv, W.; Yu, Z.; Zhang, F.; Zhao, M.; Tian, S.; Liu, L.; Zeng, Z.; Jiang, Y.; Wang, Z.
Abstract
2D magnetic materials hold substantial promise in information storage and neuromorphic device applications. However, achieving a 2D material with high Curie temperature (TC), environmental stability, and multi-level magnetic states remains a challenge. This is particularly relevant for spintronic devices, which require multi-level resistance states to enhance memory density and fulfil low power consumption and multi-functionality. Here, the synthesis of 2D non-layered triangular and hexagonal magnetite (Fe3O4) nanosheets are proposed with high TC and environmental stability, and demonstrate that the ultrathin triangular nanosheets show broad antiphase boundaries (bAPBs) and sharp antiphase boundaries (sAPBs), which induce multiple spin precession modes and multi-level resistance. Conversely, the hexagonal nanosheets display slip bands with sAPBs associated with pinning effects, resulting in magnetic-field-driven spin texture reversal reminiscent of “0” and “1” switching signals. In support of the micromagnetic simulation, direct explanation is offer to the variation in multi-level resistance under a microwave field, which is ascribed to the multi-spin texture magnetization structure and the randomly distributed APBs within the material. These novel 2D magnetite nanosheets with unique spin textures and spin dynamics provide an exciting platform for constructing real multi-level storage devices catering to emerging information storage and neuromorphic computing requirements.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39302) publication
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Advanced Science 11(2024), 2401944
DOI: 10.1002/advs.202401944
Cited 2 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-39302
Enhanced Near-Infrared Absorption in Au-Hyperdoped Si: Interplay Between Mid-Gap States and Plasmon Resonance
Peng, S.; Wang, T.; Shaikh, M. S.; Hübner, R.; Tian, M.; Huang, Y.; Heller, R.; Zhu, J.; Su, Y.; Li, Y.; Xie, Z.; Li, L.; Zhou, S.; Wang, M.
Abstract
Detecting near-infrared (NIR) light with high efficiency is crucial for photodetectors that are applied in optical communication systems. Si hyperdoped with deep-level impurities provides a monolithic platform for infrared optoelectronics with room-temperature operation at telecommunication wavelengths. In this work, we present strongly enhanced NIR absorption via the hybridization between plasmon resonance and mid-gap states in Au-hyperdoped Si layers, prepared by ion implantation and pulsed laser melting. The Au-hyperdoped Si layers exhibit high-quality recrystallization with the substitution of Au atoms into the Si matrix and the formation of Au nanoclusters on the surface. Surprisingly, the Au-hyperdoped Si layers exhibit a NIR absorption with spectral response extending up to 1650 nm and maximum absorptance up to 30%. According to the electromagnetic simulation, the enhanced infrared photoresponse can be attributed to the mid-gap states induced by substitutional Au atoms and the localized surface plasmon resonance associated with the Au nanoclusters. This work presents a simplified one-step process to gain significant enhancement of NIR absorption, which paves a way for the realization of Si-based photodetectors with room-temperature operation and outstanding performance.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39294) publication
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Optics Express 32(2024), 32966-32976
DOI: 10.1364/OE.532127
Permalink: https://www.hzdr.de/publications/Publ-39294
Uranium (VI) reduction by an iron-reducing Desulfitobacterium species as single cells and in artificial multispecies bio-aggregates
Hilpmann, S.; Jeschke, I.; Hübner, R.; Deev, D.; Zugan, M.; Rijavec, T.; Lapanje, A.; Schymura, S.; Cherkouk, A.
Abstract
Microbial U(VI) reduction plays a major role in new bioremediation strategies for radi-onuclide-contaminated environments and can potentially affect the safe disposal of high-level radioactive waste in a deep geological repository. During the process, water-soluble and mobile U(VI) is converted into less-soluble, rather immobile U(IV). This reduction in solubility facilitates a separation of U from contaminated solutions in case of bioremediation efforts and prevents U contaminations of the groundwater in case of final repositories. Desulfitobacterium sp. G1-2, an iron-reducing bacterium, isolated from a bentonite sample, was used to investigate its potential to reduce U(VI) in differ-ent background electrolytes: bicarbonate buffer, where a uranyl(VI)-carbonate com-plex predominates, and synthetic Opalinus Clay pore water, where a uranyl(VI)-lactate complex plays the major role, as confirmed by time-resolved laser-induced fluores-cence spectroscopic measurements. While Desulfitobacterium sp. G1-2 rapidly removed almost all U from the supernatants in bicarbonate buffer, only a low amount of U was removed in Opalinus Clay pore water. UV/Vis measurements suggest a speciation-dependent reduction by the microorganism. Scanning transmission electron microsco-py coupled with energy-dispersive X-ray spectroscopy revealed the formation of two different U-containing nanoparticles inside the cells. In a subsequent step, artificial mul-tispecies bio-aggregates were formed using derivatized polyelectrolytes with cells of Desulfitobacterium sp. G1-2 and Cobetia marina DSM 50416 to assess their potential for U(VI) reduction under aerobic and anaerobic conditions. These findings provide new perspectives on U(VI) reduction by iron-reducing bacteria and contribute to the development of a comprehensive safety concept for high-level radioactive waste repos-itories, as well as to new bioremediation strategies.
Keywords: Microbial uranium(VI) reduction; Iron-reducing bacteria; Speciation-dependent reduction; Artificial biofilms
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Data publication: Uranium (VI) reduction by an iron-reducing …
ROBIS: 39285 HZDR-primary research data are used by this (Id 39282) publication -
Data publication: Uranium (VI) reduction by an iron-reducing …
RODARE: 3038 HZDR-primary research data are used by this (Id 39282) publication
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Science of the Total Environment 955(2024), 177210
DOI: 10.1016/j.scitotenv.2024.177210
Permalink: https://www.hzdr.de/publications/Publ-39282
At the limit of interfacial sharpness in nanowire axial heterostructures
Hilliard, D.; Tauchnitz, T.; Hübner, R.; Vasileiadis, I.; Gkotinakos, A.; Dimitrakopulos, G. P.; Komninou, P.; Sun, X.; Winnerl, S.; Schneider, H.; Helm, M.; Dimakis, E.
Abstract
As semiconductor devices approach dimensions at the atomic scale, controlling the compositional grading across hetero-interfaces becomes paramount. Particularly in nanowire axial heterostructures, which are promising for a broad spectrum of nanotechnology applications, the achievement of sharp hetero-interfaces has been challenging owing to peculiarities of the commonly used vapor-liquid-solid growth mode. Here, the grading of Al across GaAs/AlxGa1-xAs/GaAs heterostructures in self-catalyzed nanowires is studied, aiming at finding the limits of the interfacial sharpness for this technologically versatile material system. A pulsed growth mode ensures precise control of the growth mechanisms even at low temperatures, while a semi-empirical thermodynamic model is derived to fit the experimental Al-content profiles and quantitatively describe the dependences of the interfacial sharpness on the growth temperature, the nanowire radius, and the Al content. Finally, symmetrical Al profiles with interfacial widths of 2–3 atomic planes, at the limit of the measurement accuracy, are obtained, outperforming even equivalent thin-film heterostructures. The proposed method paves the way to advanced heterostructure schemes and a better exploitation of the nanowire platform; moreover, it is also considered expandable to other material systems and nanostructure types.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39217) publication
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ACS Nano 18(2024)32, 21171-21183
DOI: 10.1021/acsnano.4c04172
Permalink: https://www.hzdr.de/publications/Publ-39217
Si1-x-yGeySnx alloy formation by Sn ion implantation and flash lamp annealing
Steuer, O.; Michailow, M.; Hübner, R.; Pyszniak, K.; Turek, M.; Kentsch, U.; Ganss, F.; Khan, M. M.; Rebohle, L.; Zhou, S.; Knoch, J.; Helm, M.; Cuniberti, G.; Georgiev, Y.; Prucnal, S.
Abstract
For many years, Si1-yGey alloys have been applied in the semiconductor industry due to the ability to adjust the performance of Si-based nanoelectronic devices. Following this alloying approach of group-IV semiconductors, adding tin into the alloy appears as the obvious next step, which leads to additional possibilities for tailoring the material properties. Adding Sn enables effective band gap and strain engineering and can improve the carrier mobilities, which makes Si1-x-yGeySnx alloys promising candidates for future opto- and nanoelectronics applications. The bottom-up approach for epitaxial growth of Si1-x-yGeySnx, e.g., by chemical vapor deposition and molecular beam epitaxy, allows tuning the material properties in the growth direction only; the realization of local material modifications to generate lateral heterostructures with a such a bottom up approach is extremely elaborate since it would require the use of lithography, etching and either selective epitaxy or epitaxy and chemical-mechanical polishing giving rise to interface issues, non-planar substrates etc. This article shows the possibility of fabricating Si1-x-yGeySnx alloys by Sn implantation into Si1-yGey layers followed by millisecond-range flash lamp annealing. The materials are investigated by Rutherford backscattering spectrometry, micro Raman spectroscopy, X-ray diffraction, and transmission electron microscopy. The fabrication approach was adapted to ultra-thin Si1-yGey layers on silicon-on-insulator substrates. Finally, we show the possibility of implanting Sn locally in ultra-thin Si1-yGey films. We demonstrate the realization of vertical AND lateral Si1-x-yGeySnx heterostructures by tin ion implantation and flash lamp annealing.
Keywords: Implantation; SiGeSn; Si1-x-yGeySnx; Sn; FLA; Flash lamp annealing
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39097) publication
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Si1-x-yGeySnx alloy formation by Sn ion implantation and flash lamp annealing
ROBIS: 39199 HZDR-primary research data are used by this (Id 39097) publication
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Journal of Applied Physics 136(2024)6, 065701
DOI: 10.1063/5.0220639 -
Poster
EMRS Fall Meeting 2024, 16.-19.09.2024, Warsaw, Poland
Permalink: https://www.hzdr.de/publications/Publ-39097
Formation and specific contact resistivity of NiGe on polycrystalline Ge made by flash lamp annealing
Begeza, V.; Rebohle, L.; Stöcker, H.; Mehner, E.; Hübner, R.; Zhou, S.
Abstract
Flash lamp annealing (FLA) is an ultra-short annealing method, which excellently meets the requirements of thinfilm processing and microelectronics. Due to the relatively high hole mobility, thin Ge layers are highly interesting as a transistor channel material or generally as a functional layer in CMOS technology and for low-cost electronics. One possibility to realize ohmic contacts with low contact resistance is the use of metal germanides, especially the stoichiometric NiGe phase. In this work, NiGe contacts on thin Ge films were fabricated by magnetron sputtering followed by FLA. The evolution of microstructure was traced by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Electrical measurements focused on the determination of contact resistance by the circular transfer length method. The contacts were fabricated by two different approaches, and the influence of different process steps on the layer morphology and uncertainty of the measurement was studied. Finally, we show that FLA as a thermal treatment with a low thermal budget is able to form NiGe on p-type Ge with a low contact resistance similar to that achieved by other thermal treatments.
Keywords: Germanium; Nickel germanide; Thin films; Sputtering; Flash lamp annealing; Circular transfer length method
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 39029) publication
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Journal of Alloys and Compounds 990(2024), 174420
DOI: 10.1016/j.jallcom.2024.174420
Permalink: https://www.hzdr.de/publications/Publ-39029
Separated electronic and strain interfaces in core/dual-shell nanowires: unlocking the potential of strained GaAs for applications across near-infrared
Sun, X.; Pashkin, O.; Moebus, F.; Hübner, R.; Winnerl, S.; Helm, M.; Dimakis, E.
Abstract
Semiconductor nanowires have inspired plenty of novel nanotechnology device concepts in photonics, electronics, and sensing, owing to their unique functionalities and integrability in heterogeneous platforms. Lattice-mismatched core/shell heterostructures, in particular, open new avenues for strain engineering and material properties modification. A notable case is the widely tunable tensile strain in the core of GaAs/InxAl1-xAs core/shell nanowires, which can be used to tailor the GaAs bandgap for applications across near-infrared, like optical fiber telecommunication, imaging, photovoltaics, etc. As we show here, though, the bandgap narrowing under high tensile strain in the GaAs core is accompanied by a fast non-radiative recombination, which is undesirable for any device application. We reveal the limiting role of the lattice-mismatched core/shell interface and propose, instead, a novel core/dual-shell heterostructure that employs an intermediate AlyGa1-yAs shell (spacer). This spacer decouples the GaAs/AlyGa1-yAs interface, which confines electrons and holes into GaAs, from the lattice-mismatched AlyGa1-yAs/InxAl1-xAs one, whereas the strain in GaAs is unaffected. Choosing the optimal spacer thickness, the photoluminescence yield increases significantly, with longer emission decay lifetimes and slower carrier cooling rates. Besides unlocking the potential of GaAs for photonic applications across near-infrared, our proposed heterostructure concept could also be adopted for other material systems.
Keywords: nanotechnology; semiconductors; strain engineering; heterostructures; charge carrier dynamics
Verknüpfte Publikationen
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Data publication: Separated electronic and strain interfaces in …
ROBIS: 38930 HZDR-primary research data are used by this (Id 38909) publication
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Advanced Functional Materials 34(2024)30, 2400883
DOI: 10.1002/adfm.202400883
Permalink: https://www.hzdr.de/publications/Publ-38909
Structural changes in Ge1 xSnx and Si1-x-yGexSny thin films on SOI substrates treated by pulse laser annealing
Steuer, O.; Schwarz, D.; Oehme, M.; Bärwolf, F.; Cheng, Y.; Ganss, F.; Hübner, R.; Heller, R.; Zhou, S.; Helm, M.; Cuniberti, G.; Georgiev, Y.; Prucnal, S.
Abstract
Ge1 xSnx and Si1-x-yGexSny alloys are promising materials for future opto- and nanoelectronics applications. These alloys enable effective band-gap engineering, broad adjustability of their lattice parameter, exhibit much higher carrier mobility than pure Si, and are compatible with the CMOS technology. Unfortunately, the equilibrium solid solubility of Sn in Si1-xGex is less than 1% and the pseudomorphic growth of Si1-x-yGexSny on Ge or Si can cause in-plane compressive strain in the grown layer, degrading the superior properties of these alloys. Therefore, post-growth strain engineering by ultrafast non-equilibrium thermal treatments like pulse laser annealing (PLA) is needed to improve the layer quality. In this article, Ge0.94Sn0.06 and Si0.14Ge0.8Sn0.06 thin films grown on silicon-on-insulator substrates by molecular beam epitaxy were post growth thermally treated by PLA. The material is analyzed before and after the thermal treatments by transmission electron microscopy, X-ray diffraction (XRD), Rutherford backscattering spectrometry, secondary ion mass spectrometry, and Hall effect measurements. It is shown that after annealing, the material is single-crystalline with much better crystallinity than the as-grown layer. This is reflected in a significantly increased XRD reflection intensity, well-ordered atomic pillars, and increased active carrier concentrations up to 4ᵡ1019 cm-3.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38902) publication
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Data publication: Structural changes in Ge1 xSnx and Si1-x-yGexSny thin films …
ROBIS: 38905 HZDR-primary research data are used by this (Id 38902) publication
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Journal of Applied Physics 136(2024)5, 055303
DOI: 10.1063/5.0218703
Permalink: https://www.hzdr.de/publications/Publ-38902
Cobalt-based Co3Mo3N/Co4N/Co Metallic Heterostructure as a Highly Active Electrocatalyst for Alkaline Overall Water Splitting
Liu, Y.; Wang, L.; Hübner, R.; Kresse, J.; Zhang, X.; Deconinick, M.; Vaynzof, Y.; Weidinger, I. M.; Eychmüller, A.
Abstract
Alkaline water electrolysis holds promise for large-scale hydrogen production, yet it encounters challenges like high voltage and limited stability at higher current densities, primarily due to inefficient electron transport kinetics. Herein, a novel cobalt-based metallic heterostructure (Co3Mo3N/Co4N/Co) is designed for excellent water electrolysis. In operando Raman experiments reveal that the formation of the Co3Mo3N/Co4N heterointerface boosts the free water adsorption and dissociation, increasing the available protons for subsequent hydrogen production. Furthermore, the altered electronic structure of the Co3Mo3N/Co4N heterointerface optimizes ΔGH of the nitrogen atoms at the interface. This synergistic effect between interfacial nitrogen atoms and metal phase cobalt creates highly efficient active sites for the hydrogen evolution reaction (HER), thereby enhancing the overall HER performance. Additionally, the heterostructure exhibits a rapid OH- adsorption rate, coupled with great adsorption strength, leading to improved oxygen evolution reaction (OER) performance. Crucially, the metallic heterojunction accelerates electron transport, expediting the afore-mentioned reaction steps and enhancing water splitting efficiency. The Co3Mo3N/Co4N/Co electrocatalyst in the water electrolyzer delivers excellent performance, with a low 1.58 V cell voltage at 10 mAcm-2, and maintains 100% retention over 100 hours at 200 mAcm-2, surpassing the Pt/C // RuO2 electrolyzer.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38895) publication
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Angewandte Chemie - International Edition 63(2024), e202319239
DOI: 10.1002/anie.202319239
Cited 28 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-38895
Synthesis and Twin Polymerization of Si(OCH2py)4 for Nitrogen-containing Carbon Materials
Scharf, S.; Notz, S.; Pfefferkorn, K.; Rüffer, T.; Formánek, P.; Hübner, R.; Selyshchev, O.; Madeira, T. I.; Zahn, D. R. T.; Lang, H.
Abstract
The synthesis and twin polymerization (TP) of Si(OCH2py)4 (3a, py=2-cC5H4N; 3b, py=3-cC5H4N; 3c, py=4-cC5H4N) is discussed. The solid state structures of 3b, c were confirmed by single-crystal X-ray crystallography showing non-conventional H-bonding, forming 2D chains (3b) or 3D networks (3c). Thermally induced TP of 3a–c and their simultaneous polymerization with 2,2‘-spiro-bi[4H-1,3,2-benzodioxasiline] (4) is described. The resulting hybrid materials were characterized by 1H, 13C{1H}, and 29Si{1H} CP MAS NMR spectroscopy confirming the transformation of the SiOCH2 moieties into CH2 groups enabling the formation of the respective polymers. These results were supported by HAADF-STEM studies, displaying micro-structuring. Nitrogen-containing porous carbon materials C_1–C_3 show surface areas of 1300 and 1700 m2g-1, large pore volumes between 0.6–1.2 cm3g-1, and nitrogen contents of up to 3.1 at-%. X-ray photoemission spectroscopy reveal that pyrrolic, pyridine, and pyridone nitrogen atoms are present. If equimolar amounts of 3a–c and 4 are simultaneously polymerized in the presence of [Pd(OAc)2] (5), then the Pd nanoparticle-decorated material Pd@C_3 (900 m2g-1) was obtained, which showed k values of -0.083 and -0.066 min-1 in the reduction of methylene blue and methyl orange, proving the accessibility of the Pd NPs.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38798) publication
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European Journal of Inorganic Chemistry 27(2024), e202300656
DOI: 10.1002/ejic.202300656
Permalink: https://www.hzdr.de/publications/Publ-38798
Investigating the interaction of uranium(VI) with diatoms and their bacterial community: A microscopic and spectroscopic study
He, Y.; Wei, T.-S.; Kluge, S.; Flemming, K.; Sushko, V.; Hübner, R.; Steudtner, R.; Raff, J.; Mallet, C.; Beauger, A.; Breton, V.; Péron, O.; Stumpf, T.; Sachs, S.; Montavon, G.
Abstract
Diatoms and bacteria play a vital role in investigating the ecological effects of heavy metals in the environment. Despite separate studies on metal interactions with diatoms and bacteria, there is a significant gap in research regarding heavy metal interactions within a diatom-bacterium system, which closely mirrors natural conditions. In this study, we aim to address this gap by examining the interaction of uranium(VI) (U(VI)) with Achnanthidium saprophilum freshwater diatoms and their natural bacterial community, primarily consisting of four successfully isolated bacterial strains (Acidovorax facilis, Agrobacterium fabrum, Brevundimonas mediterranea, and Pseudomonas peli) from the diatom culture. Uranium (U) bio-association experiments were performed both on the xenic A. saprophilum culture and on the four bacterial isolates. Scanning electron microscopy and transmission electron microscopy coupled with spectrum imaging analysis based on energy-dispersive X-ray spectroscopy revealed a clear co-localization of U and phosphorus both on the surface and inside A. saprophilum diatoms and the associated bacterial cells. Time-resolved laser-induced fluorescence spectroscopy with parallel factor analysis identified similar U(VI) binding motifs both on A. saprophilum diatoms and the four bacterial isolates. This is the first work providing valuable microscopic and spectroscopic data on U localization and speciation within a diatom-bacterium system, demonstrating the contribution of the co-occurring bacteria to the overall interaction with U, a factor non-negligible for future modeling and assessment of radiological effects on living microorganisms.
Keywords: Achnanthidium saprophilum; 16S rRNA genes; Extracellular polymeric substance (EPS); Co-localization; Luminescence spectroscopy; Radionuclides; Uranium
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Ecotoxicology and Environmental Safety 284(2024), 116893
DOI: 10.1016/j.ecoenv.2024.116893
Permalink: https://www.hzdr.de/publications/Publ-38772
Phase composition and stability of Gd2-xThxZrO7 under extreme conditions
Svitlyk, V.; Weiß, S.; Gabarono, G.; Hübner, R.; Worbs, A.; Huittinen, N. M.; Hennig, C.
Abstract
Introduction of Th into a hydrothermally synthesized disordered fluorite-type Gd2Zr2O7 phase induces a transition to an ordered pyrochlore-type phase at a Th concentration of 10% at the Gd site (Gd1.8Th0.2ZrO7 composition). Degree of order of the fluorite-type phase reaches 50% for a Th concentration of 25% (Gd1.5Th0.5ZrO7 composition). Upon application of high pressure, the Gd2Zr2O7 phase retains fluorite-type structure until the pressure of 33 GPa (K0 = 167(1) GPa) where it undergoes a reversible amorphisation. The Gd1.7Th0.3ZrO7 phase was found to be stable until at least the pressure of 25 GPa (K0 = 169(3) GPa). Upon heating to Tmax of 1135 K, the Gd2Zr2O7 phase retains disordered fluorite-type structural arrangement (α = 3.03·10-5 K-1). Excellent stability of the Gd2-xThxZrO7 phases under extreme conditions of temperature and pressure makes Gd2Zr2O7 a promising candidate as a host matrix for radioactive species for safe long-term underground storage of nuclear waste.
Beteiligte Forschungsanlagen
- Rossendorf Beamline an der ESRF DOI: 10.1107/S1600577520014265
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- DOI: 10.1107/S1600577520014265 is cited by this (Id 38754) publication
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Zeitschrift für Kristallographie 239(2024)5-6, 199-205
DOI: 10.1515/zkri-2024-0066
Permalink: https://www.hzdr.de/publications/Publ-38754
Al-delta-doped ZnO films made by atomic layer deposition and flash-lamp annealing for low-emissivity coating
Zhang, G.; Steuer, O.; Li, R.; Cheng, Y.; Hübner, R.; Helm, M.; Zhou, S.; Liu, Y.; Prucnal, S.
Abstract
In this work, we have investigated and optimized the Al-delta-doped ZnO (δ -AZO) superlattices for mid-infrared applications. Thin films of δ -AZO are fabricated by atomic layer deposition (ALD) followed by millisecond-range (ms-range) flash-lamp annealing (FLA). During the FLA process, the superlattice structure is preserved and Al is electrically activated. The highest carrier concentration and lowest resistivity estimated from Hall-effect measurements are 2.7 × 1021 cm−3 and 8.8 × 10-4 Ωcm, respectively, for the δ -AZO superlattice with an Al:Zn ratio of 1:20. Moreover, glass substrates coated with the developed δ -AZO superlattice show a reflectance above 60 % in the near- and mid-infrared spectral range, while the transmittance in the visible range maintains above 80 %. The presented δ -AZO superlattice is a good alternative material to replace indium tin oxide films for cost-efficient low-emissivity glazing.
Keywords: Al-doped ZnO; Delta-doping; Flash-lamp Annealing; Low-Emissivity coating
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38568) publication
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Al-delta-doped ZnO films for low emissivity coating
ROBIS: 40322 is new version of this (Id 38568) publication
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Applied Surface Science 648(2024), 159046
Online First (2023) DOI: 10.1016/j.apsusc.2023.159046
Cited 7 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-38568
Intrinsic magnetic properties of the layered antiferromagnet CrSBr
Long, F.; Mosina, K.; Hübner, R.; Sofer, Z.; Klein, J.; Prucnal, S.; Helm, M.; Dirnberger, F.; Zhou, S.
Abstract
van der Waals magnetic materials are an ideal platform to study low-dimensional magnetism. Opposed to other members of this family, the magnetic semiconductor CrSBr is highly resistant to degradation in air, which, in addition to its exceptional optical, electronic, and magnetic properties, is the reason the compound is receiving considerable attention at the moment. For many years, its magnetic phase diagram seemed to be well-understood. Recently, however, several groups observed a magnetic transition in magnetometry measurements at temperatures of around 40 K that is not expected from theoretical considerations, causing a debate about the intrinsic magnetic properties of the material. In this Letter, we report the absence of this particular transition in magnetization measurements conducted on high-quality CrSBr crystals, attesting to the extrinsic nature of the low-temperature magnetic phase observed in other works. Our magnetometry results obtained from large bulk crystals are in very good agreement with the magnetic phase diagram of CrSBr previously predicted by the mean-field theory; A-type antiferromagnetic order is the only phase observed below the Néel temperature at TN = 131 K. Moreover, numerical fits based on the Curie–Weiss law confirm that strong ferromagnetic correlations are present within individual layers even at temperatures much larger than TN.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38205) publication
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Applied Physics Letters 122(2023), 222401
DOI: 10.1063/5.0175185
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-38205
Annealing-induced evolution of boron-doped polycrystalline diamond
Zhang, G.; Zulkharnay, R.; Ganss, F.; Guo, Y.; Alkhalifah, M.; Yang, L.; Zhang, S.; Zhou, S.; Li, P.; Li, Y.; Moshchalkov, V. V.; Zhu, J.; May, P. W.
Abstract
Diamond shows great promise for opening up new paradigms in the semiconductor industry and quantum electronics. Here, we investigate the influence of thermal annealing on the structural and electrical transport properties of heavily boron-doped polycrystalline diamond (BPD) thin films. Our structural analyses show that annealing beyond 600 °C can induce severe local amorphization in a BPD thin film and transform it into a binary mixture of spatially separate domains of amorphous carbon (a-C) and diamond grains. Due to this annealing-induced morphology and phase segregation, the BPD thin films demonstrate a significant decrease of the electron localization radius and a distinct increase of the Ginzburg-Landau coherence length. Our research provides physical insight into the conversion of diamond to a-C and aids in defining the application scope of BPD by revealing its heat tolerance.
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Physical Review Materials 8(2024)4, 044802
DOI: 10.1103/PhysRevMaterials.8.044802
Cited 1 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-38139
Recyclable pickering emulsions for enzymatic phenol degradation of oily wastewater
Gong, Z.; Gao, S.; Lu, K.; Hübner, R.; Wu, C.
Abstract
Enzymatic degradation offers a sustainable solution for waterborne phenolic pollutants. However, its application within industrial, non-aqueous contexts — particularly in mitigating phenolic contaminants in oily wastewater — remains significantly challenging. To address this challenge, the present study exploits the potential of Fe3O4@PDA nanoparticles to form oil-in-water Pickering emulsions for the enzymatic degradation process. The uniform stability of the prepared emulsion, with droplet sizes under 5 μm, protects enzyme activity and expands the water-oil interfacial area, leading to an enhancement in the efficiency of horseradish peroxidase (HRP) catalytic degradation. The application of this emulsion resulted in a substantial increase in the degradation rate of phenol, achieving 100% within 30 min as opposed to an only 13.6% without it. The study also highlights the excellent stability, reusability, and versatility of the Fe3O4@PDA nanoparticles, enabled by magnetic separation and their ability to form emulsions with diverse oil phases. Consequently, our research offers valuable insights into the development of environmentally sustainable strategies for the degradation of phenolic contaminants in various industrial oily wastewater.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38080) publication
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Colloids and Surfaces A: Physicochemical and Engineering Aspects 682(2024), 132922
Online First (2023) DOI: 10.1016/j.colsurfa.2023.132922
Cited 2 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-38080
Die Morphologie der Schuppen der aus der Paläarktis bekannten Arten der Unterfamilie Procridinae Boisduval, 1828 (Lepidoptera, Zygaenidae) und deren Bedeutung für die Systematik und Phylogenie
Keil, T.; Hübner, R.; Worbs, A.
Abstract
In dieser Arbeit werden erstmals die Form und Gestaltung der Schuppen der meisten (>90 %) der aus der Paläarktis bekannten Arten der Unterfamilie Procridinae Boisduval, 1828 abgebildet und Möglichkeiten der Determinationsunterstützung sowie deren Bedeutung für phylogenetische Interpretationen in Verbindung mit anderen morphologischen Merkmalen diskutiert.
The morphology of the scales of the Palaearctic species of the subfamily Procridinae Boisduval, 1828 (Lepidoptera, Zygaenidae) and their importance for systematics and phylogeny. – The present publication illustrates morphology and design of the scales of most (>90 %) of the Palaearctic species of the subfamily Procridinae Boisduval, 1828 for the first time. Possible support of identifications and the importance for phylogenetic interpretations in combination with other morphological features are discussed.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38079) publication
- Entomologische Nachrichten und Berichte 67(2023)3, 181-201
Permalink: https://www.hzdr.de/publications/Publ-38079
Synthesis and characterization of titanium and aluminum complexes of 2-methoxybenzyl alcoholate and their use in base-catalyzed twin polymerization
Scharf, S.; Rüffer, T.; Formánek, P.; Hübner, R.; Weber, M.; Mehring, M.; Lang, H.
Abstract
The synthesis and characterization of twin monomers [Ti(OCH2-2-MeO-C6H4)4(HOCH2-2-MeO-C6H4)]2 (3) and [Al(OCH2-2-MeO-C6H4)3]4 (5) by reacting HOCH2-2-MeO-C6H4 (1) with Ti(OiPr)4 (2), or 1 with AlMe3 (4) is discussed. Single crystal X-ray structure analysis of 3 shows a dimeric structure with two alkoxide ligands bridging the titanium ions, while the others are terminal bonded. The respective phenolic resin / metal oxide hybrid materials HM_Ti and HM_Al were obtained in moderate (HM_Ti) to excellent (HM_Al) yields using typical base-catalyzed twin polymerization conditions (230 °C, 2 h). Nuclear magnetic resonance and infrared spectroscopy as well as scanning electron microscopy and scanning transmission electron microscopy combined with energ-dispersive X-ray spectroscopy proved the formation of inorganic–organic hybrid materials consisting of resin and MxOy materials (HM_Ti, TiO2; HM_Al, Al2O3) containing interpenetrating phase nano-domains with sizes of < 5 nm, as is charcteristic for twin polymerization processes. Oxidation of HM_Ti and HM_Al yielded the respective oxide materials Ox_Ti (TiO2) and Ox_Al (Al2O3), which possess low surface areas of ABET = 53 m2/g and 76 m2/g, respectively.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38078) publication
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Inorganica Chimica Acta 561(2024), 121873
Online First (2023) DOI: 10.1016/j.ica.2023.121873
Permalink: https://www.hzdr.de/publications/Publ-38078
Complete Glucose Electrooxidation Enabled by Coordinatively Unsaturated Copper Sites in Metal-Organic Frameworks
Shi, X.; Ling, Y.; Li, Y.; Li, G.; Li, J.; Wang, L.; Min, F.; Hübner, R.; Yuan, S.; Zhan, J.; Cai, B.
Abstract
The electrocatalytic oxidation of glucose plays a vital role in biomass conversion, renewable energy, and biosensors, but significant challenges remain to achieve high selectivity and high activity simultaneously. In this study, we present a novel approach for achieving complete glucose electrooxidation utilizing Cu-based metal-hydroxide-organic framework (Cu-MHOF) featuring coordinatively unsaturated Cu active sites. In contrast to traditional Cu(OH)2 catalysts, the Cu-MHOF exhibits a remarkable 40-fold increase in electrocatalytic activity for glucose oxidation, enabling exclusive oxidation of glucose into formate and carbonate as the final products. The critical role of open metal sites in enhancing the adsorption affinity of glucose and key intermediates was confirmed by control experiments and density functional theory simulations. Subsequently, a miniaturized nonenzymatic glucose sensor was developed showing superior performance with a high sensitivity of 214.7 μAmM-1cm-2, a wide detection range from 0.1 μM to 22 mM, and a low detection limit of 0.086 μM. Our work provides a novel molecule-level strategy for designing catalytically active sites and could inspire the development of novel metal-organic framework for next-generation electrochemical devices.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38077) publication
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Angewandte Chemie - International Edition 62(2023), e202316257
DOI: 10.1002/anie.202316257
Cited 21 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-38077
Evolution of point defects in pulsed-laser-melted Ge1-xSnx probed by positron annihilation lifetime spectroscopy
Steuer, O.; Liedke, M. O.; Butterling, M.; Schwarz, D.; Schulze, J.; Li, Z.; Wagner, A.; Fischer, I. A.; Hübner, R.; Zhou, S.; Helm, M.; Cuniberti, G.; Georgiev, Y.; Prucnal, S.
Abstract
Direct-band-gap Germanium-Tin alloys (Ge1-xSnx) with high carrier mobilities are promising materials for nano- and optoelectronics. The concentration of open volume defects in the alloy, such as Sn and Ge vacancies, influences the final device performance. In this article, we present an evaluation of the point defects in molecular-beam-epitaxy grown Ge1-xSnx films treated by post-growth nanosecond-range pulsed laser melting (PLM). Doppler broadening – variable energy positron annihilation spectroscopy and variable energy positron annihilation lifetime spectroscopy are used to investigate the defect nanostructure in the Ge1-xSnx films exposed to increasing laser energy density. The experimental results, supported with ATomic SUPerposition calculations, evidence that after PLM, the average size of the open volume defects increases, which represents a raise in concentration of vacancy agglomerations, but the overall defect density is reduced as a function of the PLM fluence. At the same time, the positron annihilation spectroscopy analysis provides information about dislocations and Ge vacancies decorated by Sn atoms. Moreover, it is shown that the PLM reduces the strain in the layer, while dislocations are responsible for trapping of Sn and formation of small Sn-rich-clusters.
Beteiligte Forschungsanlagen
- Strahlungsquelle ELBE DOI: 10.17815/jlsrf-2-58
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
- P-ELBE
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 38017) publication
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 38017) publication
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Evolution of point defects in pulsed-laser-melted Ge1-xSnx probed by positron …
ROBIS: 37862 HZDR-primary research data are used by this (Id 38017) publication
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Journal of Physics: Condensed Matter 36(2024), 085701
Online First (2023) DOI: 10.1088/1361-648X/ad0a10
Cited 3 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-38017
Efficient Near-Infrared Light-Emitting Diodes Based on CdHgSe Nanoplatelets
Prudnikau, A.; Roshan, H.; Paulus, F.; Martín-García, B.; Hübner, R.; Bahmani Jalali, H.; de Franco, M.; Prato, M.; Di Stasio, F.; Lesnyak, V.
Abstract
Cadmium mercury selenide (CdHgSe) nanocrystals exhibit a unique combination of low-energy optical absorption and emission, which can be tuned from the visible to the infrared range through both quantum confinement and adjustment of their composition. Owing to this advantage, such nanocrystals have been studied as a promising narrow-band infrared light emitter. However, the electroluminescence of CdHgSe-based nanocrystals has remained largely unexplored, despite their potential for emitting light in the telecom wavelength range. Further benefits to their optical properties are expected from their shape control, in particular the formation of 2D nanocrystals, as well as from a proper design of their heterostructures. In this work, a colloidal synthesis of CdHgSe/ZnCdS core/shell nanoplatelets (NPLs) starting from CdSe template NPLs employing a cation exchange strategy is developed. The heterostructures synthesized exhibit photoluminescence that can be tuned from ≈1300 to 1500 nm. These near-infrared-active NPLs are employed in light-emitting diodes, demonstrating low turn-on voltage and high external quantum efficiency.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37991) publication
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Advanced Functional Materials 24(2024), 2310067
DOI: 10.1002/adfm.202310067
Cited 8 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37991
Low-temperature diffusion in thin-film Pt-(Au-)-Co heterostructures: a structural and magnetic characterization
Pedan, R.; Makushko, P.; Yavorskyi, Y.; Dubikovskyi, O.; Bodnaruk, A.; Burmak, A.; Golub, V.; Voloshko, S.; Hübner, R.; Makarov, D.; Igor, V.
Abstract
Formation of functional thin films for nanoelectronics and magnetic data storage via thermally induced diffusion-driven structural phase transformations in multilayer stacks is a promising technology-relevant approach. Ferromagnetic thin films based on Co Pt alloys are considered as a material science platform for the development of various applications such as spin valves, spin orbit torque devices, and high-density data storage media. Here, we study diffusion processes in Pt-Co-based stacks with the focus on the effect of layers inversion (Pt/Co/substrate vs. Co/Pt/substrate) and insertion of an intermediate Au layer on the structural transitions and magnetic properties. We demonstrate that layer stacking has a pronounced effect on the diffusion rate at temperatures, where the diffusion is dominated by grain boundaries. We quantify effective diffusion coefficients, which characterize the diffusion rate of Co and Pt through the interface and grain boundaries, providing the possibility to control the homogenization rate of Pt-Co-based heterostructures. The obtained values are in the range of 10-16 – 10-13 cm2/s for temperatures of 150 °C – 350 °C. Heat treatment of thin-film samples results in the coercivity enhancement, which is attributed to short-range chemical ordering effects. We show that introducing an additional Au intermediate layer leads to an increase of the coercive field of the annealed samples due to a modification of exchange coupling between the magnetic grains at the grain boundaries.
Keywords: diffusion coefficient; grain boundary diffusion; magnetic thin films; short-range chemical order; Co-Pt alloy
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Nanotechnology 35(2024), 195707
DOI: 10.1088/1361-6528/ad22a8
Cited 2 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37783
Structural investigations of Au-Ni aerogels: morphology and element distribution
Kresse, J.; Georgi, M.; Hübner, R.; Eychmüller, A.
Abstract
The physical properties of nanomaterials are determined by their structural features, making accurate structural control indispensable. This carries over to future applications. In the case of metal aerogels, highly porous networks of aggregated metal nanoparticles, such precise tuning is still largely pending. Although recent improvements in controlling synthesis parameters like electrolytes, reductants, or mechanical stirring, the focus has always been on one particular morphology at a time. Meanwhile, complex factors, such as morphology and element distributions, are studied rather sparsely. We demonstrate the capabilities of precise morphology design by deploying Au-Ni, a novel element combination for metal aerogels in itself, as a model system to combine common aerogel morphologies under one system for the first time. Au-Ni aerogels were synthesized via modified one- and two-step gelation, partially combined with galvanic replacement, to obtain aerogels with alloyed, heterostructural (novel metal aerogel structure of interconnected nanoparticles and nanochains), and hollow spherical building blocks. These differences in morphology are directly reflected in the physisorption behavior, linking the isotherm shape and pore size distribution to the structural features of the aerogels, including a broad-ranging specific surface area (35-65 m2 g-1). The aerogels were optimized regarding metal concentration, destabilization, and composition, revealing some delicate structural trends regarding the ligament size and hollow sphere character. Hence, this work significantly improves the structural tailoring of metal aerogels and possible up-scaling. Lastly, preliminary ethanol oxidation tests demonstrated that morphology design extends to the catalytic performance. All in all, this work emphasizes the strengths of morphology design to obtain optimal structures, properties, and (performances) for any material application.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37674) publication
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Nanoscale Advances 5(2023), 5487-5498
DOI: 10.1039/d3na00359k
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37674
Photoluminescence Properties of Lanthanide-Doped Alumina and YAG Aerogels
Metzkow, N.; Klemmed, B.; Georgi, M.; Hübner, R.; Eychmüller, A.
Abstract
In this work, the range of alumina (Al2O3) and yttrium aluminum garnet (YAG) aerogels was extended by doping them with lanthanide ions. The aerogels were synthesized by using a universal, epoxide-assisted sol−gel method. They were thermally treated to induce structural changes, which were characterized in more detail by using X-ray diffraction and electron microscopy. The alumina samples showed topotactic phase transformations from boehmite, via γ-alumina to a mixed alumina phase, while the YAG started as an amorphous mixed oxide phase, which crystallized at 1000 °C into pure crystalline YAG. In order to expand the functionalities of the aerogels, they were doped with the rare-earth ions Eu3+ and Tb3+ (3 mol %). The red or green photoluminescence could be observed only starting from a temperature treatment of 550 °C, which can be related to the defect reduction and crystallinity increase due to phase transformations and sintering processes occurring. For the first time, the photoluminescence quantum yields of luminescent aerogels could be determined. The highest quantum yield of 25.5 ± 1.1 % was achieved for the Al2O3-Tb-1000 sample.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37493) publication
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Journal of Physical Chemistry C 127(2023), 16995-17001
DOI: 10.1021/acs.jpcc.3c05011
Cited 3 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37493
Leveraging Ligand and Composition Effects: Morphology-Tailorable Pt–Bi Bimetallic Aerogels for Enhanced (Photo-)Electrocatalysis
Xue, G.; Li, Y.; Du, R.; Wang, J.; Hübner, R.; Gao, M.; Hu, Y.
Abstract
Metal aerogels (MAs) are emerging porous materials displaying unprecedented potential in catalysis, sensing, plasmonic technologies, etc. However, the lack of efficient regulation of their nano-building blocks (NBBs) remains a big hurdle that hampers the in-depth investigation and performance enhancement. Here, by harmonizing composition and ligand effects, Pt- and Bi-based single- and bimetallic aerogels bearing NBBs of controlled dimensions and shapes are obtained by facilely tuning the metal precursors and the applied ligands. Particularly, by further modulating the electronic and optic properties of the aerogels via adjusting the content of the catalytically active Pt component and the semiconducting Bi component, both the electrocatalytic and photoelectrocatalytic performance of the Pt–Bi aerogels can be manipulated. In this light, an impressive catalytic performance for electro-oxidation of methanol is acquired, marking a mass activity of 6.4-fold higher under UV irradiation than that for commercial Pt/C. This study not only sheds light on in situ manipulating NBBs of MAs, but also puts forward guidelines for crafting high-performance MAs-based electrocatalysts and photoelectrocatalysts toward energy-related electrochemical processes.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37466) publication
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Small 19(2023), 2301288
DOI: 10.1002/smll.202301288
Cited 6 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37466
Room-temperature extended short-wave infrared GeSn photodetectors realized by ion beam techniques
Wen, S.; Shaikh, M. S.; Steuer, O.; Prucnal, S.; Grenzer, J.; Hübner, R.; Turek, M.; Pyszniak, K.; Reiter, S.; Fischer, I. A.; Georgiev, Y.; Helm, M.; Wu, S.; Luo, J.-W.; Zhou, S.; Berencen, Y.
Abstract
GeSn alloys hold great promise as high-performance, low-cost, near- and short-wavelength infrared photodetectors with the potential to replace the relatively expensive and currently market-dominant InGaAs- and InSb-based photodetectors. In this Letter, we demonstrate room-temperature GeSn pn photodetectors fabricated by a complementary metal-oxide-semiconductor compatible process, involving Sn and P ion implantation and flash-lamp annealing prior to device fabrication. The fabrication process enables the alloying of Ge with Sn at concentrations up to 4.5% while maintaining the high-quality single-crystalline structure of the material. This allows us to create Ge0.955Sn0.045 pn photodetec-tors with a low dark current density of 12.8 mA/cm2 and a relatively high extended responsivity of 0.56 A/W at 1.71 l m. These results pave the way for the implementation of a cost-effective, scalable, and CMOS-compatible short-wavelength infrared detector technology.
Keywords: Semiconductors; Photodetectors; GeSn; Implantation; Flash-lamp annealing
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37456) publication
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Applied Physics Letters 123(2023), 081109
DOI: 10.1063/5.0166799
Cited 5 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-37456
Novel Mixed-Dimensional hBN-Passivated Silicon Nanowire Reconfigurable Field Effect Transistors: Fabrication and Characterization
Ghosh, S.; Bilal Khan, M.; Chava, P.; Watanabe, K.; Taniguchi, T.; Prucnal, S.; Hübner, R.; Mikolajick, T.; Erbe, A.; Georgiev, Y.
Abstract
This work demonstrates the novel concept of a mixed-dimensional reconfigurable field effect transistor (RFET) by combining a one-dimensional (1D) channel material such as a silicon (Si) nanowire with a two-dimensional (2D) material as a gate dielectric. An RFET is an innovative device that can be dynamically programmed to perform as either an n- or p-FET by applying appropriate gate potentials. In this work, an insulating 2D material, hexagonal boron nitride (hBN), is introduced as a gate dielectric and encapsulation layer around the nanowire in place of a thermally grown or atomic-layer-deposited oxide. hBN flake was mechanically exfoliated and transferred onto a silicon nanowire-based RFET device using the dry viscoelastic stamping transfer technique. The thickness of the hBN flakes was investigated by atomic force microscopy and transmission electron microscopy. The ambipolar transfer characteristics of the Si-hBN RFETs with different gating architectures showed a significant improvement in the device’s electrical parameters due to the encapsulation and passivation of the nanowire with the hBN flake. Both n- and p-type characteristics measured through the top gate exhibited a reduction of hysteresis by 10–20 V and an increase in the on–off ratio (ION/IOFF) by 1 order of magnitude (up to 108) compared to the values measured for unpassivated nanowire. Specifically, the hBN encapsulation provided improved electrostatic top gate coupling, which is reflected in the enhanced subthreshold swing values of the devices. For a single nanowire, an improvement up to 0.97 and 0.5 V/dec in the n- and p-conduction, respectively, is observed. Due to their dynamic switching and polarity control, RFETs boast great potential in reducing the device count, lowering power consumption, and playing a crucial role in advanced electronic circuitry. The concept of mixed-dimensional RFET could further strengthen its functionality, opening up new pathways for future electronics.
Keywords: mixed-dimensional reconfigurable FET; ambipolar; nickel silicide; flash lamp annealing; hBN encapsulation; subthreshold swing
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37438) publication
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ACS Applied Materials and Interfaces 15(2023)34, 40709-40718
DOI: 10.1021/acsami.3c04808
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37438
Ferromagnetic interlayer coupling in CrSBr crystals irradiated by ions
Long, F.; Ghorbani Asl, M.; Mosina, K.; Li, Y.; Lin, K.; Ganss, F.; Hübner, R.; Sofer, Z.; Dirnberger, F.; Kamra, A.; Krasheninnikov, A.; Prucnal, S.; Helm, M.; Zhou, S.
Abstract
Layered magnetic materials are becoming a major platform for future spin-based applications. Particularly the air-stable van der Waals compound CrSBr is attracting considerable interest due to its prominent magneto-transport and magneto-optical properties. In this work, we observe a transition from antiferromagnetic to ferromagnetic behavior in CrSBr crystals exposed to high-energy, non-magnetic ions. Already at moderate fluences, ion irradiation induces a remanent magnetization with hysteresis adapting to the easy-axis anisotropy of the pristine magnetic order up to a critical temperature of 110 K. Structure analysis of the irradiated crystals in conjunction with density functional theory calculations suggest that the displacement of constituent atoms due to collisions with ions and the formation of interstitials favors ferromagnetic order between the layers.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37419) publication
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Nano Letters 23(2023)18, 8468-8473
DOI: 10.1021/acs.nanolett.3c01920
Cited 11 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37419
Exploring Antibacterial Activity and Bacterial-Mediated Allotropic Transition of Differentially Coated Selenium Nanoparticles
Ruiz-Fresneda, M. A.; Schaefer, S.; Hübner, R.; Fahmy, K.; Merroun, M. L.
Abstract
The use of metal nanoparticles (NPs) as antimicrobial agents has become a promising alternative to the problem of antibiotic-resistant bacteria and other applications. Silver nanoparticles (AgNPs) are well-known as one of the most universal biocide compounds. However, selenium nanoparticles (SeNPs) recently gained more attention as effective antimicrobial agents. This study aims to investigate the antibacterial activity of SeNPs with different surface coatings (BSA-coated, chitosan-coated, and undefined coating) on the Gram-negative Stenotrophomonas bentonitica and the Gram-positive Lysinibacillus sphaericus in comparison to AgNPs. The tested NPs had similar properties, including shape (spheres), structure (amorphous), and size (50−90 nm), but differed in their surface charge. Chitosan SeNPs exhibited a positive surface charge, while the remaining NPs assayed had a negative surface charge. We have found that cell growth and viability of both bacteria were negatively affected in the presence of the NPs, as indicated by microcalorimetry and flow cytometry. Specifically, undefined coating SeNPs displayed the highest percentage values of dead cells for both bacteria (85−91%). An increase in reactive oxygen species (ROS) production was also detected. Chitosan-coated and undefined SeNPs caused the highest amount of ROS (299.7 and 289% over untreated controls) for S. bentonitica and L. sphaericus, respectively. Based on DNA degradation levels, undefined-SeNPs were found to be the most hazardous, causing nearly 80% DNA degradation. Finally, electron microscopy revealed the ability of the cells to transform the different SeNP types (amorphous) to crystalline SeNPs (trigonal/monoclinical Se), which could have environmentally positive implications for bioremediation purposes and provide a novel green method for the formation of crystalline SeNPs. The results obtained herein demonstrate the promising potential of SeNPs for their use in medicine as antimicrobial agents, and we propose S. bentonitica and L. sphaericus as candidates for new bioremediation strategies and NP synthesis with potential applications in many fields.
Keywords: selenium; nanoparticles; antibiotic; bioremediation; applications
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37231) publication
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ACS Applied Materials and Interfaces 15(2023), 29958-29970
DOI: 10.1021/acsami.3c05100
Cited 14 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37231
Europium(III) as luminescence probe for interactions of a sulfate-reducing microorganism with potentially toxic metals
Hilpmann, S.; Moll, H.; Drobot, B.; Vogel, M.; Hübner, R.; Stumpf, T.; Cherkouk, A.
Abstract
Microorganisms show a high affinity for trivalent actinides and lanthanides, which play an important role in the safe disposal of high-level radioactive waste as well as in the mining of various rare earth elements. The interaction of the lanthanide Eu(III) with the sulfate-reducing microorganism Desulfosporosinus hippei DSM 8344T, a representative of the genus Desulfosporosinus that naturally occurs in clay rock and bentonite, was in-vestigated. Eu(III) is often used as a non-radioactive analogue for the trivalent actinides Pu(III), Am(III), and Cm(III), which contribute to a major part of the radiotoxicity of the nuclear waste. D. hippei DSM 8344T showed a weak interaction with Eu(III), most likely due to a complexation with lactate in artificial Opalinus Clay pore water. Hence, a low removal of the lanthanide from the supernatant was observed. Scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy revealed a bioprecipitation of Eu(III) with phosphates potentially excreted from the cells. This demonstrates that the ongoing interaction mechanisms are more complex than a sim-ple biosorption process. The bioprecipitation was also verified by luminescence spec-troscopy, which showed that the formation of the Eu(III) phosphate compounds starts almost immediately after the addition of the cells. Moreover, chemical microscopy pro-vided information on the local distribution of the different Eu(III) species in the formed cell aggregates. These results provide first insights into the interaction mechanisms of Eu(III) with sulfate-reducing bacteria and contribute to a comprehensive safety concept for a high-level radioactive waste repository, as well as to a better understanding of the fate of heavy metals (especially rare earth elements) in the environment.
Keywords: Europium(III) luminescence; Sulfate-reducing bacteria; Europium(III) bioprecipitation; Opalinus Clay pore water
Verknüpfte Publikationen
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Data publication: Europium(III) as luminescence probe for interactions of a …
ROBIS: 37168 HZDR-primary research data are used by this (Id 37162) publication -
Data publication: Europium(III) as luminescence probe for interactions of a …
RODARE: 2357 HZDR-primary research data are used by this (Id 37162) publication
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Ecotoxicology and Environmental Safety 264(2023), 115474
DOI: 10.1016/j.ecoenv.2023.115474
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37162
Influence of engineered roughness microstructures on adhesion and turbulent resuspension of microparticles
Banari, A.; Graebe, K.; Rudolph, M.; Mohseni, E.; Lorenz, P.; Zimmer, K.; Hübner, R.; Henry, C.; Bossy, M.; Hampel, U.; Lecrivain, G.
Abstract
From microplastics resuspending into the atmosphere to earth particles left behind during extraterrestrial explorations, the resuspension of microparticles by a turbulent gas flow occurs in many natural and industrial systems. Wall surfaces, onto which particles initially adhere, are rarely smooth and this surface roughness affects their resuspension. Available experimental data on particle resuspension have been obtained with substrates, whose surfaces are either unaltered or manually abraded with, for instance, sand blasting. In these experiments, the roughness elements span a wide size range and are in-homogeneously distributed in space. Surface functionalization is a modern technique allowing the precise fabrication of a wall surface with well-characterized microstructures, hence reducing the asperity randomness associated with conventional abrasion techniques. Taking advantage of surface functionalization, we present here a new set of reference data, where the wall asperities are represented by a structured arrangement of micropillars and microcubes. Adhesion force measurements and particle remaining fraction against gas velocity, at Reynolds number up to 8000, are reported for one reference and two artificially roughened substrates. Laboratory measurements show that the microasperities have little to moderate effect on the mean adhesion force and the threshold velocity, at which half of the 100-µm particles resuspend. The standard deviations are, however, significantly affected. The presented results will primary contribute to the improvement of resuspension models, which until now rely on a simplified representation of the surface roughness elements. The presented measurements are highly compatible with such models, which involve elementary roughness features, such as hemispherical asperities superimposed with a flat plate.
Keywords: Particle resuspension; Adhesion force measurement; Turbulent gas flow; Surface functionalization; Surface roughness
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Raw data related to publication "Influence of engineered roughness …
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Raw data related to publication "Influence of engineered roughness …
RODARE: 2426 HZDR-primary research data are used by this (Id 37161) publication
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Journal of Aerosol Science 174(2023), 106258
DOI: 10.1016/j.jaerosci.2023.106258
Cited 2 times in Scopus
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Bimetallic Pt-Hg Aerogels for Electrocatalytic Upgrading of Ethanol to Acetate
Zhang, X.; Wang, T.; Wang, C.; Hübner, R.; Eychmüller, A.; Zhan, J.; Cai, B.
Abstract
Electrochemical upgrading of ethanol to acetic acid provides a promising strategy to couple with the current hydrogen production from water electrolysis. This work reports the design of a series of bimetallic Pt-Hg aerogels, where the PtHg aerogel exhibits a 10.5-times higher mass activity than that of commercial Pt/C toward ethanol oxidation. More impressively, the PtHg aerogel demonstrates nearly 100% selectivity toward the production of acetic acid. The operando infrared spectroscopic studies and nuclear magnetic resonance analysis verify the preferable C2 pathway mechanism during the reaction. This work opens an avenue for the electrochemical synthesis of acetic acid via ethanol electrolysis.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37115) publication
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Small 19(2023), 2207557
DOI: 10.1002/smll.202207557
Cited 9 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37115
Alloyed RexMo1 − xS2 Nanoflakes with Enlarged Interlayer Distances for Hydrogen Evolution
Li, J.; Hübner, R.; Deconinck, M.; Bora, A.; Göbel, M.; Schwarz, D.; Chen, G.; Wang, G.; Yang, S. A.; Vaynzof, Y.; Lesnyak, V.
Abstract
Molybdenum sulfide (MoS2) has attracted significant attention due to its great potential as a low-cost and efficient catalyst for the hydrogen evolution reaction. Developing a facile, easily upscalable, and inexpensive approach to produce catalytically active nanostructured MoS2 with a high yield would significantly advance its practical application. Colloidal synthesis offers several advantages over other preparation techniques to overcome the low reaction yield of exfoliation and drawbacks of expensive equipment and processes used in chemical vapor deposition. In this work, we report an efficient synthesis of alloyed RexMo1−xS2 nanoflakes with an enlarged interlayer distance, among which the composition Re0.55Mo0.45S2 exhibits excellent catalytic performance with overpotentials as low as 79 mV at 10 mA/cm2 and a small Tafel slope of 42 mV/dec. Density functional theory calculations prove that enlarging the distance between layers in the RexMo1−xS2 alloy can greatly improve its catalytic performance due to a significantly reduced free energy of hydrogen adsorption. The developed approach paves the way to design advanced transition metal dichalcogenide-based catalysts for hydrogen evolution and to promote their large-scale practical application.
Keywords: RexMo1−xS2 alloys; enlarged interlayer distance; nanoflakes; colloidal synthesis; hydrogen evolution
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37098) publication
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ACS Applied Nano Materials 6(2023), 9475-9483
DOI: 10.1021/acsanm.3c01163
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37098
B20 Weyl semimetal CoSi film fabricated by flash-lamp annealing
Li, Z.; Yuan, Y.; Hübner, R.; Rebohle, L.; Zhou, Y.; Helm, M.; Nielsch, K.; Prucnal, S.; Zhou, S.
Abstract
B20-CoSi is a newly discovered Weyl semimetal that crystallizes into a non-centrosymmetric crystal structure. However, the investigation of B20-CoSi has so far been focused on bulk materials, whereas the growth of thin films on technology-relevant substrates is a prerequisite for most practical applications. In this study, we have used millisecond-range flash-lamp annealing, a non-equilibrium solid-state reaction, to grow B20-CoSi thin films. By optimizing the annealing parameters, we were able to obtain thin films with a pure B20-CoSi phase. The magnetic and transport measurements indicate the appearance of the charge density wave and the chiral anomaly. Our work presents a promising method for preparing thin films of most binary B20 transition-metal silicides, which are candidates for topological Weyl semimetals.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37062) publication
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ACS Applied Materials and Interfaces 15(2023)25, 30517-30523
DOI: 10.1021/acsami.3c05634
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37062
Scalable and Controllable Synthesis of Pt-Ni Bunched-Nanocages Aerogels as Efficient Electrocatalysts for Oxygen Reduction Reaction
Zheng, Y.; Petersen, A. S.; Wan, H.; Hübner, R.; Zhang, J.; Wang, J.; Qi, H.; Ye, Y.; Liang, C.; Yang, J.; Cui, Z.; Meng, Y.; Zheng, Z.; Rossmeisl, J.; Liu, W.
Abstract
Developing efficient and stable Pt-based oxygen reduction reaction (ORR) electrocatalysts via both economical and controllable routes is critical for the
practical application of electrochemical energy devices. Herein, a scalable, controllable, and general ambient-O2-involved aqueous-solution cultivating strategy to prepare PtxMy (M = Ni, Fe, Co) bunched-nanocages aerogels (BNCs AG) is demonstrated, based on a newly established high-M-to-Pt-precursor-ratio-and-B-incorporation-facilitated M-rich core and Pt-rich shell hydrogel formation process. The Pt83Ni17 BNCs AG shows prominent ORR performance with a mass activity (MA) of 1.95 A mgPt
−1 and specific activity of 3.55 mA cm−2, which are 8.9-times and 9.6-times that of Pt supported on carbon (Pt/C), respectively. Particularly,
the Pt83Ni17 BNCs AG displays greatly enhanced durability (MA 82.6% retention) compared to Pt/C (MA 31.8% retention) after a 20 000-cycles accelerated durability test. Systematic studies including density functional theory calculations uncover that the excellent activity is closely related to the optimized ligand and strain effects with the optimized Ni content in this aerogel; the outstanding durability is endowed by the lowered-down Ni leaching with the optimized Pt/Ni ratio and the inhibited sintering due to its appropriate porosity. This work provides new perspectives on the development of electrocatalysts with both high performance and low cost.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37026) publication
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Advanced Energy Materials 13(2023), 2204257
DOI: 10.1002/aenm.202204257
Cited 41 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37026
Composition-Dependent Optical Properties of Cu−Zn−In−Se Colloidal Nanocrystals Synthesized via Cation Exchange
Bora, A.; Lox, J.; Hübner, R.; Weiß, N.; Bahmani Jalali, H.; Di Stasio, F.; Steinbach, C.; Gaponik, N.; Lesnyak, V.
Abstract
Copper chalcogenide-based nanocrystals (NCs) are a suitable replacement for toxic Cd/Pb chalcogenide-based NCs in a wide range of applications including photovoltaics, optoelectronics, and biological imaging. However, despite rigorous research, direct synthesis approaches of this class of compounds suffer from inhomogeneous size, shape, and composition of the NC ensembles, which is reflected in their broad photoluminescence (PL) bandwidths. A partial cation exchange (CE) strategy, wherein host cations in the initial binary copper chalcogenide are replaced by incoming cations to form ternary/quaternary multicomponent NCs, has been proven to be instrumental in achieving better size, shape, and composition control to this class of
nanomaterials. Additionally, adopting synthetic strategies which help to eliminate inhomogeneities in the NC ensembles can lead to narrower PL bandwidths, as was shown by single-particle studies on I−III−VI2-based semiconductor NCs. In this work, we formulate a two-step colloidal synthesis of Cu−Zn−In−Se (CZISe) NCs via a partial CE pathway. The first step is the synthesis of Cu2−xSe NCs, which serve as a template for the subsequent CE reaction. The second step is the incorporation of the In3+ and Zn2+ guest cations into the synthesized Cu2−xSe NCs via simultaneous injection of both metal precursors, which results in gradient-alloyed CZISe NCs with a Zn-rich surface. The as-synthesized NCs exhibit near-infrared (NIR) PL without an additional shell growth, which is typically required in most of the developed protocols. The photoluminescence quantum yield (PLQY) of these Cu chalcogenide-based NCs reaches 20%. These NCs also exhibit intriguingly narrow PL bands, which challenges the notion of broad PL bands being an inherent property of this class of NCs. Additionally, a variation in the feed ratios of the incoming cations, i.e., In/Zn, results in the variation of the composition of the synthesized NCs. Henceforth, the optical properties of these NCs could be tuned by a simple variation of the composition of the NCs achieved by varying the feed ratios of the incoming cations. Within a narrow size distribution, the PL maxima range from 980 to 1060 nm, depending on the composition of the NCs. Post-synthetic surface modification of the synthesized NCs enabled the replacement of the parent long-chain organic ligands with smaller species, which is essential for their prospective applications requiring efficient charge transport. With PL emission extended into the NIR, the synthesized NCs are suitable for an array of potential applications, most importantly in the area of solar energy harvesting and bioimaging. The large Stokes shift inherent to these materials, their absorption in the solar range, and their NIR PL within the biological window make them suitable candidates.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 37009) publication
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Chemistry of Materials 35(2023), 4068-4077
DOI: 10.1021/acs.chemmater.3c00538
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-37009
Interaction of domain walls with grain boundaries in uniaxial insulating antiferromagnets
Pylypovskyi, O.; Hedrich, N.; Tomilo, A.; Kosub, T.; Wagner, K.; Hübner, R.; Shields, B.; Sheka, D.; Faßbender, J.; Maletinsky, P.; Makarov, D.
Abstract
A search for high-speed and low-energy memory devices puts antiferromagnetic thin films at the forefront of spintronic research. Here, we develop a material model of a granular antiferromagnetic thin film with uniaxial anisotropy and provide fundamental insight into the interaction of antiferromagnetic domain walls with grain boundaries. This model is validated on thin films of the antiferromagnetic insulator \ch{Cr2O3}, revealing complex maze-like domain patterns hosting localized nanoscale domains down to 50 nm. We show that the inter-grain magnetic parameters can be estimated based on an analysis of high-resolution images of antiferromagnetic domain patterns examining the domain patterns' self-similarity and the statistical distribution of domain sizes. Having a predictive material model and understanding of the pinning of domain walls on grain boundaries, we put forth design rules to realize granular antiferromagnetic recording media.
Keywords: antiferromagnetism; granular media; spin-lattice simulations; Nitrogen vacancy magnetometry
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Physical Review Applied 20(2023), 014020
DOI: 10.1103/PhysRevApplied.20.014020
Cited 2 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36982
Investigations towards incorporation of Eu3+ and Cm3+ during ZrO2 crystallization in aqueous solution
Opitz, L.; Hübner, R.; Shams Aldin Azzam, S.; Gilson, S.; Finkeldei, S. C.; Huittinen, N. M.
Abstract
Nuclear energy provides a widely applied carbon-reduced energy source. Following operation, the spent nuclear fuel (SNF), containing a mixture of radiotoxic elements such as transuranics, needs to be safely disposed of. Safe storage of SNF in a deep geological repository (DGR) relies on multiple engineered and natural retention barriers to prevent environmental contamination. In this context, zirconia (ZrO2) formed on the SNF rod cladding, could be employed as an engineered barrier for immobilization of radionuclides via structural incorporation. This study investigates the incorporation of Eu3+ and Cm3+, representatives for trivalent transuranics, into zirconia by co-precipitation and crystallization in aqueous solution at 80 °C. Complementary structural and microstructural characterization has been carried out by Powder X-ray Diffraction (PXRD), spectrum imaging analysis based on Energy-Dispersive X-ray Spectroscopy in Scanning Transmission Electron Microscopy mode (STEM-EDXS), and luminescence spectroscopy. The results reveal the association of the dopants with the zirconia particles and elucidate the presence of distinct bulk and superficially incorporated species. Hydrothermal aging for up to 460 days in alkaline media points to great stability of these incorporated species after initial crystallization, with no indication of phase segregation or release of Eu3+ and Cm3+ over time. These results suggest that zirconia would be a suitable technical retention barrier for mobilized trivalent actinides in a DGR.
Keywords: nuclear waste management; crystallization; zirconia; incorporation; trivalent; luminescence spectroscopy; transmission electron microscopy; X-ray diffraction
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36878) publication
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Scientific Reports 13(2023), 12276
DOI: 10.1038/s41598-023-39143-0
Cited 2 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36878
Direct magnetic manipulation of a permalloy nanostructure by a focused cobalt ion beam
Pablo-Navarro, J.; Klingner, N.; Hlawacek, G.; Kakay, A.; Bischoff, L.; Narkovic, R.; Mazarov, P.; Hübner, R.; Meyer, F.; Pilz, W.; Lindner, J.; Lenz, K.
Abstract
We present results of direct maskless magnetic patterning of ferromagnetic nanostructures using a cobalt focused ion beam (FIB) system. The liquid metal ion source of the FIB was made of a Co36Nd64 alloy. A Wien mass filter allows for selecting the ion species. Using the FIB, we implanted narrow tracks of Co ions into a nominal 5000×1000×50 nm3 permalloy strip. We observed the Co-induced changes of the magnetic properties by measuring the sample with microresonator ferromagnetic resonance before and after the implantation. Regions as small as 50 nm can be implanted up to concentrations of at.-10 % near the surface. This allows for easy magnetic modification of edge-localized spin waves with a lateral resolution otherwise hard to reach. The direct-write maskless FIB process is quick and convenient for optical measurement techniques, as it does not involve the virtually impossible removal of ion-hardened resist masks one would face when using lithography with broad-beam ion implantation
Keywords: Ferromagnetic resonance; nanostructures; ferromagnetism; focused ion beams; spin-wave dynamics
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36822) publication
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Physical Review Applied 20(2023)4, 044068
DOI: 10.1103/PhysRevApplied.20.044068
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Bimetallic Pt−Ni Two-Dimensional Interconnected Networks: Developing Self-Assembled Materials for Transparent Electronics
Khavlyuk, P.; Mitrofanov, A.; Shamraienko, V.; Hübner, R.; Kresse, J.; Borchert, K. B. L.; Eychmüller, A.
Abstract
Continuous advancements in science and technology in the field of flexible devices encourage researchers to dedicate themselves to seeking candidates for new flexible transparent conductive films (FTCFs). Our recently developed two-dimensional (2D) metal aerogels are considered as a new class of FTCFs. Here, we describe a new large-scale self-assembly synthesis of bimetallic Pt-Ni 2D metal aerogels with controllable morphology during the synthesis. The
obtained 2D aerogels require only a low quantity of precursors for the synthesis of percolating nanoscale networks with areas of up to 6 cm2 without the need of an additional drying step. Stacks of the obtained monolayer structures display low sheet resistances (down to 270 Ω/sq), while decreasing the optical transparency. In perspective, the 2D bimetallic Pt-Ni aerogels not only enrich the structural diversity of metal aerogels but also bring forth new materials for further applications in flexible electronics and electrocatalysis with reduced costs of production.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36821) publication
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Chemistry of Materials 35(2023), 2864-2872
DOI: 10.1021/acs.chemmater.2c03707
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36821
Optimizing the Pd Sites in Pure Metallic Aerogels for Efficient Electrocatalytic H2O2 Production
Zhang, X.; Wang, C.; Chen, K.; Clark, A. H.; Hübner, R.; Zhan, J.; Zhang, L.; Eychmüller, A.; Cai, B.
Abstract
Decentralized electrochemical production of hydrogen peroxide (H2O2) is an attractive alternative to the industrial anthraquinone process, the application of which is hindered by the lack of high-performance electrocatalysts in acidic media. Herein, a novel catalyst design strategy is reported to optimize the Pd sites in pure metallic aerogels by tuning their geometric environments and electronic structures. By increasing the Hg content in the Pd-Hg aerogels, the Pd-Pd coordination is gradually diminished, resulting in isolated, single-atom-like Pd motifs in the Pd2Hg5 aerogel. Further heterometal doping leads to a series of M-Pd2Hg5 aerogels with an unalterable geometric environment, allowing for sole investigation of the electronic effects. Combining theoretical and experimental analyses, a volcano relationship is obtained for the M-Pd2Hg5 aerogels, demonstrating an effective tunability of the electronic structure of the Pd active sites. The optimized Au-Pd2Hg5 aerogel exhibits an outstanding H2O2 selectivity of 92.8% as well as transferred electron numbers of ≈2.1 in the potential range of 0.0-0.4 VRHE. This work opens a door for designing metallic aerogel electrocatalysts for H2O2 production and highlights the importance of electronic effects in tuning electrocatalytic performances.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36816) publication
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Advanced Materials 35(2023), 2211512
DOI: 10.1002/adma.202211512
Cited 43 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36816
Porous Magnesium Oxide by Twin Polymerization: From Hybrid Materials to Catalysis
Scharf, S.; Notz, S.; Thomas, R.; Mehring, M.; Tegenkamp, C.; Formánek, P.; Hübner, R.; Lang, H.
Abstract
Twin monomers [Mg(2-OCH2-cC6H4O)][L]0.8 (2, L=diglyme) and [Mg(2-OCH2-cC6H4O)][L]0.66 (3, L=tmeda) form by their thermal polymerization interpenetrating organic-inorganic hybrid materials in a straightforward manner. Carbonization (Ar) followed by calcination gave porous MgO (2: surface area 200 m2g-1, 3: 400 m2g-1), which showed in catalytic studies towards Meerwein-Ponndorf-Verley reductions excellent yields and complete conversions for cyclohexanone and benzaldehyde. However, with crotonaldehyde a mixture of C4–C8 compounds was obtained. When MgO was exposed to air then primarily crotyl alcohol was formed. The range of applications could be easily extended by twin polymerization of 3 in presence of [Cu-(O2CCH2O(CH2CH2O)2Me)2] (4) or [Ag(O2CCH2-cC4H3S)(PPh3)] (5), resulting in the formation of nanoparticle-decorated porous CuO@MgO or Ag@MgO materials, which showed high catalytic reactivity towards the reduction of methylene blue.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36744) publication
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European Journal of Inorganic Chemistry 26(2023), e202200663
DOI: 10.1002/ejic.202200663
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36744
Element Distributions in Bimetallic Aerogels
Wang, C.; Herranz, J.; Hübner, R.; Schmidt, T. J.; Eychmüller, A.
Abstract
Metal aerogels assembled from nanoparticles have captured grand attention because they combine the virtues of metals and aerogels and are regarded as ideal materials to address current environmental and energy issues. Among these aerogels, those composed of two metals not only display combinations (superpositions) of the properties of their individual metal components but also feature novel properties distinctly different from those of their monometallic relatives. Therefore, quite some effort has been invested in refining the synthetic methods, compositions, and structures of such bimetallic aerogels as to boost their performance for the envisaged application(s). One such use would be in the field of electrocatalysis, whereby it is also of utmost interest to unravel the element distributions of the (multi)metallic catalysts to achieve a ratio of their bottom-to-up design. Regarding the element distributions in bimetallic aerogels, advanced characterization techniques have identified alloys, core-shells, and structures in which the two metal particles are segregated (i.e., adjacent but without alloy or core-shell structure formation). While an almost infinite number of metal combinations to form bimetallic aerogels can be envisaged, the knowledge of their formation mechanisms and the corresponding element distributions is still in its infancy. The evolution of the observed musters is all but well understood, not to mention the positional changes of the elements observed in operando or in beginning- vs end-of-life comparisons (e.g., in fuel cell applications).
With this motivation, in this Account we summarize the endeavors made in element distribution monitoring in bimetallic aerogels in terms of synthetic methods, expected structures, and their evolution during electrocatalysis. After an introductory chapter, we first describe briefly the two most important characterization techniques used for this, namely, scanning transmission electron microscopy (STEM) combined with element mapping (e.g., energy-dispersive X-ray spectroscopy (EDXS)) and X-ray absorption spectroscopy (XAS). We then explain the universal methods used to prepare bimetallic aerogels with different compositions. Those are divided into one-step methods in which gels formed from mixtures of the respective metal salts are coreduced and two-step approaches in which monometallic nanoparticles are mixed and gelated. Subsequently, we summarize the current state-of-knowledge on the element distributions unraveled using diverse characterization methods. This is extended to investigations of the element distributions being altered during electrochemical cycling or other loads. So far, a theoretical understanding of these processes is sparse, not to mention predictions of element distributions. The Account concludes with a series of remarks on current challenges in the field and an outlook on the gains that the field would earn from a solid understanding of the underlying processes and a predictive theoretical backing.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36524) publication
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Accounts of Chemical Research 56(2023), 237-247
DOI: 10.1021/acs.accounts.2c00491
Cited 19 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36524
Bottom-up Fabrication of FeSb₂ Nanowires on Crystalline GaAs Substrates with Ion-induced Pre-patterning
Weinert, T.; Erb, D.; Hübner, R.; Facsko, S.
Abstract
Most industrial processes are generating waste heat that can be converted into electrical energy with thermoelectric generators (TEGs). For efficient energy harvesting, it is necessary to significantly improve the properties like Seebeck coefficient, electrical and thermal conductivity of the thermoelectric materials in the TEGs. One promising approach are thermoelectric nanostructures to reduce the thermal conductivity while maintaining constant electrical conductivity and Seebeck coefficient. For that reason, this study investigated the possibility of preparing nanowires of the thermoelectric material iron antimonide (FeSb₂) on crystalline gallium arsenide GaAs(001) substrates with ion-induced surface nanopatterning.
The GaAs(001) substrates were pre-patterned using 1 keV Ar⁺ ion irradiation. By using an ion source with a broad, unfocused ion beam at normal incidence, the patterned area can be scaled to nearly any size. The self-organized surface structure is formed by reverse epitaxy and is characterized by almost perfectly parallel-aligned ripples at the nanometer scale. For the fabrication of FeSb₂ nanowires, iron and antimony were successively deposited on the prepatterned GaAs substrates at grazing incidence and then annealed. They were characterized using transmission electron microscopy (TEM), in particular high-resolution TEM imaging for structure analysis and spectrum imaging analysis based on energy-dispersive X-ray spectroscopy
for element characterization.
With the presented fabrication method, FeSb₂ nanowires were produced successfully on GaAs(001) substrates with an ion-induced nanopatterned surface. The nanowires have a polycristalline structure and a cross-sectional area which is scalable up to 22×22nm². Due to the highly ordered nanostructure of the GaAs substrates, the nanowires have a length of several micrometer. These bottom-up nanofabrication based on ion-induced patterning can be a viable alternative to top-down procedures regarding to efficiency and costs.
Keywords: bottom-up nanofabrication; ion-induced nanopatterning; physical vapor deposition; transmission electron microscopy; energy-dispersive X-ray spectroscopy
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36264) publication
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Data publication: Bottom-up Fabrication of FeSb₂ Nanowires on Crystalline GaAs …
ROBIS: 36517 HZDR-primary research data are used by this (Id 36264) publication
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Frontiers in Physics 11(2023), 1149608
DOI: 10.3389/fphy.2023.1149608
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Fabrication of highly n-type-doped germanium nanowires and Ohmic contacts using ion implantation and flash lamp annealing
Echresh, A.; Prucnal, S.; Li, Z.; Hübner, R.; Ganss, F.; Steuer, O.; Bärwolf, F.; Jazavandi Ghamsari, S.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.
Abstract
Accurate control of doping and fabrication of metal contacts on n-type germanium nanowires (GeNWs) with low resistance and linear characteristics remain a major challenge in germanium-based nanoelectronics. Here, we present a combined approach to fabricate Ohmic contacts on n-type-doped GeNWs. Phosphorus (P) implantation followed by millisecond rear-side flash lamp annealing was used to produce highly n-type doped Ge with an electron concentration in the order of 10^19 − 10^20 cm^(−3). Electron beam lithography, inductively coupled plasma reactive ion etching, and nickel (Ni) deposition were used to fabricate GeNW-based devices with symmetric Hall bar configuration, which allows detailed electrical characterization of the NWs. Afterward, rear-side flash lamp annealing was applied to form Ni germanide at the Ni-GeNWs contacts to reduce the Schottky barrier height. The two-probe current-voltage measurements on n-type-doped GeNWs exhibit linear Ohmic behavior. Also, the size-dependent electrical measurements showed that carrier scattering near the NW surfaces and reduction of the effective NW cross-section dominate the charge transport in the GeNWs.
Keywords: Germanium nanowires; ion implantation; flash lamp annealing; n-type doped; Ohmic contacts; Hall bar configuration
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36230) publication
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Fabrication of highly n-type-doped germanium nanowires and Ohmic contacts …
ROBIS: 34995 HZDR-primary research data are used by this (Id 36230) publication -
Fabrication of highly n-type-doped germanium nanowires and Ohmic contacts …
RODARE: 1824 HZDR-primary research data are used by this (Id 36230) publication
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ACS Applied Electronic Materials 4(2022), 5256-5266
DOI: 10.1021/acsaelm.2c00952
Cited 2 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-36230
Influence of substrate composition on size and chemical state of ion beam synthesised Co nanoparticles – Towards fabrication of electrodes for energy devices
Gupta, P.; Jovic, V.; Hübner, R.; Anquillare, E.; Suschke, K.; Smith, K. E.; Markwitz, A.; Waterhouse, G. I. N.; Kennedy, J.
Abstract
A one-step approach to synthesize ultrafine transition metal particles (size < 5 nm) in carbon substrates is highly desirable for fabricating electrodes for energy devices. Herein, cobalt ion implantation into amorphous carbon films (a:C) and hydrogenated amorphous carbon films (a:CH) was explored, with the aim of synthesizing ultrafine metallic cobalt nanoparticles at room temperature. Co ions of 30 keV energy were implanted into the carbon films to achieve a Co areal density of 1.0 ± 0.1 × 1017 atoms cm-2. Rutherford backscattering measurements revealed that hydrogenated amorphous carbon films gave a broader Co depth distribution compared to the amorphous carbon films. Further, cross-sectional TEM analysis revealed that hydrogenated carbon films suppressed metallic Co nanoparticle aggregation, leading to the creation of ultrafine Co nanoparticles (size < 5 nm). Co L-edge X-ray absorption spectroscopy measurements confirmed the formation of predominantly metallic Co nanoparticles by ion implantation. Results conclusively demonstrate that the presence of hydrogen (~ 28 at %) in the carbon matrix facilitates the synthesis of ultrafine metallic Co nanoparticles during Co ion implantation.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36209) publication
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Materials Today Communications 34(2023), 105235
DOI: 10.1016/j.mtcomm.2022.105235
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36209
A Decade of Electrocatalysis with Metal Aerogels: A Perspective
Li, W.; Weng, B.; Sun, X.; Cai, B.; Hübner, R.; Luo, Y.; Du, R.
Abstract
Nowadays, great efforts have been spent on addressing concerns over energy and environmental crises. Among these efforts, electrocatalysis is widely recognized and studied for its high efficiency and easy processability. As a class of emerging electrocatalysts, metal aerogels (MAs) stand out in the last decade. In virtue of their three‐dimensional conductive pathways, their library of catalytically/optically active sites, and their robust network structures, MAs have unique advantages in electrocatalysis. However, due to the short history of MAs, there is insufficient research on them, leaving significant room for material design and performance optimization. This perspective will mainly focus on electrocatalysis with MAs, aiming to summarize the state‐of‐the‐art progress and to guide the on‐target design of efficient MAs‐based electrocatalysts towards energy‐ and environment‐related applications.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36184) publication
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Catalysts 13(2023)1, 167
DOI: 10.3390/catal13010167
Cited 12 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36184
Tailored Particle Catalysts for Multistep One-pot Chemoenzymatic Cascade in Pickering Emulsions
Wang, S.; Scandurra, L.; Hübner, R.; Gro Nielsen, U.; Wu, C.
Abstract
Chemoenzymatic cascades are an important tool for advanced synthesis in chemistry. However, these cascades are often limited due to the incompatibility issue between two distinct catalysts and reactions. To address this issue, we present a simple multistep one-pot platform, in which nanoparticle catalysts are prepared to allow chemo- and biocatalytic reactions performed sequentially in water and Pickering emulsions. The preparation of particle catalysts is accomplished in just two steps by polymer modifications and [RuCl2(pcymene)]2 coordination, while the benefits of using them for chemoenzymatic synthesis are multifaceted. They act not only as asymmetric catalysts for asymmetric transfer hydrogenation from acetophenone to 1-phenylethanol in water with up to 99 % conversion and 93 % ee, but also as an emulsifier to form stable Pickering emulsions. By the addition of Candida antarctica lipase B into the emulsions, the second-step reaction of enantioselective acylation was achieved with 38 % conversion and 99 % ee. Therefore, we successfully present a simple method to enable chemoenzymatic cascades by combining particle catalysts and enzymes in water and Pickering emulsions in a sequential fashion, which can be generalized for other cascade syntheses with different chemo- and biocatalysts in the future.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36167) publication
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ChemCatChem 15(2023), e202201229
Online First (2022) DOI: 10.1002/cctc.202201229
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36167
Interparticle Charge-Transport-Enhanced Electrochemiluminescence of Quantum-Dot Aerogels
Gao, X.; Jiang, G.; Gao, C.; Prudnikau, A.; Hübner, R.; Zhan, J.; Zou, G.; Eychmüller, A.; Cai, B.
Abstract
Electrochemiluminescence (ECL) represents a widely explored technique to generate light, in which the emission intensity relies critically on the charge-transfer reactions between electrogenerated radicals. Two types of charge-transfer mechanisms have been postulated for ECL generation, but the manipulation and effective probing of these routes remain a fundamental challenge. Here, we demonstrate the design of quantum dot (QD) aerogels as novel ECL luminophores via a versatile water-induced gelation strategy. The strong electronic coupling between adjacent QDs enables efficient charge transport within the aerogel network, leading to the generation of highly efficient ECL based on the selectively improved interparticle chargetransfer route. This mechanism is further verified by designing CdSe-CdTe mixed QD aerogels, where the two mechanistic routes are clearly decoupled for ECL generation. We anticipate our work will advance the fundamental understanding of ECL and prove useful for designing next-generation QD-based devices.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36048) publication
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Angewandte Chemie - International Edition 62(2023), e202214487
Online First (2022) DOI: 10.1002/anie.202214487
Cited 28 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36048
WAlSiN-based solar selective coating stability-study under heating and cooling cycles in vacuum up to 800 °C using in situ Rutherford backscattering spectrometry and spectroscopic ellipsometry
Niranjan, K.; Krause, M.; Lungwitz, F.; Munnik, F.; Hübner, R.; Pemmasani, S. P.; Escobar Galindo, R.; Barshilia, H. C.
Abstract
In situ Rutherford Backscattering Spectrometry (RBS) and Spectroscopic Ellipsometry (SE) were applied to study the compositional and optical stability of a WAlSiN-based solar-selective coating (SSC) at high temperatures in vacuum. The samples were exposed to heating-cooling cycles between quasi room temperature and stepwise-increased high temperatures of 450 °C, 650 °C, and 800 °C, respectively. In situ RBS revealed full compositional stability of the SSC during thermal cycling. In situ SE indicated full conservation of the optical response at 450 °C and 650 °C, and minimal changes at 800 °C. The analysis of the ex situ optical reflectance spectra after the complete thermal cycling gave an unchanged solar absorptance of 0.94 and a slightly higher calculated thermal emittance at 800 °C of 0.16 compared to 0.15 after deposition. Cross-sectional element distribution analysis performed in scanning transmission electron microscopy mode confirmed the conservation of the SSC’s microstructure after the heating – cooling cycles. The study demonstrates compositional, optical, and structural stability of the WAlSiN-based solar-selective coating at temperatures targeted for the next generation of concentrated solar power plants.
Keywords: Concentrated solar power; high-temperature solar-selective coatings; nanolaminates; in situ analysis; ion beam analysis; STEM-EDXS imaging
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36043) publication
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Solar Energy Materials and Solar Cells 255(2023), 112305
DOI: 10.1016/j.solmat.2023.112305
Cited 5 times in Scopus
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Recovery of Release Cloud from Laser Shock-Loaded Graphite and Hydrocarbon Targets: In Search of Diamonds
Schuster, A. K.; Voigt, K.; Klemmed, B.; Hartley, N. J.; Lütgert, B. J.; Bähtz, C.; Benad, A.; Brabetz, C.; Cowan, T.; Doeppner, T.; Erb, D.; Eychmueller, A.; Facsko, S.; Falcone, R. W.; Fletcher, L. B.; Frydrych, S.; Ganzenmüller, G. C.; Gericke, D. O.; Glenzer, S. H.; Grenzer, J.; Helbig, U.; Hiermaier, S.; Hübner, R.; Laso García, A.; Lee, H. J.; Macdonald, M. J.; McBride, E. E.; Neumayer, P.; Pak, A.; Pelka, A.; Prencipe, I.; Prosvetov, A.; Rack, A.; Ravasio, A.; Redmer, R.; Reemts, D.; Rödel, M.; Schoelmerich, M.; Schumacher, D.; Tomut, M.; Turner, S. J.; Saunders, A. M.; Sun, P.; Vorberger, J.; Zettl, A.; Kraus, D.
Abstract
This work presents first insights into the dynamics of free-surface release clouds from dynamically compressed polystyrene and pyrolytic graphite at pressures up to 200 GPa, where they transform into diamond or lonsdaleite, respectively. These ejecta clouds are released into either vacuum or various types of catcher systems, and are monitored with high-speed recordings (frame rates up to 10 MHz). Molecular dynamics simulations are used to give insights to the rate of diamond preservation throughout the free expansion and the catcher impact process, highlighting the challenges of diamond retrieval. Raman spectroscopy data show graphitic signatures on a catcher plate confirming that the shock-compressed PS is transformed. First electron microscopy analyses of solid catcher plates yield an outstanding number of different spherical-like objects in the size range between ten(s) up to hundreds of nanometres, which are one type of two potential diamond candidates identified. The origin of some objects can unambiguously be assigned, while the history of others remains speculative.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 36014) publication
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Journal of Physics D: Applied Physics 56(2022), 025301
DOI: 10.1088/1361-6463/ac99e8
Cited 6 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-36014
CdSexS1−x Alloyed Nanoplatelets with Continuously Tunable Blue-Green Emission
Antanovich, A.; Yang, L.; Erwin, S. C.; Martín-García, B.; Hübner, R.; Steinbach, C.; Schwarz, D.; Gaponik, N.; Lesnyak, V.
Abstract
Cadmium chalcogenide nanoplatelets (NPLs) are established as promising materials for a wide variety of optoelectronic applications due to their properties surpassing in many aspects their counterpart nanocrystals (NCs) with other shapes. Most of these features arise from strong quantum confinement in the direction of thickness which can be tuned with precision down to one monolayer. However, atomic smoothness of their basal planes and hence the ability to change the NPL thickness only in discrete steps prevent precise tuning of absorption and photoluminescence spectra unlike in the case of quantum dots. Preparation of alloyed NCs provides a potential solution to this problem, but it is complicated by the different reactivities of chalcogenide sources, which becomes even more restrictive in the case of NPLs because they are more sensitive to alterations of reaction conditions. In this work, we overcome this obstacle by employing highly reactive stearoyl sulfide and selenide as chalcogen sources, which enable straightforward variation of the NPL composition and thickness by changing the ratio of chalcogen precursors and reaction temperature, respectively. Alloyed CdSexS1−x NPLs
obtained exhibit tunable absorption and photoluminescence bands covering the blue-green region from 380 to 520 nm with bright band-edge emission and quantum yields of ∼30−50% due to their relatively small lateral size enabled by a much finer control of the lateral growth.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 35829) publication
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Chemistry of Materials 34(2022), 10361-10372
DOI: 10.1021/acs.chemmater.2c01920
Cited 8 times in Scopus
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Formation of vertical SnSe/SnSe2 p-n heterojunction by NH3 plasma-induced phase transformation
Li, Y.; Duan, J.; Berencen, Y.; Hübner, R.; Tsai, H.-S.; Kuo, C.-N.; Chin-Shan, L.; Helm, M.; Zhou, S.; Prucnal, S.
Abstract
Layered van der Waals crystals host unique properties making them attractive for applications in nanoelectronics, optoelectronics, and sensing. The integration of two-dimensional materials with complementary metal-oxide-semiconductor (CMOS) technology requires controllable n- and p-type doping. In this work, we demonstrate the fabrication of vertical p-n heterojunctions made of p-type tin monoselenide (SnSe) and n-type tin diselenide (SnSe2). The p-n heterojunction is created in a single flake by the NH3-plasma-assisted phase transformation from SnSe2 to SnSe. We show that the transformation rate and crystal quality strongly depend on the plasma parameters like plasma power, temperature, partial pressure, NH3 flow, and duration of plasma treatment. With optimal plasma parameters, the full transformation of SnSe2 flakes to SnSe is achieved within a few seconds. The crystal quality and the topography of the fabricated SnSe-SnSe2 heterostructures are investigated using micro-Raman spectroscopy and cross-sectional transmission electron microscopy. The formation of a p-n junction is verified by current-voltage measurements.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 35576) publication
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Nanoscale Advances 5(2023), 443-449
Online First (2022) DOI: 10.1039/D2NA00434H
Cited 9 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-35576
Robust spin injection via thermal magnon pumping in antiferromagnet/ferromagnet hybrid systems
Rodriguez, R.; Regmi, S.; Zhang, H.; Yuan, W.; Makushko, P.; Montoya, E. A.; Veremchuk, I.; Hübner, R.; Makarov, D.; Shi, J.; Cheng, R.; Barsukov, I.
Abstract
Robust spin injection and detection in antiferromagnetic thin films is a prerequisite for the exploration
of antiferromagnetic spin dynamics and the development of nanoscale antiferromagnet-based spintronic applications.
Previous studies have shown spin injection and detection in antiferromagnet/nonmagnetic metal
bilayers; however, spin injection in these systems has been found effective at cryogenic temperatures only.
Here, we experimentally demonstrate sizable interfacial spin transport in a hybrid antiferromagnet/ferromagnet
system, consisting of Cr2O3 and permalloy, which remains robust up to the room temperature. We examine our
experimental data within a spin diffusion model and find evidence for the important role of interfacial magnon
pumping in the signal generation. The results bridge spin-orbitronic phenomena of ferromagnetic metals with
antiferromagnetic spintronics and demonstrate an advancement toward antiferromagnetic spin-torque devices.
Keywords: antiferromagnetic spintronics; Cr2O3 thin films; spin injection
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 35561) publication
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Physical Review Research 4(2022), 033139
DOI: 10.1103/PhysRevResearch.4.033139
Cited 7 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-35561
Seed-Mediated Synthesis of Photoluminescent Cu−Zn−In−S Nanoplatelets
Bora, A.; Prudnikau, A.; Fu, N.; Hübner, R.; Borchert, K. B. L.; Schwarz, D.; Gaponik, N.; Lesnyak, V.
Abstract
Ternary and quaternary colloidal nanocrystals (NCs) based on I−III−VI group semiconductors are promising low-toxic luminescent materials attracting huge interest as alternatives to cadmium- and lead-chalcogenide-based NCs. Despite significant progress in the synthesis of three-dimensionally confined quantum dots based on I−III−VI semiconductors with intensive photoluminescence (PL) in a broad spectral range, all attempts to prepare one-dimensionally confined nanoplatelets (NPLs) or nanosheets have resulted in rather nonemitting two-dimensional (2D) NCs. Since 2D NCs of the II−VI group exhibit unique anisotropic optical properties, exploring synthetic strategies to obtain 2D I−III−VI-based NPLs might also reveal interesting optical and electronic features. In this work, we demonstrate the synthesis of luminescent In-rich Cu−Zn−In−S (CZIS) NPLs using a one-pot approach. The synthesis includes the formation of
Cu−In−S NPLs from In2S3 seeds, followed by the incorporation of zinc to form quaternary NPLs with improved stability and optical properties. The synthetic strategy implemented results in the formation of ∼1 nm thick NPLs with lateral sizes of ∼30 × 10 nm2 and a tetragonal crystal structure. As-synthesized NPLs are stable at ambient conditions and demonstrate PL in the range of 700−800 nm with a large Stokes shift. An additional shell of ZnS grown on CZIS NPLs resulted in the enhancement of their PL quantum yield reaching 29%.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 35326) publication
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Chemistry of Materials 34(2022), 9251-9260
DOI: 10.1021/acs.chemmater.2c02500
Cited 10 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-35326
CMOS compatible manufacturing of a hybrid SET-FET circuit
Del Moral, A.; Amat, E.; Engelmann, H.-J.; Pourteau, M.-L.; Rademaker, G.; Quirion, D.; Torres-Herrero, N.; Rommel, M.; Heinig, K.-H.; von Borany, J.; Tiron, R.; Bausells, J.; Perez-Murano, F.
Abstract
This study analyzes the CMOS compatibility in the manufacturing of a hybrid SET-FET circuit. The fundamental element towards an operating SET at room temperature is a vertical nanopillar with embedded Si nanodot generated by ion-beam irradiation. The integration process from nanopillars to contacted SETs is validated by structural characterization. Then, the monolithic fabrication of planar FETs co-integrated with vertical SETs is presented, and its compatibility with standard CMOS technology is demonstrated. The work includes process optimization, pillar integrity validation, electrical characterization and simulation taking into account parasitic elements. The FET fabrication process is adapted to meet the requirements of the pre-fabricated nanopillars. Overall, this work establishes the groundwork for the realization of a hybrid SET-FET circuit operating at room temperature.
Keywords: CMOS; MOSFET; vertical nanopillar; single electron transistor; hybrid circuit
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 35323) publication
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Semiconductor Science and Technology 37(2022), 125014-125023
DOI: 10.1088/1361-6641/ac9f61
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-35323
Tuning Iron-Oxygen Covalency in Perovskite Oxides for Efficient Electrochemical Sensing
Gao, C.; Lu, Y.; Wang, Y.; Wang, C.; Hübner, R.; Li, Y.; Zhan, J.; Zhao, M.; Cai, B.
Abstract
Transition metal oxides have been extensively explored as novel catalysts for designing electrochemical sensors, but the underlying structure-activity relationship remains poorly understood. Herein, we explore a diverse chemical range of La1-xSrxFeO3 perovskite oxides by evaluating their electrochemical sensing activity toward heavy metals and by determining their electronic structures using density functional theory. We find that tuning perovskite chemistry plays an important role in determining the electrochemical activities and sensitivities, as well as the valence states of Fe. By combining experimental and theoretical analyses, a linear relationship between the Fe−O covalency and the electrochemical activity and sensitivity has been obtained, where LaFeO3 exhibits the highest activity of 109 mA cmoxide
-2.Thus, the Fe−O covalency is proposed as a rational activity descriptor for the electrochemical sensing of heavy metals. A novel solid-state gelation method was further developed for the fabrication of perovskite oxide aerogels, based on which a highly efficient electrochemical sensor was constructed with a high sensitivity of 87.06 μM μA-1 and a low detection limit of 1.7 nM. This work unlocks an effective parameter, that is, Fe−O covalency, for rationally designing Fe-based oxides and deepening the understanding of fundamental parameters to develop highly efficient sensing platforms.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 35301) publication
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Journal of Physical Chemistry C 126(2022), 17618-17626
DOI: 10.1021/acs.jpcc.2c06109
Cited 2 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-35301
Plasmonic Nanoparticles Embedded in Nanomembrane Microcavity for Flexible Optical Tuning
Pang, C.; Li, R.; Dong, H.; Saggau, C. N.; Kern, F. L.; Potapov, P.; Schultz, J.; Lubk, A.; Hübner, R.; Kentsch, U.; Zhou, S.; Helm, M.; Chen, F.; Ma, L.; Schmidt, O. G.
Abstract
The combination of plasmonic nanoparticles and optical microcavities has attracted broad interest for both fundamental and applied studies. However, the conventional scheme of plasmonic nanoparticles being located at microcavity outer surfaces suffers from serious problems such as significant radiative/scattering losses and chemical/mechanical instabilities. Here, silver nanoparticles (NPs) and dispersed ions embedded in nanomembrane-formed whispering-gallery-mode (WGM) microtube cavities are prepared by ion implantations as compact and stable optoplasmonic microcavities. Upon low ion fluence implantation, dispersed silver ions are generated in the tube cavity wall, leading to a redshift of the WGM resonant cavity modes due to the increased refractive index. The silver ions start to aggregate into plasmonic NPs in the cavity wall when increasing implantation ion fluences. The competition and transition between redshift induced by the refractive index increase and blueshift induced by the formation of plasmonic NPs are investigated. Moreover, quality factor enhancement of the WGM modes is observed owing to the improved light confinement caused by the presence of NPs. This work demonstrates a convenient approach for the fabrication of stable optoplasmonic microcavities and fine tuning of resonant modes, indicating wide applications such as wavelength selective tuning and enhanced light–matter interactions.
Keywords: ion implantation; microtube cavity; nanomembrane; plasmonic nanoparticles; resonant mode tuning
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 35020) publication
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Advanced Optical Materials 10(2022)21, 2200765
DOI: 10.1002/adom.202200765
ISSN: 2195-1071
Cited 2 times in Scopus
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Aliovalent Ta-Doping-Engineered Oxygen Vacancy Configurations for Ultralow-Voltage Resistive Memory Devices: A DFT-Supported Experimental Study
Barman, A.; Das, D.; Deshmukh, S.; Sarkar, P. K.; Banerjee, D.; Hübner, R.; Gupta, M.; Saini, C. P.; Kumar, S.; Johari, P.; Dhar, S.; Kanjilal, A.
Abstract
Alteration of transport properties of any material, especially metal oxides, by doping suitable impurities is not straightforward as it may introduce multiple defects like oxygen vacancies (Vo) in the system. It plays a decisive role in controlling the resistive switching (RS) performance of metal oxide-based memory devices. Therefore, a judicious choice of dopants and their atomic concentrations is crucial for achieving an optimum Vo configuration. Here, we show that the rational designing of RS memory devices with cationic dopants (Ta), in particular, Au/Ti1−xTaxO2−δ/Pt devices, is promising for the upcoming non-volatile memory technology. Indeed, a current window of ∼104 is realized at an ultralow voltage as low as 0.25 V with significant retention (∼104 s) and endurance (∼105 cycles) of the device by considering 1.11 at % Ta doping. The obtained device parameters are compared with those in the available literature to establish its excellent performance. Furthermore, using detailed experimental analyses and density functional theory (DFT)-based first-principles calculations, we comprehend that the meticulous presence of Vo configurations and the columnar-like dendritic structures is crucial for achieving ultralow-voltage bipolar RS characteristics. In fact, the dopant-mediated Vo interactions are found to be responsible for the enhancement in local current conduction, as evidenced from the DFT-simulated electron localization function plots, and these, in turn, augment the device performance. Overall, the present study on cationic-dopant-controlled defect engineering could pave a neoteric direction for future energy-efficient oxide memristors.
Keywords: resistive memory; vacancy engineering; ultralow-voltage switching; conducting filaments; first-principles calculations
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 35000) publication
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ACS Applied Materials and Interfaces 14(2022), 34822-34834
DOI: 10.1021/acsami.2c05089
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-35000
CO2 Electroreduction on Unsupported PdPt Aerogels: Effects of Alloying and Surface Composition on Product Selectivity
Diercks, J. S.; Georgi, M.; Herranz, J.; Diklić, N.; Chauhan, P.; Clark, A. H.; Hübner, R.; Faisnel, A.; Chen, Q.; Nachtegaal, M.; Eychmüller, A.; Schmidt, T. J.
Abstract
Due to its unique ability to reduce carbon dioxide (CO2) into CO or formate at high versus low overpotentials, respectively, palladium is a promising catalyst for the electrochemical CO2-reduction reaction (CO2RR). Further improvements aim at increasing its activity and selectivity toward either of these value-added species, while reducing the amount of hydrogen produced as a side product. With this motivation, in this work, we synthesized a range of unsupported, bimetallic PdPt aerogels and pure Pt or Pd aerogels and extensively characterized them using various microscopic and spectroscopic techniques. These revealed that the aerogels’ porous web consists of homogenous alloys of Pt and Pd, with palladium and platinum being present on their surface for all compositions. The subsequent determination of these aeorgels’ CO2RR performance unveiled that the high activity of these Pt surface atoms toward hydrogen evolution causes all PdPt alloys to favor this reaction over CO2 reduction. In the case of the pure Pd aerogel, although, its unsupported nature leads to a suppression of H2 evolution and a concomitant increase in the selectivity toward CO when compared to a commercial, carbon-supported Pd-nanoparticle catalyst.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34959) publication
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ACS Applied Energy Materials 5(2022), 8460-8471
DOI: 10.1021/acsaem.2c00987
Cited 21 times in Scopus
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Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344T
Hilpmann, S.; Roßberg, A.; Steudtner, R.; Drobot, B.; Hübner, R.; Bok, F.; Prieur, D.; Bauters, S.; Kvashnina, K.; Stumpf, T.; Cherkouk, A.
Abstract
Microbial U(VI) reduction influences the uranium mobility in contaminated subsurface environments and can affect the disposal of high-level radioactive waste by transform-ing the water-soluble U(VI) to less mobile U(IV). The reduction of U(VI) by the sulfate-reducing bacterium Desulfosporosinus hippei DSM 8344T, a close phylogenetic relative to naturally occurring microorganism present in clay rock and bentonite, was investigat-ed. D. hippei DSM 8344T showed a relatively fast removal of uranium from the superna-tants in artificial Opalinus Clay pore water. Combined speciation calculations and lumi-nescence spectroscopic investigations showed the dependence of U(VI) reduction on the initial U(VI) species. Scanning transmission electron microscopy coupled with ener-gy-dispersive X-ray spectroscopy showed uranium-containing aggregates on the cell surface and the formation of membrane vesicles. By combining different spectroscopic techniques, including UV/Vis spectroscopy, as well as uranium M4-edge X-ray absorp-tion near-edge structure (XANES) recorded in high-energy-resolution fluorescence-detection (HERFD) mode and extended X-ray absorption fine structure (EXAFS) analy-sis, the partial reduction of U(VI) could be verified, whereby the formed U(IV) product has an unknown structure. Furthermore, the U M4 HERFD-XANES showed the presence of U(V) during the process, suggesting a single-electron transfer mechanism for the microbial U(VI) reduction by sulfate reducers. These findings offer new insights into the U(VI) reduction by sulfate-reducing bacteria and contribute to a comprehensive safety concept for a repository for high-level radioactive waste.
Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Opalinus Clay pore water; Pentavalent uranium; Membrane vesicles
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Data publication: Presence of uranium(V) during uranium(VI) reduction by …
ROBIS: 34974 HZDR-primary research data are used by this (Id 34911) publication
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Science of the Total Environment 875(2023), 162593
DOI: 10.1016/j.scitotenv.2023.162593
Cited 8 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-34911
Controllable electrostatic manipulation of structure building blocks in noble metal aerogels
Wei, W.; Hübner, R.; Georgi, M.; Wang, C.; Wu, X.; Eychmüller, A.
Abstract
The important role of structure homogeneity in three-dimensional network nanostructures serving as noble metal aerogels (NMAs) has attracted extensive attention in the field of electrochemistry in the last two decades, whereas a comprehensive study of tailoring skeleton units and element distributions in NMAs is still lacking. Herein, a new modulation strategy to easily prepare multiscale NMAs with tunable composition is developed by utilizing the electrostatic interaction between oppositely charged colloidal metal nanoparticles. The modulation rule of the chemical distribution in bimetallic aerogels leads to the construction of the as-tailored double skeleton aerogels for the first time. Considering their specific structures, the intrinsic and exceptional catalytic and electrocatalytic performances of NMAs were investigated. This study optimizes the structure homogeneity of noble metal aerogels by investigating nanoparticle–ligand interactions and provides further proof of their exceptional electrocatalytic
capabilities.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34871) publication
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Materials Advances 3(2022), 5760-5771
DOI: 10.1039/d2ma00213b
Cited 7 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34871
Homogenization and short-range chemical ordering of Co-Pt alloys driven by the grain boundary migration mechanism
Pedan, R.; Makushko, P.; Dubikovskyi, O.; Bodnaruk, A.; Burmak, A.; Sidorenko, S.; Voloshko, S.; Kalita, V.; Hübner, R.; Makarov, D.; Vladymyrskyi, I.
Abstract
Binary magnetic alloys like Co-Pt are relevant for applications as components of magnetic exchange coupled composites. Numerous approaches exist to tune the coercive field of Co-Pt alloys primarily relying on hightemperature processing aiming to realize chemically long-range ordered phases. The peculiarity of Co-Pt is that large coercive field and magnetic anisotropy can be achieved even in chemically disordered alloys relying on short-range order. Here, we study alloying of Co-Pt from bilayers of Pt(14 nm) Co(13 nm) at temperatures up to 550 degС, where bulk diffusion processes are suppressed and the dominant diffusion mechanism is grain boundary migration. We demonstrate that grain boundary diffusion mechanism can lead to the realization of a homogeneous yet chemically disordered Co56Pt44 alloy at temperatures of 500 degС and higher. A pronounced increase of the coercive field for samples processed at temperatures higher than 400 degС is attributed to short-range ordering. With this work, we pinpoint the grain boundary diffusion as the mechanism responsible not only for the homogenization of binary alloy films but also as a driving force for the realization of short-range order in Co-Pt. Our results motivate further research on grain boundary diffusion as a mechanism to realize chemically long-range ordered phases in Co-Pt alloys.
Keywords: grain boundary diffusion; magnetic thin films; short-range chemical order; Co-Pt alloy
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34870) publication
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Journal of Physics D: Applied Physics 55(2022), 405004
DOI: 10.1088/1361-6463/ac8204
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34870
Pickering interfacial catalysts for asymmetric organocatalysis
Sun, Z.; Jurica, J.; Hübner, R.; Wu, C.
Abstract
Proline-catalyzed aldol reactions have been developed as an important toolbox for the synthesis of valuable chiral intermediates, giving birth to asymmetric organocatalysis. Despite progress, their current applications are generally performed in highly polar solvents that are either difficult to remove or with low substrate/product solubility. In addition, prolines are often used as homogeneous organocatalysts in these solvents, thus, the recycling of catalyst for reuse is also challenging. To solve these problems, we develop a proline-based Pickering emulsion for asymmetric aldol reactions with high reactivity and selectivity. The emulsion was stabilized by proline-functionalized silica nanoparticles that are not only highly active in the presence of water but also easily recycled after the operation. Interestingly, their high stereoselectivity was not compromised after multiple reuse, i.e., >86 ee (enantiomeric excess) in the first and second use. With this demonstration, we prove the concept that efficient and selective aldol reactions are enabled by proline-based Pickering emulsions, which is a great and continuous contribution to the field of asymmetric organocatalysis.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34869) publication
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Catalysis Science & Technology 12(2022), 4811-4816
DOI: 10.1039/d2cy00516f
Cited 3 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34869
Artificially sporulated Escherichia coli cells as a robust cell factory for interfacial biocatalysis
Sun, Z.; Hübner, R.; Li, J.; Wu, C.
Abstract
The natural bacterial spores have inspired the development of artificial spores, through coating cells with protective materials, for durable whole-cell catalysis. Despite attractiveness, artificial spores developed to date are generally limited to a few microorganisms with their natural endogenous enzymes, and they have never been explored as a generic platform for widespread synthesis. Here, we report a general approach to designing artificial spores based on Escherichia coli cells with recombinant enzymes. The artificial spores are simply prepared by coating cells with polydopamine, which can withstand UV radiation, heating and organic solvents. Additionally, the protective coating enables living cells to stabilize aqueous-organic emulsions for efficient interfacial biocatalysis ranging from single reactions to multienzyme cascades. Furthermore, the interfacial system can be easily expanded to chemoenzymatic synthesis by combining artificial spores with metal catalysts. Therefore, this artificial-spore-based platform technology is envisioned to lay the foundation for nextgeneration cell factory engineering.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34868) publication
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Nature Communications 13(2022), 3142
DOI: 10.1038/s41467-022-30915-2
Cited 35 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34868
CMOS-compatible manufacturability of sub-15 nm Si/SiO2/Si nanopillars containing single Si nanodots for single electron transistor applications
Borany, J.; Engelmann, H.-J.; Heinig, K.-H.; Amat, E.; Hlawacek, G.; Klüpfel, F.; Hübner, R.; Möller, W.; Pourteau, M.-L.; Rademaker, G.; Rommel, M.; Baier, L.; Pichler, P.; Perez-Murano, F.; Tiron, R.
Abstract
This study addresses the complementary metal-oxide-semiconductor-compatible fabrication of vertically stacked Si/SiO2/Si nanopillars (NPs) with embedded Si nanodots (NDs) as key functional elements of a quantum-dot-based, gate-all-around single-electron transistor (SET) operating at room temperature. The main geometrical parameters of the NPs and NDs were deduced from SET device simulations using the nextnano++ program package. The basic concept for single silicon ND formation within a confined oxide volume was deduced from Monte-Carlo simulations of ion-beam mixing and SiOx phase separation. A process flow was developed and experimentally implemented by combining bottom-up (Si ND self-assembly) and top-down (ion-beam mixing, electron-beam lithography, reactive ion etching) technologies, fully satisfying process requirements of future 3D device architectures. The theoretically predicted self-assembly of a single Si ND via phase separation within a confined SiOx disc of < 500 nm³ volume was experimentally validated. This work describes in detail the optimization of conditions required for NP/ND formation, such as the oxide thickness, energy and fluence of ion-beam mixing, thermal budget for phase separation and parameters of reactive ion beam etching. Low-temperature plasma oxidation was used to further reduce NP diameter and for gate oxide fabrication whilst preserving the pre-existing NDs. The influence of critical dimension variability on the SET functionality and options to reduce such deviations are discussed. We finally demonstrate the reliable formation of Si quantum dots with diameters of less than 3 nm in the oxide layer of a stacked Si/SiO2/Si NP of 10 nm diameter, with tunnelling distances of about 1 nm between the Si ND and the neighboured Si regions forming drain and source of the SET.
Keywords: CMOS; single-electron transistor; nanostructure fabrication; nanpillars; silicon nanodot; self-organization; ion-beam mixing
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34842) publication
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Data publication: CMOS-compatible manufacturability of sub-15 nm Si/SiO2/Si …
ROBIS: 34906 HZDR-primary research data are used by this (Id 34842) publication
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Semiconductor Science and Technology 38(2023)5, 055011
DOI: 10.1088/1361-6641/acbe5d
Permalink: https://www.hzdr.de/publications/Publ-34842
Flexomagnetism and vertically graded Néel temperature of antiferromagnetic Cr2O3 thin films
Makushko, P.; Kosub, T.; Pylypovskyi, O.; Hedrich, N.; Li, J.; Pashkin, O.; Avdoshenko, S.; Hübner, R.; Ganss, F.; Liedke, M. O.; Butterling, M.; Wagner, A.; Wagner, K.; Shields, B. J.; Lehmann, P.; Veremchuk, I.; Faßbender, J.; Maletinsky, P.; Makarov, D.
Abstract
Antiferromagnetic insulators are a prospective material science platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A magnetomechanical coupling in antiferromagnets offers vast advantages in the control and manipulation of the primary order parameter yet remains largely unexplored both fundamentally and technologically. Here, we discover a new member in the family of flexoeffects in thin films of technologically relevant antiferromagnetic Cr2O3. We demonstrate that a gradient of mechanical strain can impact the magnetic phase transition resulting in the distribution of the N ́eel temperature along the thickness of a 50-nm-thick film and induces a sizable flexomagnetic coefficient of about 15 μb/nm2 originating from the inhomogeneous reduction of the antiferromagnetic order parameter. The antiferromagnetic ordering in inhomogeneously strained thin films of Cr2O3 can persist up to 100◦ C, rendering Cr2O3 relevant for industrial electronics applications. The presence of a strain gradient in thin films of Cr2O3 may therefore allow for the realization of reconfigurable antiferromagnetic racetracks, magnonic waveguides and magnon crystals. The presence of a strain gradient in ultrathin films of Cr2O3 enables new fundamental research directions on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with continuously graded parameters.
Keywords: antiferromagnetism; flexomagnetism; Cr2O3; Neel temperature; NV magnetometry; magnetotransport
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
- P-ELBE
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34673) publication
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Nature Communications 13(2022), 6745
DOI: 10.1038/s41467-022-34233-5
Cited 36 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34673
Expanding the Range: AuCu Metal Aerogels from H2O and EtOH
Georgi, M.; Kresse, J.; Hiekel, K.; Hübner, R.; Eychmüller, A.
Abstract
Due to their self-supporting and nanoparticulate structure, metal aerogels have emerged as excellent electrocatalysts, especially in the light of the shift to renewable energy cycles. While a large number of synthesis parameters have already been studied in depth, only superficial attention has been paid to the solvent. In order to investigate the influence of this parameter with respect to the gelation time, crystallinity, morphology, or porosity of metal gels, AuxCuy aerogels were prepared in water and ethanol. It was shown that although gelation in water leads to highly porous gels (60 m2g-1), a CuO phase forms during this process. The undesired oxide could be selectively removed using a post-washing step with formic acid. In contrast, the solvent change to EtOH led to a halving of the gelation time and the suppression of Cu oxidation. Thus, pure Cu aerogels were synthesized in addition to various bimetallic Au3X (X = Ni, Fe, Co) gels. The faster gelation, caused by the lower permittivity of EtOH, led to the formation of thicker gel strands, which resulted in a lower porosity of the AuxCuy aerogels. The advantage given by the solvent choice simplifies the preparation of metal aerogels and provides deeper knowledge about their gelation.
Keywords: metal; aerogel; gold; copper; ethanol; water; solvent; bimetallic; porous; one-step
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34591) publication
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Catalysts 12(2022)4, 441
DOI: 10.3390/catal12040441
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34591
Speciation and spatial distribution of Eu(III) in fungal mycelium
Günther, A.; Wollenberg, A.; Vogel, M.; Drobot, B.; Steudtner, R.; Freitag, L.; Hübner, R.; Stumpf, T.; Raff, J.
Abstract
Europium, as an easy-to-study analog of the trivalent actinides, is of particular importance for studying the behavior of lanthanides and actinides in the environment. Since different soil organisms can influence the migration behavior of these elements, a detailed knowledge of these interaction mechanisms is important. The aim of this study was to investigate the interaction of mycelia of selected wood-inhabiting (S. commune, P. ostreatus, L. tigrinus) and soil-inhabiting fungi (L. naucinus) with Eu(III). In addition to determining the Eu(III) complexes in the sorption solution, the formed Eu(III) fungal species were characterized using scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, chemical microscopy in combination with the time-resolved laser-induced fluorescence spectroscopy. Our data show that S. commune exhibited significantly higher Eu(III) binding capacity in comparison to the other fungi. Depending on fungal strain, the metal was immobilized on the cell surface, in the cell membranes, and within the membranes of various organelles, or in the cytoplasm in some cases. During the bioassociation process two different Eu(III) fungal species were formed in all investigated fungal strain. The phosphate groups of organic ligands were identified as being important functional groups to bind Eu(III) and thus immobilize the metal in the fungal matrix. The information obtained contributes to a better understanding of the role of fungi in migration, removal or retention mechanisms of rare earth elements and trivalent actinides in the environment.
Keywords: Fungi; Europium; Speciation; Scanning transmission electron microscopy (STEM); Chemical microscopy; Time-resolved laser-induced fluorescence spectroscopy (TRLFS)
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Science of the Total Environment 851(2022), 158160
DOI: 10.1016/j.scitotenv.2022.158160
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34580
Band-gap and strain engineering in GeSn alloys using post-growth pulsed laser melting
Steuer, O.; Schwarz, D.; Oehme, M.; Schulze, J.; Mączko, H.; Kudrawiec, R.; Fischer, I. A.; Heller, R.; Hübner, R.; Khan, M. M.; Georgiev, Y.; Zhou, S.; Helm, M.; Prucnal, S.
Abstract
Alloying Ge with Sn enables effective band-gap engineering and improves significantly the charge carrier mobility. The pseudomorphic growth of Ge1-xSnx on Ge causes in-plane compressive strain, which degrades the superior properties of the Ge1-xSnx alloys. Therefore, efficient strain engineering is required. In this article, we present strain and band-gap engineering in GeSn alloys grown on Ge a virtual substrate using post-growth nanosecond pulsed laser melting (PLM). Micro-Raman and X-ray diffraction show that the initial in-plane compressive strain is removed. Moreover, for PLM energy densities higher than 0.5 J cm-2, the Ge0.89Sn0.11 layer becomes tensile strained. Simultaneously, as revealed by Rutherford Backscattering spectrometry, cross-sectional transmission electron microscopy investigations and X-ray diffraction the crystalline quality and Sn-distribution in PLM-treated Ge0.89Sn0.11 layers are only slightly affected. Additionally, the change of the band structure after PLM is also confirmed by low-temperature photoreflectance measurements. The presented results prove that post-growth ns-range PLM is an effective way for band-gap and strain engineering in highly-mismatched alloys.
Keywords: Germanium Tin; band-gap engineering; GeSn; pseudomorphic growth; pulsed laser melting; GeSn alloys; molecular-beam epitaxy; Ge1-xSnx
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34559) publication
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Journal of Physics: Condensed Matter 35(2023)5, 055302
Online First (2022) DOI: 10.1088/1361-648X/aca3ea
Cited 8 times in Scopus -
Vortrag (Konferenzbeitrag)
Band-gap and strain engineering in GeSn alloys using post-growth pulsed laser melting, 05.-09.09.2022, Regensburg, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-34559
Localization and chemical speciation of europium(III) in Brassica napus plants
Jessat, J.; John, W.; Moll, H.; Vogel, M.; Steudtner, R.; Drobot, B.; Hübner, R.; Stumpf, T.; Sachs, S.
Abstract
For the reliable safety assessment of repositories of highly radioactive waste, further development of the modelling of radionuclide migration and transfer in the environment is necessary, which requires a deeper process understanding at the molecular level. Eu(III) is a non-radioactive analogue for trivalent actinides, which contribute heavily to radiotoxicity in a repository. For in-depth study of the interaction of plants with trivalent f elements, we investigated the uptake, speciation, and localization of Eu(III) in Brassica napus plants at two concentrations, 30 and 200 µM, as a function of the incubation time up to 72 h. Eu(III) was used as luminescence probe for combined microscopy and chemical speciation analyses of it in Brassica napus plants. The localization of bioassociated Eu(III) in plant parts was explored by spatially resolved chemical microscopy. Three Eu(III) species were identified in the root tissue. Moreover, different luminescence spectroscopic techniques were applied for an improved Eu(III) species determination in solution. In addition, transmission electron microscopy combined with energy-dispersive X-ray spectroscopy was used to localize Eu(III) in the plant tissue, showing Eu-containing aggregates. By using this multi-method setup, a profound knowledge on the behavior of Eu(III) within plants and changes in its speciation could be obtained, showing that different Eu(III) species occur simultaneously within the root tissue and in solution.
Keywords: lanthanides; plants; laser spectroscopy; speciation; chemical microscopy; localization
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Ecotoxicology and Environmental Safety 254(2023), 114741
DOI: 10.1016/j.ecoenv.2023.114741
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34537
Peptidoglycan as major binding motif for Uranium bioassociation on Magnetospirillum magneticum AMB-1 in contaminated waters
Krawczyk-Bärsch, E.; Ramtke, J.; Drobot, B.; Müller, K.; Steudtner, R.; Kluge, S.; Hübner, R.; Raff, J.
Abstract
The mining and industrial use of heavy metals lead to locally high heavy metal contamination with serious consequences for the environment and local population. The high potential of biological remediation processes, in particular, the use of magnetotactic bacteria of heavy metal and radionuclide-contaminated waters has recently been discussed. Yet, the molecular reactions involved in the uptake of radionuclides, especially U, by these bacteria are unknown. The present work is a multidisciplinary approach combining wet chemistry, microscopy, and spectroscopy methods. Our findings suggest that the cell wall plays a prominent role in the bioassociation of U(VI). In time-dependent bioassociation studies, up to 95 % of the initial U(VI) was removed from the suspension within the first hours by Magnetospirillum magneticum AMB-1. PARAFAC analysis of TRLFS data highlights that peptidoglycan is the most important ligand involved, showing a stable immobilization of U(VI) over a wide pH range with the formation of three characteristic species. In addition, in-situ ATR FT-IR reveals the predominant binding to carboxylic functionalities, at higher pH polynuclear species seem to play an important role. This comprehensive molecular study may initiate in future new remediation strategies on effective immobilization of U in combination with the bacteria´s magnetic properties.
Keywords: Magnetotactic bacteria; Uranium; Spectroscopy; Microscopy; Bioremediation
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Journal of Hazardous Materials 437(2022), 129376
DOI: 10.1016/j.jhazmat.2022.129376
Cited 5 times in Scopus
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Epitaxial lateral overgrowth of tin spheres driven and directly observed by helium ion microscopy
Klingner, N.; Heinig, K.-H.; Tucholski, D.; Möller, W.; Hübner, R.; Bischoff, L.; Hlawacek, G.; Facsko, S.
Abstract
Enhanced interstitial diffusion in tin is a phenomenon often observed during ion-beam irradiation and in lead-free solders. For the latter, this
not very well understood, strain-driven mechanism results in the growth of whiskers, which can lead to unwanted shorts in electronic designs. In ion-beam physics, this phenomenon is often observed as a result of the enhanced formation of Frenkel pairs in the energetic collision cascade. Here, we show how epitaxial growth of tin extrusions on tin-oxide-covered tin spheres can be induced and simultaneously observed by implanting helium using a helium ion microscope. Calculations of collision cascades based on the binary collision approximation and 3D-lattice-kinetic Monte Carlo simulations show that the implanted helium will occupy vacancy sites, leading to a tin interstitial excess. Sputtering and phase separation of the tin oxide skin, which is impermeable for tin atoms, create holes and will allow the epitaxial overgrowth to start. Simultaneously, helium accumulates inside the irradiated spheres. Fitting the simulations to the experimentally observed morphology allows us to estimate the tin to tin-oxide interface energy to be 1.98 J m−2 . Our approach allows the targeted initiation and in situ observation of interstitial diffusion-driven effects to improve the understanding of the tin-whisker growth mechanism observed in lead-free solders.
Keywords: helium ion microscope; tin whisker growth; defect kinetics
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34525) publication
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Data publication: Epitaxial lateral overgrowth of tin spheres driven and …
ROBIS: 34526 HZDR-primary research data are used by this (Id 34525) publication
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The Journal of Physical Chemistry Letters 126(2022), 16332-16340
DOI: 10.1021/acs.jpcc.2c03707
Cited 1 times in Scopus
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Depth-Adjustable Magnetostructural Phase Transition in Fe₆₀V₄₀ Thin Films
Anwar, M. S.; Cansever, H.; Boehm, B.; Gallardo, R.; Hübner, R.; Zhou, S.; Kentsch, U.; Rauls, S.; Eggert, B.; Wende, H.; Potzger, K.; Faßbender, J.; Lenz, K.; Lindner, J.; Hellwig, O.; Bali, R.
Abstract
Phase transitions occurring within spatially confined regions can be useful for generating nanoscale material property modulations. Here we describe a magneto-structural phase transition in a binary alloy, where a structural transition from short range order (SRO) to body centered cubic (bcc) results in the formation of depth-adjustable ferromagnetic layers, which reveal application-relevant magnetic properties of high saturation magnetitzation (Ms) and low Gilbert damping (α). Here we use Fe₆₀V₄₀ binary alloy films which transform from initially Ms = 17 kA/m (SRO structure) to 747 kA/m (bcc structure) driven by atomic displacements caused by penetrating ions. Simulations show that estimated ~1 displacement per atom triggers a structural transition, forming homogeneous ferromagnetic layers. The thickness of ferromagnetic layer increases as a step-like function of the ion-fluence. Microwave excitations of the ferromagnetic/non-ferromagnetic layered system reveals an α = 0.0027 ± 0.0001. The combination of nanoscale spatial confinement, low α and high Ms provide a pathway for the rapid patterning of magnetic and microwave device elements.
Keywords: Magneto-structural correlations; Phase transitions; Magnetic thin films; Ion-irradiation; Short-range order
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34510) publication
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ACS Applied Electronic Materials 4(2022)8, 3860-3869
DOI: 10.1021/acsaelm.2c00499
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34510
Tunable metal hydroxide–organic frameworks for catalysing oxygen evolution
Yuan, S.; Peng, J.; Cai, B.; Huang, Z.; Garcia-Esparza, A. T.; Sokaras, D.; Zhang, Y.; Giordano, L.; Akkiraju, K.; Guang Zhu, Y.; Hübner, R.; Zou, X.; Román-Leshkov, Y.; Shao-Horn, Y.
Abstract
The oxygen evolution reaction is central to making chemicals and energy carriers using electrons. Combining the great tunability of enzymatic systems with known oxide-based catalysts can create breakthrough opportunities to achieve both high activity and stability. Here we report a series of metal hydroxide–organic frameworks (MHOFs) synthesized by transforming layered hydroxides into two-dimensional sheets crosslinked using aromatic carboxylate linkers. MHOFs act as a tunable catalytic platform for the oxygen evolution reaction, where the π–π interactions between adjacent stacked linkers dictate stability, while the nature of transition metals in the hydroxides modulates catalytic activity. Substituting Ni-based MHOFs with acidic cations or electron-withdrawing linkers enhances oxygen evolution reaction activity by over three orders of magnitude per metal site, with Fe substitution achieving a mass activity of 80 A gcatalyst
-1 at 0.3 V overpotential for 20 h. Density functional theory calculationscorrelate the enhanced oxygen evolution reaction activity with the MHOF-based modulation of Ni redox and the optimized binding of oxygenated intermediates.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34431) publication
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Nature Materials 21(2022), 673-680
DOI: 10.1038/s41563-022-01199-0
Cited 195 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34431
Self-Supported Three-Dimensional Quantum Dot Aerogels as a Promising Photocatalyst for CO2 Reduction
Jiang, G.; Wang, J.; Li, N.; Hübner, R.; Georgi, M.; Cai, B.; Li, Z.; Lesnyak, V.; Gaponik, N.; Eychmüller, A.
Abstract
With the merits of quantum dots (QDs) (e.g., high molar extinction coefficient, strong visible light absorption, large specific surface area, and abundant functional surface active sites) and aerogels (e.g., self-supported architectures, porous network), semiconductor QD aerogels show great prospect in photocatalytic applications. However, typical gelation methods rely on oxidative treatments of QDs. Moreover, the remaining organic ligands (e.g., mercaptoacids) are still present on the surface of gels. Both these factors inhibit the activity of such photocatalysts, hampering their widespread use.
Herein, we present a facile 3D assembly of II−VI semiconductor QDs capped with inorganic (NH4)2S ligands into aerogels using H2O as a dispersion solvent. Without any sacrificial agents, the resulting CdSe QD aerogels achieve a high CO generation rate of 15 μmol g-1 h-1, which is 12-fold higher than that of pristine-aggregated QD powders. Our work not only provides a facile strategy to fabricate QD aerogels but also offers a platform for designing advanced aerogel-based photocatalysts.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34412) publication
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Chemistry of Materials 34(2022), 2687-2695
DOI: 10.1021/acs.chemmater.1c04028
Cited 18 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34412
Mid- and far-infrared localized surface plasmon resonances in chalcogen-hyperdoped silicon
Wang, M.; Yu, Y.; Prucnal, S.; Berencén, Y.; Saif Shaikh, M.; Rebohle, L.; Khan, M. B.; Zviagin, V.; Hübner, R.; Pashkin, A.; Erbe, A.; Georgiev, Y. M.; Grundmann, M.; Helm, M.; Kirchner, R.; Zhou, S.
Abstract
Plasmonic sensing in the infrared region employs the direct interaction of the vibrational fingerprints of molecules with the plasmonic resonances, creating surface-enhanced sensing platforms that are superior to traditional spectroscopy. However, the standard noble metals used for plasmonic resonances suffer from high radiative losses as well as fabrication challenges, such as tuning the spectral resonance positions into mid- to far-infrared regions, and the compatibility issue with the existing complementary metal–oxide-semiconductor (CMOS) manufacturing platform. Here, we demonstrate the occurrence of mid-infrared localized surface plasmon resonances (LSPR) in thin Si films hyperdoped with the known deep-level impurity tellurium. We show that the mid-infrared LSPR can be further enhanced and spectrally extended to the far-infrared range by fabricating two-dimensional arrays of micrometer-sized antennas in a Te-hyperdoped Si chip. Since Te-hyperdoped Si can also work as an infrared photodetector, we believe that our results will unlock the route toward the direct integration of plasmonic sensors with the on-chip CMOS platform, greatly advancing the possibility of mass manufacturing of high-performance plasmonic sensing systems.
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- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34401) publication
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Nanoscale 14(2022), 2826-2836
DOI: 10.1039/D1NR07274A
Cited 10 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-34401
Magnetism and magnetoelectricity of textured polycrystalline bulk Cr2O3 sintered in conditions far out of equilibrium
Veremchuk, I.; Makushko, P.; Hedrich, N.; Zabila, Y.; Kosub, T.; Liedke, M. O.; Butterling, M.; Attallah, A. G.; Wagner, A.; Burkhardt, U.; Pylypovskyi, O.; Hübner, R.; Faßbender, J.; Maletinsky, P.; Makarov, D.
Abstract
Magnetoelectric antiferromagnets like Cr2O3 are attractive for the realization of energy-efficient and high-speed spin-orbitronic-based memory devices. Here, we demonstrate that fabrication of polycrystalline bulk Cr2O3 samples in conditions far out of equilibrium relying on spark plasma sintering allows to realize high-quality material with density close to that of a single crystal. The sintered sample possesses a preferential [001] texture at the surface, which can be attributed to uniaxial strain applied to the sample during the sintering process. The antiferromagnetic state of the sample and linear magnetoelectric effect are accessed all-electrically relying on the spin Hall magnetoresistance effect in the Pt electrode interfaced with Cr2O3. In line with the integral magnetometry measurements, the magnetotransport characterization reveals that the sample possesses the magnetic phase transition temperature of about 308 K, which is the same as in a single crystal. The antiferromagnetic domain pattern consists of small domains with sizes in the range of several micrometers only, which is formed due to the granular structure of the sample. The possibility to access the magnetoelectric properties of the samples relying on magnetotransport measurements indicates the potential of the polycrystalline Cr2O3 samples for prospective research in antiferromagnetic spintronics.
Keywords: magnetoelectric; antiferromagnet; Cr2O3; spark plasma sintering; magnetotransport
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- Strahlungsquelle ELBE DOI: 10.17815/jlsrf-2-58
- P-ELBE
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- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 34361) publication
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ACS Applied Electronic Materials 4(2022), 2943-2952
DOI: 10.1021/acsaelm.2c00398
Cited 8 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-34361
Defect nanostructure and its impact on magnetism of α-Cr2O3 thin films
Veremchuk, I.; Liedke, M. O.; Makushko, P.; Kosub, T.; Hedrich, N.; Pylypovskyi, O.; Ganss, F.; Butterling, M.; Hübner, R.; Attallah, A. G.; Wagner, A.; Wagner, K.; Shields, B.; Maletinsky, P.; Faßbender, J.; Makarov, D.
Abstract
Thin films of the magnetoelectric insulator α-Cr2O3 are technologically relevant for energy-efficient magnetic memory devices controlled by electric fields. In contrast to single crystals, the quality of thin Cr2O3 films is usually compromised by the presence of point defects and their agglomerations at grain boundaries, putting into question their application potential. Here, we study the impact of the defect nanostructure including sparse small-volume defects and their complexes on the magnetic properties of Cr2O3 thin films. By tuning the deposition temperature, we tailor the type, size, and relative concentration of defects, which we then analyze based on positron annihilation spectroscopy complemented with local electron microscopy studies. The structural characterization is correlated with magnetotransport measurements and nitrogen vacancy microscopy of antiferromagnetic domain patterns. Defects pin antiferromagnetic domain walls and stabilize complex multidomain states with a typical domain size in the sub-micrometer range. Despite their influence on the domain configuration, we demonstrate that neither small open-volume defects nor grain boundaries in Cr2O3 thin films affect the Néel temperature in a broad range of deposition parameters. Our results pave the way towards the realization of spin-orbitronic devices where magnetic domain patterns can be tailored based on defect nanostructures without affecting their operation temperature.
Keywords: Cr2O3 thin films; antiferromagnet; antiferromagnetic domains; magnetotransport; vacancy cluster; dislocations
Beteiligte Forschungsanlagen
- Strahlungsquelle ELBE DOI: 10.17815/jlsrf-2-58
- P-ELBE
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 34360) publication
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Small 18(2022)17, 2201228
DOI: 10.1002/smll.202201228
Cited 13 times in Scopus -
Vortrag (Konferenzbeitrag)
IEEE International Conference "Nanomaterials: Applications & Properties", 11.-16.09.2022, Krakow, Poland
Permalink: https://www.hzdr.de/publications/Publ-34360
A comprehensive study on the interaction of Eu(III) and U(VI) with plant cells (Daucus carota) in suspension
Jessat, J.; Moll, H.; John, W.; Bilke, M.-L.; Hübner, R.; Kretzschmar, J.; Steudtner, R.; Drobot, B.; Stumpf, T.; Sachs, S.
Abstract
Daucus carota suspension cells showed a high affinity towards Eu(III) and U(VI) based on a single-step bioassociation process with an equilibrium after 48 to 72 h. Cells responded with an increased metabolic activity towards heavy metal stress. Luminescence spectroscopy pointed to multiple species for both heavy metals in the culture media, providing initial hints of their interaction with cells and released metabolites. Using nuclear magnetic resonance spectroscopy, we could prove that malate, as an released metabolite in the culture medium, was found to complex with U. Luminescence spectroscopy also showed that Eu(III)-EDTA species are interacting with the cells. Furthermore, Eu(III) and U(VI) coordination is dominated by phosphate groups provided by the cells. We found that Ca ion channels of D. carota cells were involved in the uptake of U(VI), which led to a bioprecipitation of U(VI) in the vacuole of the cells, most probably as uranyl(VI) phosphates along with an intracellular sorption of U(VI) on biomembranes by lipid structures. Eu(III) could be found locally concentrated in the cell wall and in the cytoplasm with a co-localization with phosphorous and oxygen.
Keywords: actinides; lanthanides; luminescence spectroscopy; malate; mobilization
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Journal of Hazardous Materials 439(2022), 129520
DOI: 10.1016/j.jhazmat.2022.129520
Cited 7 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-34322
Extraordinary anisotropic magnetoresistance in CaMnO3/CaIrO3 heterostructures
Vagadia, M.; Sardar, S.; Tank, T.; Das, S.; Gunn, B.; Pandey, P.; Hübner, R.; Rodolakis, F.; Fabbris, G.; Choi, Y.; Haskel, D.; Frano, A.; Rana, D. S.
Abstract
The realization of fourfold anisotropic magnetoresistance (AMR) in 3d-5d heterostructures has boosted major efforts in antiferromagnetic (AFM) spintronics. However, despite the potential of incorporating strong spinorbit coupling, only small AMR signals have been detected thus far, prompting a search for mechanisms to enhance the signal. In this paper, we demonstrate an extraordinarily elevated fourfold AMR of 70% realized in CaMnO3/CaIrO3 thin film superlattices.We find that the biaxial magnetic anisotropy and the spin-flop transition in a nearly Mott insulating phase form a potent combination, each contributing one order of magnitude to the total signal. Dynamics between these phenomena capture a subtle interaction of pseudospin coupling with the lattice and external magnetic field, an emergent phenomenon creating opportunities to harness its potential in AFM spintronics.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 34027) publication
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Physical Review B 105(2022), L020402
DOI: 10.1103/PhysRevB.105.L020402
Cited 14 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-34027
Role of the metal supply pathway on silicon patterning by oblique ion beam sputtering
Redondo-Cubero, A.; Palomares, F. J.; Lorenz, K.; Rubio-Zuazo, J.; Hübner, R.; Mompéan, F. J.; García-Hernández, M.; Castro, G. R.; Vázquez, L.
Abstract
The dynamics of the pattern induced on a silicon surface by oblique incidence of a 40 keV Fe ion beam is studied. The results are compared with those obtained for two reference systems, namely a noble gas ion beam either without or with Fe co-deposition. The techniques employed include Atomic Force Microscopy, Rutherford Backscattering Spectrometry, Transmission Electron Microscopy, X-ray Photoelectron and hard X-ray photoelectron spectroscopies, as well as Superconducting Quantum Interference Device measurements. The Fe-induced pattern differs from those of both reference systems since a pattern displaying short hexagonal ordering develops, although it shares some features with them. In both Fe systems a chemical pattern, with iron silicide-rich and -poor regions, is formed upon prolonged irradiation. The metal pathway has a marked influence on the patterns’ morphological properties and on the spatial correlation between the chemical and morphological patterns. It also determines the iron silicide stoichiometry and the surface pattern magnetic properties that are better for the Feimplanted system. These results show that in ion-beam-induced silicon surface patterning with reactive metals, the metal supply pathway is critical to determine not only the morphological pattern properties, but also the chemical and magnetic ones.
Keywords: Surface nanopatterning; Ion beam sputtering; Silicon; Magnetic properties; Silicides; Iron
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 33811) publication
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Applied Surface Science 580(2022), 152267
Online First (2021) DOI: 10.1016/j.apsusc.2021.152267
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-33811
Controlled Silicidation of Silicon Nanowires using Flash Lamp Annealing
Khan, M. B.; Prucnal, S.; Ghosh, S.; Deb, D.; Hübner, R.; Pohl, D.; Rebohle, L.; Mikolajick, T.; Erbe, A.; Georgiev, Y.
Abstract
Among other new device concepts, nickel silicide (NiSix)-based Schottky barrier nanowire transistors are projected to supplement down-scaling of the complementary metal-oxide-semiconductor (CMOS) technology as its physical limits are reached. Control over the NiSix phase and its intrusions into the nanowire are essential for superior performance and down-scaling of these devices. Several works have shown control over the phase, but control over the intrusion lengths has remained a challenge. To overcome this, we report a novel millisecond-range flash-lamp-annealing (FLA)-based silicidation process. Nanowires are fabricated on silicon-on-insulator substrates using a top-down approach. Subsequently, Ni silicidation experiments are carried out using FLA. It is demonstrated that this silicidation process gives unprecedented control over the silicide intrusions. Scanning electron microscopy and high-resolution transmission electron microscopy are performed for structural characterization of the silicide. FLA temperatures are estimated with the help of simulations.
Beteiligte Forschungsanlagen
- Ionenstrahlzentrum DOI: 10.17815/jlsrf-3-159
Verknüpfte Publikationen
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 33436) publication
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Data publication: Controlled Silicidation of SiNW using FLA
ROBIS: 33452 HZDR-primary research data are used by this (Id 33436) publication
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Langmuir 37(2021)49, 14284-14291
DOI: 10.1021/acs.langmuir.1c01862
Cited 10 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-33436
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