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33403 Publications

Mineral exploration using hyperspectral remote sensing

Laakso, K.
There is no abstract associated with the talk.
Keywords: Hyperspectral, remote sensing, mineral exploration
  • Invited lecture (Conferences)
    An informal lecture to the students of Mathias Burisch (Tu Bergakademie Freiberg), associate professor., 06.02.2017, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24782
Publ.-Id: 24782


Hyperspectral applications of mineral exploration

Laakso, K.
The talk does not have an abstract.
Keywords: Hyperspectral, mineral exploration, remote sensing, drill core imaging
  • Invited lecture (Conferences)
    University of Lorraine - an informal meeting where scientific collaboration will be discussed, 24.01.2017, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-24781
Publ.-Id: 24781


Extended soft wall model with background related to features of QCD thermodynamics

Zöllner, R.; Kämpfer, B.
The soft wall model is extended to accommodate at the same time (i) approximately linear ρ meson Regge trajectories at zero temperature T, (ii) various options for the thermodynamics with reference to QCD (cross over or second-order transition or first-order transition at Tc), and (iii) the appearance of vector meson states at T≤Tc. While the vector meson masses display some modest model dependence very near to Tc, they stay below Tc to good accuracy independent of the temperature, that is nearly as at T=0, thus being very consistent with the thermo-statistical models widely employed in analyses of the hadron yields in relativistic heavy-ion collisions in a region where baryon densitiy effects can be neglected and the vacuum hadron masses are used.

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Permalink: https://www.hzdr.de/publications/Publ-24780
Publ.-Id: 24780


Fragment Molecular Orbital Calculations for Studying Lanthanide-Protein Interaction

Tsushima, S.ORC
no abstract for this talk
  • Invited lecture (Conferences)
    Institute Colloquium at Institute of Innovative Research, Tokyo Institute of Technology, 27.01.2017, Tokyo, Japan

Permalink: https://www.hzdr.de/publications/Publ-24779
Publ.-Id: 24779


Optik einmal anders

Schultheiss, H.
Erstmals konnten Forscher experimentell das Brechungsgesetz für Spinwellen direkt nachweisen.
Keywords: Magnonik, Spinwellen, Magnetisierungsdynamik
  • Physik Journal 15(2016)10, 16-17

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Permalink: https://www.hzdr.de/publications/Publ-24778
Publ.-Id: 24778


CdZnTe als Strahlungsdetektor in der therapeutischen Medizin

Weinberger, D.; Römer, K.; Lutz, B.; Fiedler, F.; Kormoll, T.
Alternativ zu Operation und Chemotherapie bei der Behandlung von Tumoren hat die Strahlentherapie einen festen Platz in der medizinischen Behandlung eingenommen. Neben der Therapie mit Röntgenstrahlung werden auch geladene Atome als Teilchenstrahl verwendet. Diese haben eine endliche Reichweite in Materie und deponieren keine schädliche Dosis dahinter. Um diesen Vorteil nutzen zu können muss die Eindringtiefe des Strahls erfasst werden. CdZnTe als Strahlungsdetektor besitzt dieses Potential.
Keywords: Strahlungsdetektor, CdZnTe-Streifendetektor, Driftstrom, Pulsformenanalyse, Tiefenkorrektur
  • Contribution to proceedings
    18. Nachwuchswissenschaftlerkonferenz ost- und mitteldeutscher Fachhochschulen, 31.05.2017, Mittweida, Deutschland
    Proceedings der 18. Nachwuchswissenschaftlerkonferenz ost- und mitteldeutscher Fachhochschulen

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Permalink: https://www.hzdr.de/publications/Publ-24777
Publ.-Id: 24777


Level-Of-Detail Strategie zur Vereinfachung komplexer Untergrundmodelle - Gifhorner Trog

Menzel, P.; Götze, H.-J.; Schmidt, S.
In dieser Präsentation werden Verfahren gezeigt, um triangulierte 3D-Untergrundmodelle für die Berechnung ihres „full tensor gravity“-Effektes zu optimieren. Es handelt sich dabei um zwei etablierte Algorithmen aus der Computergrafik zur Vereinfachung von triangulierten Flächen, sowie um ein drittes, an die Erfordernisse der Potentialverfahren angepasstes, Verfahren. Alle drei Algorithmen erzeugen eine Vereinfachungshierarchie für die initiale 3D-Geometrie. Diese „Level-of-Detail“-Hierarchien erlauben es, verschiedene Modell-auflösungen sukzessive ineinander zu überführen. Ein explizites Vorhalten der vereinfachten Geometrieversionen ist aus diesem Grund nicht notwendig.
Die drei verwendeten „Mesh-Simplification“-Ansätze werden auf ein synthetisches 3D-Modell und auf das triangulierte Untergrundmodell zweier realer Salzstöcke angewendet. Die erzeugten vereinfachten Geometrieversionen werden für ihre Verwendbarkeit zur Berechnung des Effektes in den Komponenten der Schwere und des Schweregradienten-tensors evaluiert. Es wird gezeigt, dass die Ergebnisse aller drei Methoden grundsätzliche für eine Berechnung des „full tensor gravity“-Effektes verwendet werden können. Die Ergebnisse der beiden etablierten Verfahren sind allerdings nur bis zu einem relativ geringen Vereinfachungsgrad verwendbar, wenn eine gegebene Fehlertoleranz nicht überschritten werden soll. Das dritte, angepasste Verfahren erzeugt Geometriemodelle, deren Effekt auch für Modellversionen mit sehr wenigen Dreiecken mit dem Effekt des initialen Modells annähernd übereinstimmt.
Die präsentierten Ergebnisse basieren auf den Arbeiten im DGMK-Projekt 771 und das gezeigte 3D-Modell zweier Salzstöcke im Gifhorner Trog wurde von unseren Projektpartnern zur Verfügung gestellt.
Keywords: Mesh-Simplification, Potentialfeldmodellierung, geometrische 3D Modellierung
  • Lecture (Conference)
    DGMK/ÖGEW-Frühjahrstagung 2016, Fachbereich Aufsuchung und Gewinnung, 21.-22.04.2016, Celle, Deutschland
  • Contribution to proceedings
    DGMK/ÖGEW-Frühjahrstagung 2016, Fachbereich Aufsuchung und Gewinnung, 21.-22.04.2016, Celle, Germany
    DGMK-Tagungsbericht 2016-1, Hamburg: DGMK, 978-3-941721-64-7, 97-104

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Permalink: https://www.hzdr.de/publications/Publ-24776
Publ.-Id: 24776


Nickel-Enhanced Graphitic Ordering of Carbon Ad-Atoms during Physical Vapor Deposition

Wenisch, R.; Hübner, R.; Munnik, F.; Gemming, S.; Abrasonis, G.; Krause, M.
Compatibility with commonly used substrate materials is of crucial importance for graphene device production. Low-temperature synthesis approaches are needed to cope with this challenge. Therefore it has to be clarified, to which extend physical vapor deposition can be used to produce ordered graphene structures.

In this contribution, the mechanism of graphitic ordering of atomic C on Ni was investigated at temperatures ranging from room temperature to 550 °C. The C/Ni films were prepared by ion beam sputtering. A temperature-induced and a Ni-induced enhancement of graphitic ordering is demonstrated. The Ni-effect is responsible for the formation of a bi-layer structure of the C films at higher deposition temperatures. In the bi-layers, C forms graphenic planes parallel to the Ni surface within a thickness range of 1-2 nm. Further deposited C grows preferentially perpendicular to the surface. The results are discussed on the basis of hyperthermal atom deposition, surface diffusion, metal-induced crystallization and dissolution-precipitation. Our findings point to a dominating role of surface diffusion-assisted crystallization in the carbon ordering process.
Keywords: graphitic carbon, graphene, physical vapour deposition, Raman, TEM
  • Poster
    International Winterschool on Electronic Properties of Novel Materials 2016, 13.-20.02.2016, Kirchberg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-24775
Publ.-Id: 24775


Helmholtz Institute Freiberg for Resource Technology - Helmholtz-Zentrum Dresden-Rossendorf - Introduction

Kelly, N.
Helmholtz Institute Freiberg for Resource Technology
Helmholtz-Zentrum Dresden-Rossendorf
Introduction
  • Lecture (others)
    Meeting FWGM und UIT, 06.01.2017, Freiberg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24774
Publ.-Id: 24774


Radiation oncology in the era of precision medicine

Baumann, M.; Krause, M.; Overgaard, J.; Debus, J.; Bentzen, S. M.; Daartz, J.; Richter, C.; Zips, D.; Bortfeld, T.
Technological advances and clinical research over the past few decades have given radiation oncologists the capability to personalize treatments for accurate delivery of radiation dose based on clinical parameters and anatomical information. Eradication of gross and microscopic tumours with preservation of health-related quality of life can be achieved in many patients. Two major strategies, acting synergistically, will enable further widening of the therapeutic window of radiation oncology in the era of precision medicine: technology-driven improvement of treatment conformity, including advanced image guidance and particle therapy, and novel biological concepts for personalized treatment, including biomarker-guided prescription, combined treatment modalities and adaptation of treatment during its course.

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Permalink: https://www.hzdr.de/publications/Publ-24773
Publ.-Id: 24773


Magnetic anisotropy of III-Mn-V dilute ferromagnetic semiconductors

Xu, C.; Yuan, Y.; Sawicki, M.; Böttger, R.; Helm, M.; Zhou, S.
As one of the most important physical properties of III-Mn-V dilute ferromagnetic semiconductors (DFS), the magnetic anisotropy could be tailored by Mn/hole concentrations and by the lattice strain [1, 2]. Particularly, the crystal symmetry lowering in-plane uniaxial anisotropy still remains one of the most puzzling properties of the DFS family. Using a perturbation method and ab initio computations, Birowska et al. showed that the preferential distribution of Mn along (Ga,Mn)As [11(_)0] can produce bulk uniaxial in-plane and out-of-plane anisotropies [3]. This preferential Mn distribution is due to the fact that the nearest-neighbor Mn pair on the GaAs (001) surface has a lower energy for the [11(_)0] axis than the [110] case. However, such a preferential Mn distribution probably will not occur when the material is not grown in a layer-by-layer mode but by a liquid-phase-epitaxy-like process with the growth speed of meters per second, as for the case of ion implantation and pulsed laser melting (II-PLM) [4]. In this work, three typical III-Mn-V DFSs [(In,Mn)As, (Ga,Mn)As, and (Ga,Mn)P] are obtained through II-PLM. We find that both (Ga,Mn)P and (Ga,Mn)As samples exhibit the easy behavior in plane (as shown in Fig. 1) while the (In,Mn)As one reveals perpendicular magnetic anisotropy (not shown). The latter is attributed to the lattice strain due to lattice mismatch between the film and the substrate. The in-plane uniaxial anisotropy is much weakened for (Ga,Mn)P and (Ga,Mn)As from the magnetic hysteresis at 5 K. However, as shown in the inset to Fig. 1, the anisotropy changes with temperature increasing. More experimental results including magnetic hysteresis at different temperatures will be discussed during the conference.

Figure 1: Magnetic hysteresis along different crystalline axis for (Ga,Mn)P and (Ga,Mn)As with different Mn concentration measured at 5 K. The inset shows the magnetic remanence along different crystalline axis for the corresponding sample.
[1] M. Sawicki et al., Phys. Rev. B 70, 245325 (2004).
[2] C. Bihler et al., Phys. Rev. B 78, 045203 (2008).
[3] M. Birowska, et al., Phys. Rev. Lett. 108, 237203 (2012).
[4] M. A. Scarpulla et al., Appl. Phys. Lett. 82, 1251-1253 (2003).
Keywords: Magnetic anisotropy, dilute ferromagnetic semiconductors (DFSs), ion implantation, pulsed laser annealing
  • Lecture (Conference)
    61st Annual Conference on Magnetism and Magnetic Materials (2016 MMM), 31.10.-04.11.2016, New Orleans, United States of America

Permalink: https://www.hzdr.de/publications/Publ-24772
Publ.-Id: 24772


The magnetic anisotropy of III-Mn-V ferromagnetic semiconductors prepared by ion implantation and pulsed laser melting

Xu, C.; Yuan, Y.; Sawicki, M.; Helm, M.; Zhou, S.
As one of the most important physical properties of dilute ferromagnetic semiconductors (DFS), the magnetic anisotropy exhibits a complicated character and its origin is under continuous discussion [1, 2]. From the point of view of application, different magnetic anisotropies could meet various needs of spintronic devices. Due to different physical parameters (e.g. band gap, lattice constant) in various Mn doped III-V DMSs, various magnetic anisotropies are expected and could be tailored by Mn or hole concentrations [3-5]. To investigate this in greater detail, we prepare three typical III-Mn-V DFSs, InMnAs, GaMnAs, and GaMnP by ion implantation and pulsed laser annealing, which is a complementary approach to low-temperature molecular beam epitaxy. We report a systematic investigation on the magnetic anisotropy with the aim to understand its physical origin.

[1]. T. Dietl et al., Rev. Mod. Phys. 86, 187-251 (2014)
[2]. M. Birowska et al., Phys. Rev. Lett. 108, 237203 (2012)
[3]. U. Welp et al., Phys. Rev. Lett. 90, 167206 (2003)
[4]. M. Sawicki et al., Phys. Rev. B 70, 245325 (2004)
[5]. C. Bihler et al., Phys. Rev. B 78, 045203 (2008)
Keywords: Magnetic anisotropy, dilute ferromagnetic semiconductors (DFSs), ion implantation, pulsed laser annealing
  • Lecture (Conference)
    European Materials Research Society (E-MRS) 2016 Spring Meeting, 02.-06.05.2016, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-24771
Publ.-Id: 24771


A Combined Spectroscopic/Molecular Dynamic Study for Investigating a Methyl Carboxylated PEI as a Potential Uranium Decorporation Agent

Lahrouch, F.; Chamayou, A. C.; Creff, G.; Duvail, M.; Hennig, C.; Lozano Rodriguez, M. J.; Den Auwer, C.; Di Giorgio, C.
Natural uranium has a very limited radioactive dose impact but its chemical toxicity due to chronic exposure is still a matter of debate. Once inside the human body, the soluble uranium, under its uranyl form (U(VI)), is quickly removed from the blood system, partially excreted from the body and partially retained in targeted organs, i.e. the kidneys and bone matrix essentially. It is then crucial to remove or prevent the incorporation of uranium in these organs in order to limit the long term chronic exposure. A lot of small chelating agents such as aminocarboxylate (PACA), catecholamide (CAM) and hydroxypyridonate (HOPO) have been developed so far. However they suffer from poor selectivity and targeting abilities.
Macromolecules and polymers are known to present a passive accumulation (size related), i.e. the so-called EPR (Enhanced Permeability and Retention) effect, towards the main organs, which can be used as indirect targeting. Very interestingly, the methyl carboxylated polyethyleneimine (PEI-MC) derivative, has been described as a potent sequestering agents for heavy metals. It would be therefore an interesting candidate to evaluate as a new class of decorporation agents with passive targeting capabilities matching uranium preferential sequestering sites. In the present work, we have explored the ability of a highly functionalized (89% rate) PEI-MC to uptake U(VI) close to physiological pH using a combination of analytical and spectroscopic techniques (ICP-OES, Inductively Coupled Plasma Optical Emission Spectrometry; EXAFS, Extended X-Ray Absorption Fine Structure; and FT-IR, Fourier transformed Infra-Red) together with molecular dynamics (MD) simulation. A maximum loading of 0.47 mg U(VI) per mg of PEI-MC has been determined by ICP-OES measurements. From FT-IR data, a majority of monodentate coordination of the carboxylate functions of the PEI-MC seems to occur. From EXAFS and MD, a mix of mono and bidentate coordination mode has been observed. Note that agreement between the EXAFS metrical parameters and MD radial distribution functions is remarkable. To the best of our knowledge, this is the first comprehensive structural study of a macromolecular PEI based agent considered for uranium decorporation purposes.
Keywords: methyl carboxylated polyethyleneimine, uranium, ICP-OES, EXAFS, FT-IR, molecular dynamics

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Permalink: https://www.hzdr.de/publications/Publ-24770
Publ.-Id: 24770


LWFA and laser-thomson scattering experiments at HZDR

Irman, A.
I present recent status of laser wakefield acceleration and laser-thomson scattering experiments at HZDR.
  • Lecture (Conference)
    Laboratory for Laser- and beam-driven plasma Acceleration Workshop, 21.-22.06.2016, Wismar, Germany

Permalink: https://www.hzdr.de/publications/Publ-24769
Publ.-Id: 24769


New insights into a historical mine site: the Sn-W-Li Zinnwald/Cínovec deposit, eastern Erzgebirge, central Europe

Neßler, J.; Seifert, T.; Gutzmer, J.
The historically significant Sn-W-Li Zinnwald/Cínovec deposit is characterised by greisen-type mineralization hosted within the apical portion of a small granite intrusion. Similar to other granitic stocks with Sn-W mineralization in the Erzgebirge, the Zinnwald granite intruded during the post- collisional stage of the late-Variscan (Permo-Carboniferous) magmatic evolution. These small Li-F granite bodies are characterised by the prominent enrichment of incompatible elements (F, Li, Rb, Cs, Sn, Nb, Ta) and the depletion of Ba, P, Sr, Zr, Ti, and Mg [1].
The Zinnwald granite is located in the eastern part of the Erzgebirge-Fichtelgebirge anticline and consists of highly evolved, weakly peraluminous and variably altered albite-Li mica leucogranite of anorogenic- type affiliation. Laterally extensive pegmatitic veins, which are located in the apical part of the granite cupola, represent the dominant source for the historically exploited Sn-W mineralisation, whereas sheet-like, metasomatic greisen ore bodies serve as a major resource for Li due to the abundance of Li- mica (zinnwaldite). This was demonstrated recently by extensive exploration of the Li mineralisation carried out by SolarWorld Solicium GmbH (SWS) during 2011 and 2014 [2].
This contribution aims to present new insights into the architecture, mineralization and geochemistry of the Zinnwald deposit based mainly on recent and historic drill core samples and their analysis by light microscopy and scanning electron microscopy, EPMA, LA-ICP-MS and whole rock ICP-MS. The results indicate an orientation of greisen ore bodies and veins parallel to the granite contact as well as a decrease of mineralization thickness and abundance with depth. While the host granite itself is highly evolved in its composition, progressive greisenization (Fig. 1) is accompanied by a decrease of fractionation indices (e.g. K/Rb from 20 to 8) and increasing contents of incompatible elements. For instance, mean grades of the most abundant quartz-mica-topaz-greisen include 3,700 ppm Li, 70 ppm Cs and 3.1 wt.% F. Fluid-controlled metasomatic processes are inferred from microscopic textures, trace element behaviour and significant tetrad-effect in normalized REE patterns. The chemical composition of Li-mica is similar for various greisenized lithologies of the endo- and exocontact, and Li concentrations range from 1.1 to 2.2 wt.%. Greisenization, which corresponds to the formation of zinnwaldite, follows an incipient stage of quartz-replacement and is spatially related, but not genetically linked, to disseminated Sn-W mineralization. This is demonstrated by the presence of disseminated Sn-W mineralization hosted either by greisen lithologies or by albite granite, which was only moderately affected by greisenization. This, in turn, may require a critical assessment of current metallogenetic models.
References
[1] Seifert, Th., Kempe, U (1994) Beiheft z. European Journal of Mineralogy, 6 (2): 125-172 [2] Neumann, M. et al. (2014) Unpublished resource report, pp. 204
[3] Grunewald, V. (1978) Unpublished report, Geological Archive LfULG - EB 1391, pp. 190
  • Open Access Logo Contribution to proceedings
    International Geological Congress, 27.08.-04.09.2016, Cape Town, South Africa
    Proceedings of the International Geological Congress, Washington: AGI

Permalink: https://www.hzdr.de/publications/Publ-24768
Publ.-Id: 24768


Redshifting and harmonic radiation in the nonlinear laser-thomson scattering interaction

Irman, A.
Thomson scattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also serves as a laboratory for strong field physics and nonlinear interactions. We present high resolution angle and energy resolved measurements on the laser-Thomson x-ray distribution generated by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating laser pulses from the 150 TW DRACO Ti:Sapphire laser system. As we increase the laser intensity, the electrons start to move in more complex trajectories resulting to emission of x-ray photons at higher harmonics which extends beyond 24 keV. Furthermore the overall radiation spectrum shows the broadening and redshift effect as predicted in the theory of intense laser-relativistic electron interaction in the classical picture. The amount of scattered photon also increases one order of magnitude to 106 photons per shot in the full opening emission angle.
Keywords: Laser-Thomson scattering, DRACO laser, ELBE accelerator
  • Lecture (Conference)
    17th Advanced Accelerator Concepts Workshop, 31.07.-05.08.2016, National Harbor, Maryland, USA

Permalink: https://www.hzdr.de/publications/Publ-24767
Publ.-Id: 24767


Phosphate mineralization in the Vergenoeg fluorite deposit (RSA) and its implication for the origin of REE-bearing fluid alteration

Höfig, T. W.; Krause, J.; Kern, M.; Birtel, S.; Gutzmer, J.
The Vergenoeg volcanic pipe, located in the central part of the Bushveld Complex (Republic of South Africa), hosts one of the economically most significant fluorite deposits on Earth. Its iron-oxide – fluorite – fayalite assemblage is well known for marked enrichment of rare-earth elements (REE) and phosphate. Previous studies reported the presence of apatite and a number of REE-rich accessory minerals, particularly phosphates [1, 2, 3]. Here we present a systematic study of REE-phosphates (monazite, xenotime) from the hematite-fluorite zone of the Vergenoeg orebody. Links between mineral che mi cal variations, paragenesis, and microstructural aspects are examined. The results are used to elucidate the genesis of REE-phosphate mineralization in the Vergenoeg fluorite deposit.
For this study, both apatite-bearing and apatite-free samples from the hematite-fluorite zone were selected.Scanning electronmicroscopy-based image analysis has been performed in order to identify and spatially map the distribution of rare-earth phosphates as well as rock-forming minerals throughout the samples in polished sections. Subsequently, the mineral chemistry of the phosphates has been determined by means of electron probe microanalysis.
Two major fabric type scan be distinguished:First,fine-grained monazite and xeno time form euhedral pseudomorphs in the presence or absence of apatite. Second, they occur as infill of interstices and microfractures. Mineral associations of monazite with xenotime, iron-oxide, fluorite or their joint assemblage have been identified,applying to every fabric type.The combination of mineral chemistry data and microstructural observations suggests a link between the spatial occurrence of REE-phosphates and their chemical composition. Different mineral associations also have an effect on the chemical composition. In addition, the deportment of certain elements suggests microstructural and mineralogical changes as controlling factors, respectively.
The mineral chemistry of monazite is inline with the monazite-(Ce)of type 2 from Graupner et al. [3]. Xenotime data point to Y-rich compositions, corresponding to the secondary xenotime generation proposed by Graupner et al. [3]. Besides regular monazite, the presence of grains with comparatively low analytical totals between c. 90 wt% and 98 wt% may reflect altered compositions, resulting from hydration under low-temperature conditions giving rise to formation of hydrated monazite (or even rhabdophane) [e.g., 4, 5]. Similarly low analytical totals for xenotime may also represent hydration. Increasing sulfur contents with decreasing analytical totals for both rare-earth phosphates indicate enhanced sulfur activity of the overprinting fluid.
References:

[1]FouriePJ(2000)In:Hydrothermal Iron Oxide Copper Gold & Related Deposits:A Global Perspective: Australian Mineral Foundation, Adelaide, 309–320
[2] Goff BH et al. (2004) Miner Petrol 80: 173–199
[3] Graupner T et al. (2015) Ore Geol Rev 64: 583–601
[4] Krenn E and Finger F (2007) Lithos 95: 130–147 [5] Berger A et al.(2008)Chem Geol 254:238–248
  • Open Access Logo Contribution to proceedings
    International Geological Congress, 27.08.-04.09.2016, Cape Town, South African
    Proceedings of the International Geological Congress, Washington: American Geoscience Institute

Permalink: https://www.hzdr.de/publications/Publ-24766
Publ.-Id: 24766


Self-assembly of periodic nanostructure arrays based on ion-induced spontaneous surface nanopatterning

Erb, D.; Ou, X.; Schlage, K.; Lenz, K.; Röhlsberger, R.; Lindner, J.; Facsko, S.; Helm, M.; Fassbender, J.ORC
Nanopatterning of different materials is a key requirement in research fields as diverse as magnetism, plasmonics, optics or catalysis. Potential technological applications range from photovoltaics augmented by light trapping [1] to high-sensitivity biomolecule detection using plasmonic signal enhancement [2] and high-speed low-energy information encoding, transmission, and processing based on magnonic crystals [3]. Industrial-scale fabrication of such devices for energy harvesting, medical diagnostics, or information technology requires nanopatterning processes which are fast, facile, cost-effective, scalable, and highly reproducible. A versatile bottom-up nanopatterning approach which can meet these demands is based on ion irradiation of semiconductor surfaces and well-established thin film deposition techniques.

On crystalline semiconductor substrates, nanoscale surface patterns with well-defined lateral periodicity form via the mechanism of reverse epitaxy, i.e. the non-equilibrium self-assembly of vacancies and ad-atoms under ion irradiation [4]. The GaAs(001) surface exhibits highly uniform faceting and therefore lends itself to transferring this pattern regularity to other materials. The nanopatterned GaAs surface can for instance be employed as a substrate for molecular beam epitaxy under grazing incidence, producing arrays of nanodots, nanowires, periodically corrugated thin films, or combinations thereof by geometrical shading. It can also be the basis for hierarchical self-assembly: here, the topography of the GaAs surface provides a preferential direction for the chemical microphase separation in a diblock copolymer thin film. This flat film then serves as a highly ordered chemical template for metal nanostructure growth in a variety of pattern morphologies [5]. The large-area periodically nanopatterned sample systems are especially very well suited for x-ray and neutron scattering experiments.

In this contribution, we outline the reverse epitaxy mechanism and present examples of how the resulting surface nanopatterns can be employed in the fabrication of nanostructure arrays. We hope to stimulate discussion of further applications by emphasizing the simplicity and versatility of this bottom-up approach.

[1] H.A. Atwater and A. Polman, Nature Materials 9 (2010)
[2] J. Vogt et al., Phys. Chem. Chem. Phys. 17 (2015)
[3] D. Grundler, Nature Physics 11 (2015)
[4] X. Ou et al., Nanoscale 7 (2015)
[5] D. Erb et al., Science Advances 1 (2015)
  • Poster
    MML workshop, 14.-16.12.2016, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24765
Publ.-Id: 24765


Quantifying the resource potential of flotation tailings storage facilities – the role of geometallurgical characterization

Gutzmer, J.; Osbahr, I.; Leißner, T.; Satgé, L.; Unger, G.; Büttner, P.
Flotation is the most widely applied separation process in today’s raw materials industry. Billions of tons of flotation tailings are produced every year. As fine-grained residues these are usually deposited in large-scale tailings storage facilities (TSLs). With recoveries commonly below 90%, a significant portion of the value contained in the primary ore finds its way into such TSLs. In addition, commodities that were not targeted by the primary exploitation process may later become valued products. There are many well-known examples of historic tailings (or other mining-related residues) becoming economically attractive targets of renewed exploitation. Arguably the most prominent of these examples is the recovery of gold and uranium from slimes and sand storage facilities of the Witwatersrand goldfields, South Africa. TSLs are thus best described as large, low-grade anthropogenic ore bodies; they are also a prime example of an urban mine.

Retreatment of tailings offers some significant advantages. Very large tonnages of readily milled material are available at surface. Volume and average grade are usually well-known, thus reducing exploration expenses and technical risk. Added economic benefit may be the release of land previously covered by TSLs for development. There are also environmental benefits as particular components identified as environmental risk may be removed and remaining residues transferred into TSLs that comply with modern environmental legislation.

There are, however, also some tangible risks associated with retreatment of materials from TSLs. Most importantly, the value components that have escaped previous separation efforts are likely to be difficult to concentrate. Reasons for losses are manifold, but may include poor liberation or very fine grain size of ore minerals or complex deportment of target metals into various minerals. Furthermore, ore minerals may experience surface alteration processes whilst contained in TSLs for extended periods of time. Such processes result in the development of surface coatings or even complete transformation of primary ore mineral assemblages into a complex paragenesis of secondary products. Ultimately, such processes lead to a complex overprint of the inherent primary stratification related to tailings deposition by a secondary stratification that resembles supergene oxidation and cementation zones.

Given the above it appears only reasonable that TSFs should be exposed to careful geometallurgical characterization prior to retreatment [1]. This contribution will present two examples from the Ore Mountains, Germany [2]. Two large TSLs were systematically drilled; the tailings materials were subjected to comprehensive characterization. 3D models were constructed for the TSLs based on novel recoverability indices that take into account not only grade, but also other tangible characteristics of the tailings material, such as liberation and grain size of value components. In this manner, opportunities and limitations of intended retreatment can be constrained – and an optimal retreatment strategy developed.

References:
[1] Louwrens E et al. (2015) in: Tailings and mine waste management for the 21st Century, AUSIMM, 99-106
[2] http://www.r3-innovation.de/de/15499
  • Open Access Logo Contribution to proceedings
    International Geological Congress, 27.08.-04.09.2016, Cape Town, South Africa
    Quantifying the resource potential of flotation tailings storage facilities – the role of geometallurgical characterization, Washington: American Geosciences Institute

Permalink: https://www.hzdr.de/publications/Publ-24764
Publ.-Id: 24764


Disentangling magnetic order on nanostructured surfaces

Erb, D.; Schlage, K.; Bocklage, L.; Hübner, R.; Merkel, D.; Wille, H.-C.; Rüffer, R.; Röhlsberger, R.
Nanopatterned magnetic materials are of considerable interest for both academic research and industrial application. We present a novel technique, combining Nuclear Resonant Scattering (NRS) [1] and GISAXS [2], which allows disentangling the magnetic properties of distinct structural units in a nanopatterned system. The underlying idea is to exploit the fact that the nuclear resonant signal (carrying the magnetic information) undergoes the same scattering in q-space as the electronic signal (carrying the structural information). Thus, photons scattered resonantly from different structural units of the sample are separated due to the sample morphology and can be detected at different positions in the scattering pattern. To demonstrate this principle, we fabricated a 57Fe thin film sample with alternating thick and thin stripe-like regions, i.e. with heterogeneous structural and magnetic properties, which vary periodically on the nm-scale. We investigated the sample in-situ during growth (beamline ID18, ESRF) and studied its response to external magnetic fields ex-situ (beamline P01, PETRA III). During film growth, we observed the onset of ferromagnetic ordering first in the thicker regions, then in the thinner regions. Upon applying an external magnetic field, the magnetic moments in thick and thin regions are displaced from the easy axis of magnetization to different extents [3, 4]. Our experiments thus show that nuclear resonant GISAXS is a sensitive method for obtaining information about the magnetic state of individual nm-scaled parts of a magnetically heterogeneous sample.

[1] R. Röhlsberger, Springer Tracts in Modern Physics 208 (2004)
[2] G. Renaud, R. Lazzari, and F. Leroy, Surface Science Reports 64 (2009) 255
[3] D. Erb, Ph.D. thesis, University of Hamburg (2015)
[4] manuscript in preparation
  • Poster
    GISAXS2016 workshop, 16.-18.11.2016, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24763
Publ.-Id: 24763


Laser wakefield with external bunch injection, status 2016 (work in progress)

Irman, A.
Recent progress of laser wakefield acceleration with external bunch injection at HZDR is presented
Keywords: laser wakefield, RF linear-accelerator
  • Lecture (Conference)
    3rd EuCard-2 Annual meeting, 26.-28.04.2016, University of Malta, Malta

Permalink: https://www.hzdr.de/publications/Publ-24762
Publ.-Id: 24762


The EIT Raw Materials

Gutzmer, J.
Invited lecture - no abstract
  • Lecture (others)
    Annual Graduation Ceremony of Emerald MSc Students, 23.-24.08.2016, Liege, Belgium

Permalink: https://www.hzdr.de/publications/Publ-24761
Publ.-Id: 24761


A systematic investigation of the magnetic anisotropy of III-Mn-V dilute ferromagnetic semiconductors

Xu, C.; Yuan, Y.; Sawicki, M.; Helm, M.; Zhou, S.
As one of the most important physical properties of dilute ferromagnetic semiconductors (DFS), the magnetic anisotropy exhibits a complicated character and its origin is under continuous discussion [1, 2]. From the point of view of application, different magnetic anisotropies could meet various needs of spintronic devices. Due to different physical parameters (e.g. band gap, lattice constant) in various Mn doped III-V DMSs, various magnetic anisotropies are expected and could be tailored by Mn or hole concentrations [3-5]. To investigate this in greater detail, we prepare three typical III-Mn-V DFSs, InMnAs, GaMnAs, and GaMnP by ion implantation and pulsed laser annealing, which is a complementary approach to low-temperature molecular beam epitaxy. We report a systematic investigation on the magnetic anisotropy with the aim to understand its physical origin.

[1]. T. Dietl et al., Rev. Mod. Phys. 86, 187-251 (2014)
[2]. M. Birowska et al., Phys. Rev. Lett. 108, 237203 (2012)
[3]. U. Welp et al., Phys. Rev. Lett. 90, 167206 (2003)
[4]. M. Sawicki et al., Phys. Rev. B 70, 245325 (2004)
[5]. C. Bihler et al., Phys. Rev. B 78, 045203 (2008)
Keywords: Magnetic anisotropy, dilute ferromagnetic semiconductors (DFSs), ion implantation, pulsed laser annealing
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft 2016, 06.-11.03.2016, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24760
Publ.-Id: 24760


Das Helmholtz Institut Freiberg für Ressourcentechnologie: Status und Ausblick

Gutzmer, J.
No abstract - invited lecture
  • Lecture (others)
    Jahrestagung der Praxispartner, Interdisziplinäres Ökologisches Zentrum, 28.04.2016, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-24759
Publ.-Id: 24759


Reverse epitaxy: Nanopattern formation by vacancy self-assembly upon low energy ion irradiation of crystalline semiconductor surfaces

Erb, D.; Engler, M.; Ou, X.; Facsko, S.
Uniform crystalline nanostructures are sought-after in many fields of research and technology, ranging from ranging from catalysis [1] to electronics [2]: crystalline nanostructures have the potential of becoming the building blocks of future information technology or of boosting development in energy conversion and storage.

Crystalline nanostructures are successfully grown in wet-chemical procedures [3] or by molecular beam epitaxy (MBE) [4]. Reverse epitaxy [5,6] is an alternative approach to fabricating highly ordered arrays of crystalline nanostructures on large areas of semiconductor surfaces. In contrast to ion irradiation under non-normal incidence at room temperature, where ripples are formed on the amorphized semiconductor surface [7], reverse epitaxy occurs at substrate temperatures above the recrystallization temperature, which ensures that the semiconductor surface retains its crystallinity.
Based on the kinetically restricted diffusion (Ehrlich-Schwoebel barrier for crossing atomic steps) of vacancies created by low energy ion irradiation, this subtractive process is considered analogous and complementary to the additive homoepitaxial growth via MBE. The resulting nanostructure morphology can be controlled via easily accessible parameters such as substrate material, surface orientation, temperature, ion species and fluence. Possible morphologies include sawtooth facets and square or hexagonal pyramidal pits with feature sizes of a few tens of nanometers.

We discuss the underlying principles and the mechanism of nanostructure formation by reverse epitaxy. The variety of nanopatterned morphologies on different semiconductor surfaces will be highlighted. We hope to stimulate discussion by presenting recent examples of our research and proposing possible applications.

[1] H. G. Yang et al., Nature 453, 638 (2008)
[2] Y. Huang et al., Science 291, 630 (2001)
[3] W. Li et al., Nanotechnology 27, 324002 (2016)
[4] C. Teichert, Phys. Rep. 365, 335 (2002)
[5] X. Ou et al., Phys. Rev. Lett. 111, 016101 (2013)
[6] X. Ou et al., Nanoscale 7, 18928 (2015)
[7] W. L. Chan et al., J. Appl. Phys. 101, 121301 (2007)
  • Invited lecture (Conferences)
    24th International Conference on the Application of Accelerators in Research and Industry, 30.10.-04.11.2016, Fort Worth, USA

Permalink: https://www.hzdr.de/publications/Publ-24758
Publ.-Id: 24758


Compositional Data Analysis: introduction and applications (and some practice)

Tolosana-Delgado, R.
This lecture will cover the fundamental aspects of compositional data analysis, from brief theoretical concepts to most widely used statistical analysis tools. Concepts will be illustrated with examples from Sediment Provenance Analysis. These will include estimating modal compositions, building confidence regions and drawing them in ternary diagrams, developing supervised classification methods to infer the origin of a sediment out of its (bulk or varietal grain) composition, and establishing regression models to describe compositional linear processes such as comminution and weathering.
Keywords: alr, centered logratio, principal components, sediment provenance, spurious correlation
  • Invited lecture (Conferences)
    Sedimentary Provenance Analysis (short course), 21.-23.09.2016, Göttingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24757
Publ.-Id: 24757


Recent progress on laser cooling of relativistic Lithium-like 12C3+ ion beams at heavy ion storage ring CSRe

Wen, W. Q.; Wang, H. B.; Huang, Z. K.; Zhang, D. C.; Hai, B.; Zhu, X. L.; Chuai, X. Y.; Zhao, D. M.; Yang, J.; Li, J.; Li, X. N.; Mao, L. J.; Mao, R. S.; Wu, J. X.; Xia, J. W.; Yang, J. C.; Yuan, Y. J.; Zhao, H. W.; Zhao, T. C.; Eidam, L.; Loeser, M.; Rein, B.; Siebold, M.; Winters, D.; Bussmann, M.ORC; Ma, X. W.
aser cooling of relativistic heavy ion beams at storage rings is one of the most promising techniques to reach high phase-space densities and achieve phase transition, ordered beam even crystalline beam. Compared with the established cooling schemes at storage rings, such as stochastic cooling and electron cooling, laser cooling has many advantages such as fast-cooling, ultra-strong cooling force and providing an ultra-low temperature(m K) ion beams. In addition, the precision laser spectroscopy of the highly charged ions can be performed by using the laser-cooled ion beams during the laser cooling experiments. We introduce the experimental principal and methods of laser cooling of relativistic ion beams at the experimental cooler storage ring of the CSRe at the Institute of Modern Phyics, Chinese Academy of Sciences. The first experimental results from a beam time aiming for laser cooling of 122 Me V/u Li-like 12C3+ at the CSRe with a pulsed laser are presented, and laser cooling and precision laser spectroscopy of relativistic Li-like and Na-like highly charged ions at the future large facility HIAF and FAIR are outlined.
Keywords: laser cooling, relativistic, ion beam

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Permalink: https://www.hzdr.de/publications/Publ-24756
Publ.-Id: 24756


Hierarchical self-assembly: Three steps to highly ordered arrays of uniform metal nanostructures

Erb, D.; Schlage, K.; Röhlsberger, R.
Nanopatterning via self-assembly has gained considerable interest as an alternative to lithography-based techniques for nanostructure fabrication. We propose a procedure for producing highly ordered arrays of uniform metallic nanostructures based exclusively on three subsequent self-assembly processes [1]: crystal surface reconstruction, copolymer microphase separation, and metal diffusion on chemically heterogeneous surfaces. The versatile approach allows for preparing nanostructures with scalable sizes and in a variety of shapes and materials. With this high-throughput technique, nanopatterns covering areas of several square centimeters can be fabricated easily.
We present results of in-situ structural and magnetic investigations of Fe nanodot arrays during formation by grazing incidence small angle X-ray scattering [2] and nuclear resonant scattering of synchrotron radiation [3], examining the dependence of the nanodot shape on deposition conditions and observing the evolution of magnetic moment dynamics during nanodot growth [4]. Possible applications of self-assembled nanopatterns could range from high-density magnetic data storage to catalysis or sensing based on surface plasmon resonance.

[1] D. Erb, K. Schlage, R. Röhlsberger, Science Advances 1 (2015) e1500751
[2] G. Renaud, R. Lazzari, and F. Leroy, Surface Science Reports 64 (2009) 255
[3] E. Gerdau and H. de Waard (eds.), Hyperfine Int. 123-124 (1999)
[4] D. Erb, Ph.D. thesis, University of Hamburg (2015)
Keywords: self-assembly diblock copolymers metal nanostructures
  • Lecture (Conference)
    International Conference on Solid Films and Surfaces, 28.08.-02.09.2016, Chemnitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24755
Publ.-Id: 24755


Comparison of Atomistic Quantum Transport and Numerical Device Simulation for Carbon Nanotube Field-effect Transistors

Fuchs, F.; Zienert, A.; Mothes, S.; Claus, M.; Gemming, S.; Schuster, J.
Carbon nanotube field-effect transistors (CNTFETs) are studied using atomistic quantum transport simulation and numerical device simulation. The studied CNTFETs consist of n-doped source- and drain-electrodes with an ideal wrap-around gate. Both the off- as well as the on-currents are described in very good agreement by both methods, which verifies the employed simplified approach in the numerical device simulation. The off-current is strongly dependent on interband tunneling in the studied CNTFETs. Thus, the good agreement between the methods verifies the tunneling model in the numerical device simulator, which can therefore be used to describe other tunneling devices, too. On the basis of the two methods we also discuss the effect of different channel lengths and aggressive gate scaling.
Keywords: carbon nanotube, field-effect transistor, numerical device simulation, atomistic quantum transport simulation
  • Contribution to proceedings
    Simulation of Semiconductor Processes and Devices (SISPAD), 06.-08.09.2016, Nürnberg, Deutschland
    Proceedings of SISPAD: IEEE, 978-1-5090-0818-6
    DOI: 10.1109/SISPAD.2016.7605197
  • Poster
    Simulation of Semiconductor Processes and Devices (SISPAD), 06.-08.09.2016, Nürnberg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24754
Publ.-Id: 24754


Investigation of Carbon Nanotube Field-effect Transistors Using Atomistic Quantum Transport and Numerical Device Simulation

Fuchs, F.; Zienert, A.; Schuster, J.; Mothes, S.; Claus, M.; Gemming, S.
Carbon nanotube based field-effect transistors (CNTFETs) are studied by using atomistic quantum transport simulation and numerical device simulation. Atomistic simulations are based on the non-equilibrium Green’s functions formalism, where self-consistent extended Hückel theory is used [1]. We apply a parameter set previously developed in our group to describe contacts between metals and carbon nanotubes with a density functional theory (DFT)-like accuracy [2]. Numerical device simulations based on the effective-mass Schrödinger equation are done for comparison [3] to highlight the strengths but also the limitations of this widely used method.
The studied CNTFETs consist of n-doped source- and drain-electrodes together with an ideal wrap-around gate. Thus, the transistor exhibits Ohmic contacts and is comparable to the one studied experimentally by Lu et al. [4]. Different CNTs with diameters ranging from 0.5 nm (7,0-CNT) to 1.3 nm (16,0-CNT) are compared. For larger diameters, band-to-band tunneling (BTBT) takes place, leading to ambipolar transfer characteristics. For small diameters, however, states within the channel are strongly localized and the BTBT is subsequently suppressed, resulting in very high on/off ratios of about 107 and ideal unipolar transfer characteristics. We investigate how different device parameters influence the device performance and show that the studied CNTFET shows excellent properties for channel lengths down to 8 nm and for a very small gate electrode of only 0.4 nm length. Finally, a comparison between the atomistic model and numerical device simulation is given. We show that the on- and off-currents are described in very good agreement and discuss the differences with respect to the switching behavior.
[1] Calculations performed using Atomistix ToolKit 12.8 (www.quantumwise.com)
[2] Zienert et al., Nanotechnology 25 (2014)
[3] Claus et al., Journal of Computational Electronics 13 (2014)
[4] Lu et al., Journal of the American Chemical Society 128 (2006)
Keywords: carbon nanotubes, numerical device simulation, atomistic quantum transport simulation, electron transport, field-effect transistors
  • Lecture (Conference)
    11th International Symposium on Computational Challenges and Tools for Nanotubes, 28.08.-02.09.2016, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-24753
Publ.-Id: 24753


An Atomistic Model for Carbon Nanotube Based Field-effect Transistors: Interband Tunneling and Device Scaling

Fuchs, F.; Zienert, A.; Schuster, J.; Gemming, S.
We study carbon nanotube based field-effect transistors (CNTFETs) consisting of n-doped source and drain electrodes together with an ideal wrap-around gate. This system is comparable to the one studied experimentally by Lu et al. [1] and is our model for comparing different simulation approaches. In this contribution, we present our results based on a fully atomistic quantum transport model.
Carbon nanotubes (CNTs) with diameters ranging from 0.5 nm to 1.3 nm, which corresponds to the (7,0) CNT and (16,0) CNT, respectively, are studied. We find that in case of thick CNTs, the band-to-band tunneling (BTBT) strongly increases the leakage current in the off-state. This leads to ambipolar transfer characteristics in agreement with experimental results1. Concerning very thin CNTs, the BTBT has not been studied in much detail, yet. We demonstrate that for these kind of CNTs, states within the channel are strongly localized. They do not allow carrier transport and thus suppress the BTBT, which results in ideal unipolar transfer characteristics and on/off ratios of about 107.
We furthermore present a systematic investigation of the relation between device parameters and the resulting transistor characteristics, which can guide future device scaling. Thin CNTs for example allow outstanding device properties even for short channel lengths down to 8 nm. It is crucial to maintain channel control in ultra-scaled transistors. Thus, our studies also elucidate the impact of aggressive gate scaling. Even for a very small gate electrode of only 0.4 nm length, good switching properties can be preserved.
The non-equilibrium Green’s functions formalism together with self-consistent extended Hückel theory is used for the simulations. Thanks to a parameter set previously developed in our group [2], we can describe CNTs with a density functional theory-like accuracy.
[1] Lu et al., Journal of the American Chemical Society 128 (2006)
[2] Zienert et al., Nanotechnology 25 (2014)
Keywords: carbon nanotubes, field-effect transistor, extended Hückel theory, electron transport
  • Poster
    17th International Conference on the Science and Application of Nanotubes and Low-Dimensional Materials (NT16), 28.08.-02.09.2016, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-24752
Publ.-Id: 24752


Stress Analysis in Semiconductor Devices by Kelvin Probe Force Microscopy

Sheremet, E.; Fuchs, F.; Paul, S. D.; Haas, S.; Vogel, D.; Rodriguez, R. D.; Zienert, A.; Schuster, J.; Reuter, D.; Geßner, T.; Zahn, D. R. T.; Hietschold, M.
The determination of built-in strain in semiconductor devices with nanometer spatial resolution and high sensitivity is needed for the characterization of nanoscale electronic devices. Kelvin probe force microscopy (KPFM) is an atomic force microscopy-based method that provides the spatially resolved surface potential at the sample surface, fulfilling the requirements on resolution and sensitivity. The contrast observed in KPFM imaging is often attributed to stress, but there are only a few reports on the application of KPFM for quantitative stress analysis [1]. In this contribution we focus on the application of KPFM for analysis of stress in silicon devices, such as copper through silicon vias and silicon membranes. The experimental results are compared with density functional theory calculations of strained silicon. This work provides critical insights into the quantitative determination of stress at the nanoscale that so far has gone largely unnoticed in the scanning probe microscopy community.
[1] W. Li, D.Y. Li, J. Appl. Phys. 99, 073502 (2006).
Keywords: silicon, kelvin probe force microscopy, density functional theory
  • Poster
    DPG Frühjahrstagung Regensburg, 06.-11.03.2016, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24751
Publ.-Id: 24751


Electronic Structure and Transport Properties of Thin Silicon Nanowires

Fuchs, F.; Gemming, S.; Schuster, J.
Silicon nanowires (SiNWs) are promising candidates as building blocks for electronic devices. For the simulation of SiNWs, numerical device simulations, based on the silicon bulk band structure, are often used. When the diameter of the wires is reduced, however, atomistic quantum simulations become mandatory at some point. In the present work, thin hydrogen-passivated SiNWs with diameters between 1 and 6 nm are studied by means of density functional theory. It is shown that the band gap approaches the bulk value in the limit of infinitely thick nanowires and increases for thin wires due to quantum confinement. Using a radially resolved density of states it is demonstrated, that the density of states is highest in the nanowire center, where most of the current transport would occur, and decreases near the surface. Comparing the density of states between SiNWs with different diameters, the transition to bulk silicon can be observed. This justifies the use of bulk band structure approximations for thicker SiNWs, but also highlights the need for atomistic quantum simulations in case of thinner ones.
Keywords: silicon nanowire, density functional theory, quantum confinement
  • Lecture (Conference)
    DPG Frühjahrstagung Regensburg 2016, 06.-11.03.2016, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24750
Publ.-Id: 24750


Experimentelle Untersuchung zum Stofftransport in einer Blasensäule mittels schneller Röntgentomographie

Ayubi, M.
Die Bearbeitung des vorliegenden Beleges umfasste eine Literaturrecherche zur Hydrodynamik und Stofftransport in Blasensäulenreaktoren. Es wurden experimentelle Untersuchungen mit der ultraschnellen Röntgentomographie durchgeführt und anhand der gemessenen Daten hydrodynamische Parameter und Parameter zum Stofftransport extrahiert.
  • Study thesis
    TU Dresden, 2016
    Mentor: Ragna Kipping
    71 Seiten

Permalink: https://www.hzdr.de/publications/Publ-24749
Publ.-Id: 24749


Investigation of inertial waves inside a liquid metal column by means of electromagnetic fields

Vogt, T.; Räbiger, D.; Eckert, S.
In this study, the dynamics of inertial waves inside a cylindrical vessel was studied experimentally. The liquid metal GaInSn was chosen as fluid in order to enable a contactless stimulation of the flow inside the cylinder by means of electromagnetic fields. A rotating magnetic field (RMF) generates a supercritical rotating motion of the liquid. The excitation of the inertial waves is realised by means of periodic field strength modulations and by means of short intense magnetic field pulses. Furthermore, the experiment demonstrates that inertial waves may be excited spontaneously by turbulent structures in the rotating flow. The ultrasound Doppler velocimetry was used to record the flow structure and to identify the inertial waves occurring in the setup.
  • Lecture (Conference)
    International Congress of Theoretical and Applied Mechanics, 21.-26.08.2016, Montreal, Canada
  • Contribution to proceedings
    International Congress of Theoretical and Applied Mechanics, 21.-26.08.2016, Montreal, Canada

Permalink: https://www.hzdr.de/publications/Publ-24748
Publ.-Id: 24748


Higher wavenumber shift of Pb (Al1/2Nb1/2)O3 substitution in relaxor ferroelectric Pb(Zr0.52Ti0.48)O3-Pb(Zn1/3Nb2/3)O3 ceramics

Zhu, J. J.; Li, C. Q.; Jiang, K.; Zhang, P.; Tong, W. Y.; Liu, A. Y.; Shi, W. Z.; Liu, Y.; Huang, Y. P.; Li, W. W.; Hu, Z. G.
We report the lattice dynamics of 0.8Pb(Zr0.52Ti0.48)O3−(0.2−x)Pb(Zn1/3Nb2/3)O3−xPb(Al1/2Nb1/2)O3 (0.8PZT−(0.2−x)PZN−xPAN, 0.02≤x≤0.08) ceramics around morphotropic phase boundary (MPB) by infrared and Raman spectra. The dielectric functions in the wavenumbers range between 50 and 1000 cm−1 were extracted from the factorized oscillator model. The addition of PAN to PZT-PZN system introduces Al3+ ions to the B-site and all of these Raman-active modes in the measured range are related to B-site atoms vibration. The effect of PAN addition leads to infrared and Raman modes shifting to higher wavenumbers, because the atomic weight of Al is smaller than that of Zn. Therefore, the substitution of B-site atom in PZT-PZN system is the dominant reason to influence the frequency shift of infrared and Raman modes.
Keywords: PZT-based ceramics, Morphotropic phase boundary, Dispersion relation, Lattice vibrations, Raman spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-24747
Publ.-Id: 24747


Weakly turbulent Rayleigh-Bénard convection in a horizontal magnetic field

Vogt, T.; Ishimi, W.; Tasaka, Y.; Yanagisawa, T.; Sakurba, A.; Eckert, S.
MHD Rayleigh-Bénard convection was studied experimentally using a liquid metal inside a box with square horizontal cross section and aspect ratio five. Systematic flow measurements were performed by means of ultrasound Doppler velocimetry that can capture time variations of instantaneous velocity profiles. Applying a horizontal magnetic field organizes the convective motion into a flow pattern of quasi-two dimensional rolls arranged parallel to the magnetic field. If the Rayleigh number (Ra) is increased over a certain threshold Ra/Q, whereby Q is the Chandrasekhar number, the convection flow undergoes a transition to turbulence. We explore the flow structure in a weakly turbulent convection pattern by means of experiments and by means of numerical simulations.
  • Lecture (Conference)
    10th PAMIR International Conference, 20.-24.06.2016, Cagliari, Italy
  • Contribution to proceedings
    10th PAMIR International Conference, 20.-24.06.2016, Cagliari, Italy

Permalink: https://www.hzdr.de/publications/Publ-24746
Publ.-Id: 24746


Lithological units and Sn deportment of a compositionally complex skarn ore (Hämmerlein, Erzgebirge, Germany)

Kern, M.; Kästner, J.; Gutzmer, J.
The Hämmerlein seam is part of the world class Tellerhäuser deposit in the Erzgebirge, Germany, and represents a compositionally complex polymetallic Sn-In-Zn skarn. Current resources amount to 100000 t Sn at a cut-off grade of 0.2 wt. %. In addition, 2100 t of In and 270000 t of Zn have been estimated [1]. In the late 1970s, 50000 t of ore from the Hämmerlein seam were mined and processed experimentally in a pilot plant, but grade and recovery remained below expectations. Cited reasons for poor recovery the complex mineralogy and variability in grain sizes of valuable minerals [2]. The predicted rise in global Sn consumption and limited availability of high grade deposits [3] render the Tellerhäuser deposit an interesting exploration target [1]

A consortium of German research institutions currently conducts new beneficiation experiments on the Hämmerlein orebody. Determination of the Sn deportment and the characterization of the different lithological (skarn) units are the first steps in this process. For this purpose, three transects in the central part of the Hämmerlein orebody were mapped and a suite of hand specimen collected to represent all relevant lithotypes within the studied part of the orebody. Thin sections were prepared and analyzed using the Mineral Liberation Analyzer (MLA) to obtain quantitative data about mineralogy, mineral grain sizes, intergrowths, and associations. The remaining material of the hand specimen was crushed to 99 % < 250 µm. This granular material was split to produce grain mounts for further mineralogical studies and in order to prepare sample powders for geochemical analysis.

The Hämmerlein skarn orebody can be subdivided into the following three macroscopically distinct lithotypes: 1. magnetite-dominated (40 – 80 wt. % magnetite), 2. sulphide-dominated (> 20 wt. % sphalerite) and 3. silicate-dominated (> 60 wt.% silicates). In the silicate-dominated unit a gradual transition of different silicate minerals enables further discrimination of a chlorite-rich, an amphibole-chlorite-rich, an epidote-pyroxene-rich and a garnet-rich subunit. The hanging and footwall are best described as mica schist and gneiss, respectively.

The primary host mineral for Sn is cassiterite (SnO2) with grain sizes between 1 µm and 1 mm. Some of the cassiterite has fibrous crystal habit. Significant amounts (ca. 1.4 wt. %) of coarse-grained (50 µm to 1 mm) cassiterite is present in the chlorite subunit. The amphibole-chlorite subunit contains an average of 0.3 wt. % cassiterite. Samples from other parts of the Hämmerlein orebody indicate significant amounts of cassiterite in the magnetite- and the sulphide-dominated lithotypes as well.

Stokesite (CaSnSi3O9 ∙ 2H2O) is the second most abundant Sn mineral. It appears in fine-grained aggregates in the amphibole-chlorite subunit and in the magnetite-dominated ore type reaching concentrations of ca. 0.1 wt. %. Notable Sn concentrations were detected by WDX in some examples of titanite (≤ 21 wt. %), epidote (≤ 4.4 wt. %), amphibole (≤ 1.9 wt. %), garnet (≤ 2.3 wt. %), and iron oxides (≤ 2.3 wt. %).

Our preliminary results illustrate that the Sn mineralisation of the Hämmerlein skarn is indeed very complex. Cassiterite dominates, but other minerals (most notably stokesite) do contribute significantly to the deportment. Further studies will aim to quantify the variability of deportment and other resource characteristics, in order to guide mineral processing test work.
  • Lecture (Conference)
    EMC Rimini 2016, 19.-22.09.2016, Rimini, Italien
  • Contribution to proceedings
    EMC Rimini 2016, 11.-15.09.2016, Rimini, Italien

Permalink: https://www.hzdr.de/publications/Publ-24745
Publ.-Id: 24745


The Hämmerlein orebody: Lithological units and Sn deportment

Kern, M.; Kästner, J.; Gutzmer, J.
The Hämmerlein seam is part of the world class Tellerhäuser deposit in the Erzgebirge, Germany, and represents a compositionally complex polymetallic Sn-In-Zn skarn. Current resources amount to 100 000 t Sn at a cut-off grade of 0.2 wt. %. In addition, 2100 t of In and 270 000 t of Zn have been estimated [1]. In the late 1970s, 50 000 t of ore from the Hämmerlein seam were mined and processed experimentally in a pilot plant, but grade and recovery remained below expectations. Cited reasons for poor recovery the complex mineralogy and variability in grain sizes of valuable minerals [2]. The predicted rise in global Sn consumption and limited availability of high grade deposits [3] render the Tellerhäuser deposit an interesting exploration target [1].
A consortium of German research institutions is conducting new beneficiation experiments on ores from the Hämmerlein orebody. Determination of the Sn deportment and the characterization of the different units are the first step towards successful beneficiation. For this purpose, three transects in the central part of the Hämmerlein seam were mapped and sampled. Thin sections were prepared and analyzed using the Mineral Liberation Analyzer (MLA) to obtain quantitative data about mineralogy, mineral grain sizes, mineral intergrowth and mineral associations. The remaining material was crushed to 99 % < 250 µm and grain mounts were prepared for geochemical analysis and for further MLA studies.
Taking into account the amount of main ore- and/or gangue-forming minerals, following three units of the orebody have been distinguished: 1. magnetite-dominated (40 – 80 wt. % magnetite), 2. sulphide-dominated (> 20 wt. % sphalerite) and 3. silicate-dominated (> 60 wt. % silicates). In the silicate-dominated unit a gradual transition of different silicate minerals enables further discrimination of a chlorite-rich, an amphibole-chlorite-rich, an epidote-pyroxene-rich and a garnet-rich subunit. The hanging and footwall are best described as mica schist and gneiss, respectively. Both are partially overprinted and show skarn features in proximity to the skarn ore body.
Sn-bearing minerals are present in the skarn ore body as well as in the overprinted host rocks. The primary host mineral for Sn is cassiterite (SnO2) with grain sizes between 1 µm and 1 mm. Some of the cassiterite has fibrous crystal habit. Significant amounts (ca. 1.4 wt. %) of coarse-grained (50 µm to 1 mm) cassiterite are present in the chlorite subunit. The amphibole-chlorite subunit contains an average of 0.3 wt. % cassiterite. Additional samples from other parts of the Hämmerlein seam indicate significant amounts of cassiterite in the magnetite and the sulphide ore types as well. Malayaite (CaSnSiO5) is the second most abundant Sn mineral. It appears in fine-grained aggregates in the amphibole-chlorite subunit of the silicate-dominated ore type and in the magnetite-dominated ore type reaching concentrations of ca. 0.1 wt. %. Notable Sn concentrations were detected by EDX in typically Sn-free titanite, epidote and iron oxides. However, the total amount of Sn in these minerals account for less than 10 wt. % of the total Sn content of the deposit.
Our preliminary results illustrates that the Sn mineralisation of the Hämmerlein orebody is indeed very complex. The highest beneficiation potential has cassiterite and maybe malayaite, depending on the concentrations and host unit.
  • Poster
    GOOD Meeting 2016, 16.-18.03.2016, Freiberg, Deutschland
  • Contribution to proceedings
    GOOD Meeting 2016, 14.-16.03.2016, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24744
Publ.-Id: 24744


Flash lamp annealing of transparent conducting oxides and other thin films

Rebohle, L.; Schumann, T.; Prucnal, S.; Skorupa, W.
This presentation gives a short overview about the technique of flash lamp annealing in general and current activities at HZDR related to this topic. Thereby, the focus is on the possibilities to maximize the UV output of the flash lamp the use for thin semi-transparent films, namely transparent conducting oxides.
Keywords: flash lamp annealing, transparent conducting oxides, zinc oxide
  • Lecture (Conference)
    Treffen der Nutzergruppen Heißprozesse und RTP und Ionenimplantation, 08.-09.12.2016, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24743
Publ.-Id: 24743


Performance comparison between different sparger plate orifice patterns: Hydrodynamic investigation using ultrafast X-ray tomography

Möller, F.; Seiler, T.; Lau, Y. M.; Weber, M.; Weber, M.; Hampel, U.; Schubert, M.
In this work, the effect of the sparger design on the hydrodynamic performance in a bubble column of 0.1 m ID downstream a single (coarse) and multi-orifice (fine) perforated plate sparger was studied using the ultrafast X-ray tomography. The liquid was kept in semi-batch mode and the superficial gas velocity was varied between 0.011 and 0.025 m s-1 to ensure non-jetting flow through the sparger holes. The effect of the orifice patterns on the hydrodynamic performance was evaluated through bubble size distribution (BSD), radial gas holdup profile and overall gas holdup as well as Sauter mean bubble diameter and magnitude of the interfacial area. To evaluate sparger and bubble column performance, respectively, also the mass transfer was investigated. Due to the high turbulence induced by the large bubbles released from the coarse sparger, the equilibrium BSD was already reached at a dimensionless height of h/D = 1.0. However, average bubble characteristics, such as interfacial area and Sauter mean diameter, were similar for both sparger types at a column height of h/D ≥ 7.0. Based on a comprehensive hydrodynamic analysis, requirements for sparger refinement were derived depending on respective reaction rates, mixing properties, heat production and removal duty. Eventually, adapted correlations are proposed for radial holdup profile and Sauter mean diameter accounting for various plate refinements using liquids which inhibit coalesce of gas bubbles.
Keywords: Bubble column, sparger performance, hydrodynamics, ultrafast X-ray tomography, flow evolution, gas-liquid mass transfer

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Permalink: https://www.hzdr.de/publications/Publ-24742
Publ.-Id: 24742


Thermal spin transfer torque on MgO-based magnetic tunnel junctions using FMR microresonators

Cansever, H.; Fowley, C.; Narkowicz, R.; Kowalska, E.; Aleksandrov, Y.; Yildirim, O.; Titova, A.; Lenz, K.; Lindner, J.; Fassbender, J.ORC; Deac, A. M.
MgO-based magnetic tunnel junctions are commonly used in spintronic device applications, such as recent spin transfer torque random access memory (STT-RAM) because of their non-volatility, fast switching and high storage capacity. Spin transfer torque is defined as a spin polarized current flowing through a ferromagnet exerting a torque on the local magnetization. With thermal spin transfer torque (T-STT), thermally excited electron transport is used instead of spin polarized charge current and provides an interesting way of using thermoelectric effects in magnetic storage applications. Our study focuses on fundamental experimental research aimed at demonstrating that thermal gradients can generate spin-transfer torques in MgO-based magnetic tunnel junctions (MTJs). We use microresonators in order to analyze how the ferromagnetic resonance signal corresponding to the free layer of an in-plane MgO-based tunnel junction device is modified in the presence of a temperature gradient across the barrier.
This work is supported by DFG-SPP1538
Keywords: Spin Transfer Torque, MTJ, microresonator, FMR
  • Poster
    SpinCat PhD Workshop Mainz, 18.-19.08.2016, Mainz, Germany

Permalink: https://www.hzdr.de/publications/Publ-24741
Publ.-Id: 24741


Neue numerische Methoden zur Bearbeitung und 3D-Interpretation von Geodaten und -modellen in interdisziplinarer Forschung

Menzel, P.
Anhand allgemeiner und spezifischer Aufgaben und Fragen, die sich aus der Mitarbeit in den beiden Forschungsprojekten AIDA und TiPOT3D ergaben, wird in dieser Arbeit gezeigt, wie Ansätze und Verfahren aus der Geoinformatik die Prozessierung und die Interpretation der Geophysik und hier speziell der Potentialverfahren unterstützen können.
Zuerst wird gezeigt, wie die Kommunikation und Interaktion in interdisziplinären Forschungsprojekten durch Arbeiten mit Schwerpunkt Geoinformatik unterstützt warden kann. Dies erfolgt exemplarisch am BMBF-Verbundprojekt “AIDA - From Airborne Data Inversion to In-Depth Analysis”. Für die interne Projektkommunikation und Interaktion wird das “AIDA-Projekt-Wiki” vorgestellt. Es soll einerseits die Kommunikation innerhalb des Projekts unterstützen und gleichzeitig eine online-basierte Plattformzum Austausch und der Archivierung projektbezogener Daten ermöglichen. Das “AIDAProjekt-Wiki” koordiniert und archiviert die Projektkommunikation und vereinfacht die planerische Organisation von Projekttreffen, Publikationen und Tagungsteilnahmen.
Zusätzlich wurden Schnittstellen für den Austausch der verschiedenen Projektdaten zwischen den Projektteilnehmern bereitgestellt. Anhand zweier Anwendungen wird gezeigt, wie Modellinformationen zwischen verschiedenen Modellrepräsentation konvertiert werden.
Die Evaluierung geologischer 3DUntergrundmodelle mittels Dichte-Modellierungen war eines der Hauptanliegen im BMBF-Verbundprojekt. In AIDA wurde von den Projektpartnern für ein Untersuchungsgebiet in Norddeutschland ein solches 3D Untergrundmodell entwickelt (Bremerhaven-Cuxhavener Rinne mit Informationen und Daten aus Strukturgeologie, Elektro-Magnetik, Gravimetrie, Seismik und Bohrungen). In dieser Arbeit wird gezeigt, wie die Modellgeometrie für die Schweremodellierung aufbereitet und mit Literatur-Dichten für die verschiedenen lithologischen Einheiten vervollständigt wurde. Der berechnete Modellschwereeffekt wird mit den Ergebnissen früherer Arbeiten verglichen.
Der Vergleich mit den residualen Schwerefeldern ergab eine weitgehende Übereinstimmung. Unterschiede werden damit begründet, dass Dichteänderungen innerhalb der oberflächennahen lithologischen Einheiten nicht im Modell abgebildet werden konnten. Später wird ein hier entwickeltes Verfahren zur statistischenAbschätzung unbekannter Verteilungen von Materialparametern imUntergrund abgeleitet und gezeigt, wie diese oberflächennahen Dichten abgeschätzt werden können.
Das Verfahren ermöglicht es, aus der vorhandenen Verteilung der spezifischen Widerstände für die Bremerhaven-Cuxhavener Rinne Aussagen über die relative Verteilung der Dichten im Modellgebiet zu treffen.
Der heutzutage übliche enorm große Datenumfang geophysikalischer Datensätzen erschwert die numerische Verarbeitung oft massiv. Es wird deshalb untersucht, wie Punktdatensätze und/oder triangulierte Netze so optimiert werden können, dass sie trotz erheblich reduziertem Datenumfang für geophysikalische Anwendungen bei der weiter verwendet werden können: CIDRe heißt das in dieser Arbeit entwickelte Verfahren, dass es erlaubt, die Punktmenge von Datensätze so zu reduzieren, dass in Regionen mit geringen Änderungen in den Datenparametern niedrigere Punktdichten erzielt werden als in Regionen mit sich stark änderndenWerten. Anwendungen basieren auf der Auswertung von Datensätzen der Satellitenaltimetrie vor Nord-Chile und Aero-Gradiometer-Messungen in Nord-Norwegen.
Auch eine enorm hohe Anzahl von Dreiecken in einem triangulierten Geometriemodell erschwert die Verwendung dieser Geometrie in der 3D Modellierung und bei der Visualisierung. Um die Dreiecksanzahl dieser Modelle zu reduzieren, werden Verfahren vorgestellt, die hoch aufgelöste triangulierte Modelle vereinfachen und dabei deren “Form” weitgehend erhalten. Hierzu wurden verschiedene Ansätze der “Mesh-Simplification” implementiert und an die Erfordernisse der Schwereberechnung angepasst.
Mit Hilfe dieser Verfahren wird ein sehr hoch aufgelöstes Modell zweier Salzstöcke im Gifhorner Trog, auf nur 5% der initialen Dreiecksanzahl reduziert, ohne dass die Güte der darauf basierenden Schweremodellierung beeinträchtigt wird; d.h. es werden nur Differenzen zwischen den berechneten Schwerefeldkomponenten und -gradienten für das Ausgangsmodell und die vereinfachten Modelle von 1% zugelassen.
3D-Druck ist ein inzwischen weit verbreitetes Mittel zur analogen Repräsentation digitaler 3D Modelle vor allem in der Industrie und den Ingenieurwissenschaften. Es wird untersucht, wie ein 3D-Druck für geophysikalische Anwendungen genutzt warden kann. Beispielhaft wird dies am 3D-Drucker “Ultimaker 2” gezeigt und beschrieben, wie verschiedene 2D und 3D Modelle aus der Gravimetrie für den 3D-Druck aufbereitet werden. Im Rahmen dieser Arbeit wird gezeigt, dass mit analogen Repräsentationen von geophysikalischen Ergebnissen ein hoher kommunikativer Mehrwert erzielt werden kann.
  • Doctoral thesis
    Christian-Albrechts-Universität zu Kiel, 2017
    Mentor: Prof. Dr. Hans-Jürgen Götze
    161 Seiten
  • Lecture (others)
    Disputation zur Dissertation, 12.09.2016, Kiel, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24740
Publ.-Id: 24740


Observation of large magnetocaloric effect in equiatomic binary compound ErZn

Li, L.; Yuan, Y.; Xu, C.; Qi, Y.; Zhou, S.
The magnetism, magnetocaloric effect and universal behaviour in rare earth Zinc binary compound of ErZn have been studied. The ErZn compound undergoes a second order paramagnetic (PM) to ferromagnetic (FM) transition at Curie temperature of T C ∼ 20 K. The ErZn compound exhibits a large reversible magnetocaloric effect (MCE) around its own T C. The rescaled magnetic entropy change curves overlap with each other under various magnetic field changes, further confirming the ErZn with the second order phase transition. For the magnetic field change of 0-7 T, the maximum values of the magnetic entropy change (−∆SMmax), relative cooling power (RCP) and refrigerant capacity (RC) for ErZn are 23.3 J/kg K, 581 J/kg and 437 J/kg, respectively.

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Permalink: https://www.hzdr.de/publications/Publ-24739
Publ.-Id: 24739


Example of High Power Laser Experiment: High-contrast laser-proton acceleration from condensed hydrogen jet

Zeil, K.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Brack, F.; Metzkes, J.; Kluge, T.; Kraft, S.; Sommer, P.; Loeser, M.; Ziegler, T.; Schramm, U.; Goede, S.; Wolter, S.; Kazak, L.; Gauthier, M.; Curry, C.; Macdonald, M.; Schumaker, W.; Mishra, R.; Ruyer, C.; Fiuza, F.; Roedel, C.; Glenzer, S.
The presentation gives an overview of a recent experiments for laser driven proton acceleration with high contrast using a plasma mirror at the high power laser Draco at HZDR, delivering pulses of 30fs and 3J on a cryogenic hydrogen target. Challenges of laser alignment and target preparation will be discussed in detail.
  • Invited lecture (Conferences)
    EUCALL Annual Meeting 2016, 01.09.2016, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24738
Publ.-Id: 24738


High-contrast laser-proton acceleration from condensed hydrogen jet

Zeil, K.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Brack, F.; Metzkes, J.; Kluge, T.; Kraft, S.; Sommer, P.; Loeser, M.; Ziegler, T.; Schramm, U.; Goede, S.; Wolter, S.; Kazak, L.; Gauthier, M.; Curry, C.; Macdonald, M.; Schumaker, W.; Mishra, R.; Ruyer, C.; Fiuza, F.; Roedel, C.; Glenzer, S.
Demanding applications like radiation therapy of cancer have pushed the development of laser plasma proton accelerators and defined levels of control and necessary proton beam stability in laser plasma experiments. The presentation will give an overview of the recent experiments for laser driven proton acceleration with high contrast using a plasma mirror at the high power laser Draco at HZDR, delivering pulses of 30fs and 3J on target. We present results of an experimental campaign employing a pure condensed hydrogen jet as a renewable target.
  • Lecture (Conference)
    Advanced Accelerator Conference 2016, 01.08.2016, National Harbor, Maryland, USA

Permalink: https://www.hzdr.de/publications/Publ-24737
Publ.-Id: 24737


New developments in Contactless Inductivee Flow Tomography

Ratajczak, M.; Gundrum, T.; Wondrak, T.; Martin, R.; Stefani, F.; (Editors)
The contactless inductive flow tomography (CIFT) is a measurement technique that allows for reconstructing the mean global flow of an electrically conducting fluid. This is done by applying a primary magnetic field, measuring the flow induced secondary field outside of the container and solving the underlying inverse problem. A promising candidate for the application of CIFT is the continuous casting of steel, where any means of online flow-monitoring could help improving the process and might as well give new insights to the processes in the casting mould. In this paper we will give an overview of the achievements in tailoring CIFT to models of continuous casting, being in particular (a) a two-phase flow in a slab-mould using Argon injection, (b) a mould with an electromagnetic stirrer around the submerged entry nozzle, and (c) the application to a mould influenced by a strong electromagnetic brake (talk only).
Keywords: contactless inductive flow tomography, continuous casting, two-phase flow, magnetic stirring
  • Lecture (Conference)
    Optimization and Inverse Problems in Electromagnetism, 13.-15.09.2016, Roma, Italia

Permalink: https://www.hzdr.de/publications/Publ-24736
Publ.-Id: 24736


Low-energy magnetic dipole radiation in open-shell nuclei

Schwengner, R.; Frauendorf, S.; Brown, B. A.
Low-energy M1 strength functions of 60,64,68Fe are determined on the basis of large-scale shell-model calculations with the goal to study their development from the bottom to the middle of the neutron shell. We find that the zero-energy spike, which characterizes nuclei near closed shells, develops toward the middle of the shell into a bimodal structure composed of a weaker zero-energy spike and a scissors-like resonance around 3 MeV, where the summed strengths of the two structures change within only 8% around a value of 9.8 nuclear magnetons. The summed strength of the scissors region exceeds the total absorption strength from the ground state by a factor of 2 or more, which explains the discrepancy between total strengths of the scissors resonance derived from (gamma,gamma') experiments and from experiments using light-ion induced reactions.
Keywords: Nuclear structure, shell model, strength functions, collectivity.

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Permalink: https://www.hzdr.de/publications/Publ-24735
Publ.-Id: 24735


Measurement of bubble parameters in opaque fluids using ultrasound transit time technique

Richter, T.; Wondrak, T.; Eckert, K.; Odenbach, S.
The mapping of the fluid flow and the detection of bubbles is very important for opaque fluids, like liquid metals. In these cases ultrasound techniques can be used. Especially the ultrasound transit time technique (UTTT) possesses advantages for studying the bubble distribution or the contour dynamics. In order to validate UTTT with standard optical methods, we started with experiments of single Argon bubbles rising in water. The trajectory, the diameter, the terminal velocity and the tilting of the bubbles were measured simultaneously with UTTT and with a high speed camera. The results of both measurements techniques showed a good agreement.
After these calibration measurements first experiments of Ar bubbles rising in GaInSn were performed. In these experiments the bubble behavior was investigated for different magnitudes of a DC magnetic field in horizontal direction. The parameters of the bubble as well as the velocity of the bubble and of the wake were recorded simultaneously by UTTT and Ultrasound Doppler Velocimetry (UDV), respectively. The results of these measurements were compared with independent measurements using X-ray radiography, which visualized the entire trajectory of the bubble without an applied magnetic field.
The results of the UTTT measurements are shown in Figure 1). The measured bubble position xB and bubble diameter dB of one bubble are shown without (left) and with an applied magnetic field of 500 mT (right). Without magnetic _eld the bubble shows a zig-zag trajectory with an amplitude larger than 4 mm and the measured bubble diameter alternates during the rise between values of 3.4 mm up to 4.9 mm, which is inflicted by the tilting of the bubble during the zig-zag rise. For an applied magnetic field of 500 mT is the bubble trajectory straightened and the diameters show regular behavior around 5.3 mm. The shapes of the diameter curves without applied field are more irregular, indicating the tilting of an ellipsoidal bubble. The diameter curves with 500 mT have a near parabolic shape, so we can assume that there is nearly no tilting. Independent x-ray measurements on the same vessel visualized also the zigzag rise and a tilting of the bubble. These results are in good agreement with the UTTT data.
  • Lecture (Conference)
    14th Multiphase Flow Workshop - Short Course and Conference, 08.-10.11.2016, Dresden, Deutschland

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Publ.-Id: 24734


Ion induced self-organized patterning of crystalline semiconductor surfaces

Facsko, S.ORC; Ou, X.; Engler, M.; Erb, D.; Hübner, R.; Škeren, T.
Low energy ion irradiation drives surfaces out of equilibrium by continuous atomic displacements in the sub-surface. At room temperature the accumulation of the created defects leads to surface amorphization and self-organized ripple patterns perpendicular or parallel to the ion beam direction are formed for incidence angles higher than 50°. At temperatures higher than the recrystallization temperature, however, all defects in the sub-surface region are dynamically annealed and the surface remains crystalline. In this regime, ion irradiation creates vacancies and ad-atoms on the crystalline surface due to sputtering and dislocations. The surfaces morphology is now determined by the kinetics of the mobile surface species. Due to the Ehrlich-Schwoebel barrier, i.e. an additional barrier for crossing terrace steps, 3D structures are created in a “reverse epitaxy” process [1].
We will present different kinds of self-organized patterns on crystalline surfaces induced by ion irradiation at elevated temperatures. Depending on the crystalline structure and the surface orientation regular patterns of inverse pyramids with three-fold, four-fold, or six-fold symmetry are observed. Furthermore, on III-V semiconductors with zinc-blende structure extremely regular periodic groove patterns with crystalline facets are produced [2].
Such periodic patterns can be used as templates for the deposition of nanostructured thin films with effective medium properties determined by the morphology, e.g. exhibiting a strong anisotropy.
[1] X. Ou, A. Keller, M. Helm, J. Fassbender, and S. Facsko, Phys. Rev. Lett. 111, 016101 (2013).
[2] X. Ou, K.-H. Heinig, R. Hübner, J. Grenzer, X. Wang, M. Helm, J. Fassbender, and S. Facsko, Nanoscale 7, 18928 (2015).
Keywords: nanopatterning, ion beam irradiation, reverse epitaxy
  • Lecture (Conference)
    E-MRS 2016 Fall Meeting, 19.-22.09.2016, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-24733
Publ.-Id: 24733


DREsden Accelerator Mass Spectrometry (DREAMS): Chemie lässt uns besser träumen!

Merchel, S.; Rugel, G.; Scharf, A.; Ziegenrücker, R.; DREAMS-Users; DREAMS-Friends
Die Methode der Wahl zur Bestimmung langlebiger Radionuklide (t1/2=ka-Ma) ist die Beschleunigermassenspektrometrie (accelerator mass spectrometry; AMS). Die AMS als massenspektrometrische Methode detektiert nicht den Zerfall der Nuklide, sondern als beschleunigte Ionen ähnlich anderer klassischer Ionenstrahlmethoden wie RBS/ERD. Allerdings befinden sich die Proben in der Cs-Sputterionenquelle, so dass eine effiziente negative Ionisierung der Probe absolut erforderlich ist.
Ein zweiter Unterschied ist die zwingend notwendige chemische Probenpräparation, da die Originalproben (H2O, Gestein, Meteorite, etc.), die ausreichende Gesamtmengen an Radionuklid enthalten, zu groß (100 mg-10 kg) sind. Oder anders formuliert, die Radionuklidkonzentrationen von sub-ppq sind zu gering, um die Analyse typischer 1 mg-AMS-Targets zu ermöglichen.
Zudem leistet die chemische Aufarbeitung den ersten wichtigen Schritt zur Isobarenunterdrückung und entfernt ggf. Radionnuklidkontaminationen anderen Ursprungs. So kann z.B. die Analyse des kosmogen gebildeten 10Be in Quarz nur erfolgen, nachdem die Proben von der um mehrere Größenordnungen höhere 10Be-Komponente - aus der Produktion in der Erdatmosphäre - befreit worden sind. Die AMS-Messung dauert nur ca. eine Stunde, wohingegen für die Probenaufbereitung Tage bis Wochen notwendig sind und diese somit ein wichtiges Forschungsfeld ist.
AMS-Anwendungen sind verschiedenartig und fast immer multidisziplinär. Die anfänglich bevorzugt untersuchten Proben aus der Kosmochemie, Astrophysik und für Kernreaktionsdaten, werden zunehmend von Proben aus den Bereichen Erde- und Umwelt, Strahlenschutz, Nuklearsicherheit, Nuklearentsorgung, Radioökologie, Phytologie, Ernährungswissenschaften, Toxikologie und Pharmakologie verdrängt. Am HZDR steht die AMS (inkl. dem Zugang zu dedizierten Chemielaboren) für Entwicklungen und die routinemäßige Bestimmung von 10Be, 26Al, 36Cl, 41Ca und 129I auch externen Nutzern kostenfrei zur Verfügung (Proposalsystem: www.hzdr.de/ibc).
Keywords: accelerator mass spectrometry, AMS, radionuclide
  • Poster
    Ionentreffen, 13.-15.02.2017, Göttingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24732
Publ.-Id: 24732


Properties of Metallic Thin Films Grown On Periodically Corrugated Surfaces

Facsko, S.ORC; Ou, X.; Engler, M.; Erb, D.; Lenz, K.
Nanostructured thin films are of growing relevance for all kind of applications in pho-tovoltaics, plasmonics, or as magnetic materials. Various methods have been used to fabricate nanostructured thin films with well defined morphology exhibiting tunable effective properties. Bottom-up, self-organized methods have been used extensively in the last years because of their fast and easy way of producing large-scale patterns with structures down to 10 nm.
Ion beam sputtering has proven to be a promising way to produce self-organized patterns on various surfaces [1]. Depending on the ion beam incidence angle, hex-agonally ordered dot patterns as well as ripple patterns oriented perpendicular or parallel to the ion beam direction are formed during the continuous sputtering. Peri-odically corrugated surfaces can also be obtained via crystal surface reconstruction during annealing. The resulting surfaces provide templates for the growth of nano-patterned thin films. Depending on the surface and interface free energies these films can grow in a conformal way reproducing the surface topography or as nano-particles on the substrate surface. Furthermore, depending on deposition angle, substrate temperature, beam flux, and deposition time, the nanoparticles can align parallel to the ripples, eventually coalescing and forming nanowires, thus tuning the physical properties of these structures via their geometrical dimensions.
Metal thin films grown in this way exhibit distinct optical properties due to localized surface plasmon resonance. Due to their alignment along the ripple structures the nanoparticles exhibit strongly anisotropic plasmonic resonances [2]. Furthermore, the magnetic properties of ferromagnetic thin films grown on rippled or faceted sub-strates are drastically changed by the presence of the periodic structures at the inter-face and on the surface [3].

[1] X. Ou, K.-H. Heinig, R. Hübner, J. Grenzer, X. Wang, M. Helm, J. Fassbender, and S. Facsko, Nanoscale 7, 18928 (2015).
[2] T.W.H. Oates, M. Ranjan, S. Facsko, and H. Arwin, Opt. Express 19, 2014 (2011).
[3] M.O. Liedke, M. Korner, K. Lenz, M. Fritzsche, M. Ranjan, A. Keller, E. Čižmár, S.A. Zvyagin, S. Facsko, K. Potzger, J. Lindner, and J. Fassbender, Phys. Rev. B 87, 024424 (2013).
Keywords: metallic thin films; magnetic properties; optical properties; surface plasmon resonance
  • Invited lecture (Conferences)
    18th International Conference on Solid Films and Surfaces (ICSFS18), 28.08.-2.09.2016, Chemnitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24731
Publ.-Id: 24731


Defect-induced magnetism in SiC probed by nuclear magnetic resonance

Zhang, Z.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Wang, Y.; Helm, M.; Zhou, S.; Kühne, H.
We give evidence for intrinsic, defect-induced bulk paramagnetism in SiC by means of 13 C and 29 Si nuclear magnetic resonance (NMR) spectroscopy. The temperature dependence of the internal dipole-field distribution, probed by the spin part of the NMR Knight shift and the spectral linewidth, follows a Curie law and scales very well with the macroscopic DC susceptibility. In order to quantitatively analyze the NMR spectra, a microscopic model based on dipole-dipole interactions was developed. The very good agreement between these simulations and the NMR data establishes a direct relation between the frequency distribution of the spectral intensity and the corresponding real-space volumes of nuclear spins. The presented approach by NMR can be applied to a variety of similar materials and, thus, opens a new avenue for the microscopic exploration and exploitation of diluted bulk magnetism in semiconductors.
Keywords: nuclear magnetic resonance; defect magnetism; SiC
  • Lecture (Conference)
    E-MRS (European Materials Research Society) 2016 Fall Meeting, 18.-22.09.2016, Warsaw University of Technology, Poland
  • Poster
    MEMRIOX International Workshop 2016, 25.-27.09.2016, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-24730
Publ.-Id: 24730


Ion Irradiation Assisted Fabrication of Si Quantum Dots for Ultra-Low Power Electronics

Heinig, K. H.; Facsko, S.; Stegemann, K. H.; Pruefer, T.; Xu, X.; Hlawacek, G.; Huebner, R.; Wolf, D.; Bischoff, L.; Moeller, W.; Borany, J.
The use of single electron transistors in large-scale integrated circuits promises a further boost for higher integration density and lower power consumption. However, in order to achieve single electron operation at room temperature, quantum dots (QDs) with a few nanometers in diameter and defined tunnel junctions have to be fabricated. A technological route to achieve such requirements is the fabrication of Si QDs embedded in SiO2 by phase separation of metastable SiOx (x<2).
In a CMOS-compatible manner, a Si rich oxide layer is produced by ion beam irradiation through a Si/SiO2/Si stack [1]. Choosing the right thickness of the oxide layer of ~7 nm leads to the formation of QDs in the middle of the layer [2]. The position of the Si QDs formed by the subsequent phase separation can be further controlled by applying geometrical constrains to the self-assembly process. This can be achieved in two ways. Firstly, the Si concentration in the SiO2 is strongly enhanced locally by focused ion beam induced mixing. Secondly, under broad beam irradiation of pillars consisting of Si/SiO2/Si stacks, the local mixing is defined by the pillar diameter. It is predicted by 3D kinetic Monte-Carlo (kMC) simulations that a single Si QD of few nm in diameter is formed in the middle of the SiO2 layer of the pillar structure. The optimal geometries and irradiation condition for fabricating reproducible QDs are explored by means of 3DkMC using input data from dynamic 3D ion collision simulations (TRI3DYN).
We will discuss the underlying principles and the mechanism of Si QD formation by ion induced directed self-assembly and present first results of focused Ne+ ion irradiations of a Si/SiO2/Si layer stack as well as Si+ broad beam irradiations of pillars.
This work is part of the project IONS4SET (Horizon 2020 research and innovation program, Grant Agreement No 688072).
[1] K.-H. Heinig et al., Appl. Phys. A77, 17 (2003).
[2] L. Röntzsch et al., phys. stat. sol.(a) 202, R170(2005).
Keywords: ion irradiation, single electron transistor, Si quantum dots
  • Invited lecture (Conferences)
    20th International Conference on Ion Beam Modification of Materials (IBMM 2016), 30.10.-4.11.2016, Wellington, New Zealand

Permalink: https://www.hzdr.de/publications/Publ-24729
Publ.-Id: 24729


Die Anwendung von Level-Of-Detail und Mesh-Simplification Strategien zur Vereinfachung komplexer Untergrundmodelle

Menzel, P.; Alvers, M.; Barrio-Alvers, L.; Götze, H.-J.; Schmidt, S.; Plonka, C.
Die Interpretation von moderner 2D und 3D Seismik ermöglicht die Abbildung von Untergrundstrukturen mit sehr hoher Auflösung und Genauigkeit. Der große Datenumfang der auf der Grundlage von Messungen kompilierten Strukturmodelle erschwert of deren weitere Verwendung in anderen Modellierverfahren in den Geowissenschaften. Deshalb muss für diese Verfahren evaluiert werden, ob die gegebene geometrische Modellauflösung angemessen ist oder ob sie reduziert werden kann.
Komplexe Untergrundmodelle bestehen häufig aus mehreren komplexen triangulierten Flächen.
Um Anzahl der Dreiecke möglichst informationserhaltend zu reduzieren, werden in diesem Beitrag verschiedene hierarchische Ansätze verwendet und die Ergebnisse bezüglich ihrer Anwendbarkeit für eine Potenzialfeldvorwärtsmodellierung validiert. Die verwendeten Verfahren vereinfachen Dreiecksgitter, indem sukzessive Geometrieelemente aus einer gegebenen Vermaschung entfernt werden. Die Reihenfolge, in der die Elemente entfernt werden, wird dabei durch verschiedene Gewichtungsstrategien bestimmt. Alle verwendeten Verfahren erstellen hierarchische Strukturen, welche es ermöglichen, eine Modellgeometrie kontinuierlich in verschiedenen Auflösungsstufen („Level-Of-Detail“) bereit zu stellen und diese ineinander zu überführen.
Die Anwendung der „Mesh-Simplification“ Ansätze wird sowohl an synthetischen als auch an realen Geometriemodellen demonstriert. Für jedes Modell wurden verschiedenen Varianten der Modellgeometrie in mehreren Auflösungsstufen erzeugt. Sowohl für die niedriger aufgelösten Geometrien als auch für die initialen Modelle werden anschließend der Schwereeffekt und die Schweregradienten mit unserer hauseigenen Modelliersoftware IGMAS+ berechnet und miteinander verglichen.
Es wird gezeigt, dass die initiale Auflösung der gegebenen Modellgeometrie für die Berechnung des Schwere- und Schweregradienteneffektes bezüglich der Genauigkeit der vorhandenen Messdaten häufig nicht notwendig ist. Auch für vergleichsweise niedrig aufgelöste Modellversionen lässt sich ein FTG („full tensor gravity“)-Effekt berechnen, welcher sich kaum vom Effekt des initialen Modells unterscheidet, aber aufgrund der geringeren Dreiecksanzahl sehr viel effizienter berechnet werden kann. Dies gilt insbesondere für die Ergebnisse der „Mesh-Simplification“ Strategien, welche zusätzlich die Positionen der vorhandenen Schweremessungen für die Evaluation der Reihenfolge der Dreiecksgittervereinfachung mit heranziehen.
Keywords: Potentialfeldmodellierung, 3D Visualisierung, 3D Geometrie
  • Lecture (Conference)
    76. Jahrestagung der Deutschen Geophysikalischen Gesellschaft e.V., 14.-17.03.2016, Münster, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24728
Publ.-Id: 24728


Purely Antiferromagnetic Magnetoelectric Random Access Memory

Kosub, T.; Kopte, M.; Hübner, R.; Liedke, M.; Lindner, J.; Fassbender, J.ORC; Makarov, D.; Hühne, R.; Schmidt, O. G.; Appel, P.; Shields, B.; Maletinsky, P.
Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy efficiency. We propose and demonstrate a purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50 fold reduction of the writing threshold compared to ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we demonstrate reliable isothermal switching via gate voltage pulses and all-electric readout at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed for readout, allowing permanent magnets to be used.
Based on our prototypes of these novel AF-MERAM elements, we construct a comprehensive model of the magnetoelectric selection mechanism in thin films of magnetoelectric antiferromagnets. We identify that growth induced effects lead to emergent ferrimagnetism, which is detrimental to the robustness of the storage. After pinpointing lattice misfit as the likely origin, we provide routes to enhance or mitigate this emergent ferrimagnetism as desired.
Beyond memory applications, the AF-MERAM concept introduces a general all-electric interface for antiferromagnets and should find wide applicability in purely antiferromagnetic spintronics devices. In particular, the read out of the magnetic state is realized by Zero-Offset Hall [Kosub et al., Phys. Rev. Lett. 115, 097201 (2015)] which can detect the proximity magnetization that developes in metallic electrodes at the boundary of insulating antiferromagnets. This technique possesses considerable applicability to the field of antiferromagnetic spintronics, as it can probe the net magnetization of both metallic and insulating antiferromagnetic thin films.
  • Poster
    SPICE Workshop on Antiferromagnetic Spintronics, 26.-30.09.2016, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24727
Publ.-Id: 24727


1-D Fe-rich Konbu phase in InAs obtained by Fe ion implantation and pulsed laser melting

Yuan, Y.; Sawicki, M.; Hübner, R.; Potzger, K.; Weschke, E.; Dietl, T.; Helm, M.; Zhou, S.
Transition-metal rich semiconductor nanostructures driven by spinodal decomposition are drawing considerable attention due to wide prospects of functionalization [1]. However, the complexity of the magnetic cations aggregation (e.g. the competition between p-d hybridization driven attractive force between magnetic cation, entropy terms, and kinetic barriers) hinders obtaining nano-clusters with the desirable structure. Here, a 1-dimensional (In,Fe)As mixed Konbu phase is tailoring by employing ion implantation and subsequent pulsed laser melting (shown in Fig. 1). These Fe-rich nano-columns are fully commensurate with the InAs host lattice and exhibit an isotropic super-paramagnetic behavior. The XAS/XMCD result shows that Fe atoms with valence +2 and +3 are co-existing and both are spin-polarized. Therefore, it is likely that the magnetism in these Fe-rich nano-columns can be provided via the double exchange mechanism as previously described for the Cr-rich phase in (Zn, Cr)Te [2]. However, it still remains to be clarified why these distinctive structures are formed only in InAs: Fe, but not in other III-Mn-V systems obtained by the same method.

[1]. T. Dietl, et al., Rev. Mod. Phys., 87, 1311-1377 (2015)
[2]. K. Kanazawa, et al., Nanoscale, 6, 14667-14673 (2014)
  • Poster
    Jaszowiec 2016, 20.-24.06.2016, Szczyrk, Poland

Permalink: https://www.hzdr.de/publications/Publ-24726
Publ.-Id: 24726


Bioflotation with Siderophores

Schrader, S.ORC
Siderophores are small organic molecules with a high affinity for binding Fe(III) and the ability to form strong complexes. They are produced by microorganisms to equalize the low bioavailability of iron in their environment.
There already is wide knowledge about siderophores, their different structures and the microorganisms (aerobic bacteria and fungi), that produce them.
The aim of the study is to test for the first time, whether it is possible to use siderophores for flotation processes.
Molecules with similar functional groups from the chemical industry have been applied successfully in flotation processes. The main advantage of using biotechnology for the production of siderophores is the wide natural diversity of the structures.
Keywords: siderophore, flotation, hydroxamates
  • Lecture (others)
    Microbiology Meeting HZDR - TU Bergakademie Freiberg, 07.11.2016, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24725
Publ.-Id: 24725


Production of 2-hydroxyisobutyric acid from methanol by Methylobacterium extorquens AM1 expressing (R)-3-hydroxybutyryl-CoA isomerizing enzymes

Rohde, M.-T.ORC; Tischer, S.ORC; Harms, H.ORC; Rohwerder, T.
The biotechnological production of the methyl methacrylate precursor 2-hydroxyisobutyric acid (2-HIBA) via bacterial poly-3-hydroxybutyrate (PHB) overflow metabolism requires suitable (R)-3-hydroxybutyryl-CoA specific coenzyme B12-dependent mutases (RCM). Here, we characterized a predicted mutase from Bacillus massiliosenegalensis JC6 as a mesophilic RCM, closely related to the thermophilic enzyme previously identified in Kyrpidia tusciae DSM 2912 (M.-T. Weichler, N. Kurteva-Yaneva, D. Przybylski, J. Schuster, R. H. Müller, H. Harms, and T. Rohwerder, Appl Environ Microbiol 81:4564-4572, 2015, http://dx.doi.org/10.1128/AEM.00716-15). Using both RCM variants, 2-HIBA production from methanol was studied in fed-batch bioreactor experiments with recombinant Methylobacterium extorquens AM1. After complete nitrogen consumption, concomitant formation of PHB and 2-HIBA was achieved, indicating that both sets of RCM genes were successfully expressed. However, although identical vector systems and incubation conditions were chosen, metabolic activity of the variant bearing the RCM genes from strain DSM 2912 was severely inhibited, likely due to negative effects caused by the heterologous expression. In contrast, biomass yield of the variant expressing the JC6 genes was close to wild-type performance and 2-HIBA titers of 2.1 g L-1 could be demonstrated. In this case, up to 24% of the substrate channeled into overflow metabolism was converted to the mutase product and maximal combined 2-HIBA plus PHB yields from methanol of 0.11 g g-1 were achieved. Reverse transcription-quantitative PCR analysis revealed that metabolic genes, such as methanol dehydrogenase and acetoacetyl-CoA reductase genes, are strongly down-regulated after exponential growth which currently prevents a prolonged overflow phase and, thus, higher product yields with strain AM1.
Keywords: bulk chemicals, fed-batch bioreactor, overflow metabolism, polyhydroxybutyrate, acyl-CoA mutase

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Permalink: https://www.hzdr.de/publications/Publ-24723
Publ.-Id: 24723


Constrained indicator data resampling — A parameter constrained irregular resampling method for scattered point data

Menzel, P.
Resampling of high-resolution data sets is often required for real-time applications in geosciences, e.g., interactive modeling and 3D visualization. To support interactivity and real-time computations, it is often necessary to resample the data sets to a resolution adequate to the application. Conventional resampling approaches create uniformly distributed results, which are not always the best possible solution for particular applications. I have developed a new resampling method called constrained indicator data resampling (CIDRe). This method results in irregular point distributions that are adapted to local parameter signal wavelengths of the given data. The algorithm identifies wavelength variations by analyzing gradients in the given parameter distribution. A higher point density is ensured in areas with larger gradients than in areas with smaller gradients, and thus the resulting data set shows an irregular point distribution. A synthetic data test showed that CIDRe is able to represent a data set better than conventional resampling algorithms. In a second application, CIDRe was used to reduce the number of gravity stations for interactive 3D density modeling, in which the resulting point distribution still allows accurate interactive modeling with a minimum number of data points.
Keywords: resampling, potential field modelling, data reduction

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Permalink: https://www.hzdr.de/publications/Publ-24722
Publ.-Id: 24722


Bioflotation mit Siderophoren

Schrader, S.ORC; Kutschke, S.ORC; Pollmann, K.; Rudolph, M.ORC
Siderophoren stellen organische Verbindungen niedrigen Molekulargewichts dar, die eine hohe Affinität zur selektiven Komplexierung von Eisen(III)-Ionen aufweisen. Mikroorganismen, wie aerobe Bakterien oder Pilze, bilden diese Moleküle, um die geringe Bioverfügbarkeit des in der Natur vorkommenden Eisens zu kompensieren.
Mit Hilfe der biotechnologischen Herstellung von Siderophoren besteht die Möglichkeit, diese in unterschiedlichen Anwendungsgebieten zu nutzen. Neben dem medizinischen Einsatz zur Behandlung übermäßiger Eisenaufnahme und Schwermetallvergiftungen, liegt eine weitere Applikation in der (Rück)-Gewinnung des Rohstoffes Eisen, sowie anderer Metalle, die gleichermaßen durch Siderophoren gebunden werden können. Ein weiteres potenzielles Anwendungsgebiet ist ihr Einsatz in Flotationsprozessen. Der Vorteil in der Verwendung biotechnologisch hergestellter Siderophoren liegt in der strukturellen Vielfalt, die diese aufweisen. So sind u.a. Hydroxamate als chelatisierende Gruppen weit verbreitet und finden umgekehrt als Kollektoren in zahlreichen Flotationsprozessen Anwendung. Siderophoren sollten daher ebenfalls als Kollektoren wirken können. Vor allem die Klasse der amphiphilen Siderophoren, die sowohl einen hydrophoben, als auch hydrophilen Bereich besitzen, ist von großem Interesse. Die damit verbundene natürliche Hydrophobie der Moleküle könnte den häufig notwendigen und zusätzlichen Schritt der Hydrophobierung der Mineralpartikel in Flotationsprozessen unnötig machen.
Da bereits eine Vielzahl von Mikroorganismen und den von ihnen produzierten Siderophoren identifiziert und auch strukturell analysiert wurden, existiert ein großes Potenzial möglicher Liganden, welche im Prozess der Flotation Anwendung finden könnten. Neben dem Nachweis der prinzipiellen Eignung von Siderophoren als Flotationsreagenz, besteht allerdings noch die Notwendigkeit der Optimierung sowohl der biotechnologischen Produktion, als auch des Flotationsprozesses, sowie der genaueren Untersuchung und Charakterisierung der Bindungseigenschaften innerhalb dieses Verfahrens.
Keywords: Siderophoren, Hydroxamate, Flotation
  • Poster
    Tagung 2016 „Aufbereitung und Recycling“, 09.-10.11.2016, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24721
Publ.-Id: 24721


Experimentelle Untersuchung der Chemisorption von CO2 in NaOH und Kopplung zur Hydrodynamik von Blasenströmungen

Gustke, M.
Die vorliegende Arbeit beschäftigt sich mit der Ermittlung lokaler Informationen zum Vermischungsverhalten in einer reaktiven Blasensäule. Die Gittersensortechnik dient dabei als Messtechnik zur Quantifizierung des Reaktionsfortschrittes bei der Chemisorption von CO2 in NaOH-Lösung. Der im Vordergrund stehende Verbrauch der Hydroxid-Ionen wird, in Abhängigkeit des CO2-Durchsatzes und der NaOH-Startkonzentration, untersucht. Durch den Einsatz mehrerer querschnittsauflösender Gittersensoren können zahlreiche radiale und axiale Abhängigkeiten des Hydroxid-Ionen-Verbrauchs festgestellt werden. Die experimentell gewonnenen Erkenntnisse können mithilfe von mathematischen Modellen, auf Basis von Zellenmodell und axialem Dispersionsmodell, verglichen werden.
  • Diploma thesis
    TU Dresden, 2016
    Mentor: Ragna Kipping
    83 Seiten

Permalink: https://www.hzdr.de/publications/Publ-24720
Publ.-Id: 24720


Application of wire-mesh sensor for the study of chemical species conversion in a bubble column during chemical absorption of carbon dioxide in sodium hydroxide

Kipping, R.; Kryk, H.; Schleicher, E.; Gustke, M.; Hampel, U.
In this paper we report for the first time on the utilization of the wire-mesh sensor for the measurement of chemical species conversion during the chemical absorption of carbon dioxide in sodium hydroxide solution. The wire mesh-sensor obtains cross-sectional images of the liquid phase conductivity which changes with the conversion of hydroxides during the reaction. A theoretical model has been applied to verify the use of conductivity as indicator for the reaction progress. Demonstration experiments have been carried out in a lab-scale bubble column reactor using two wire-mesh sensors in different reactor heights. Results obtained from reactor model and experimental data show a very good agreement. The results demonstrate the potential of this imaging instrument to follow the course of a chemical reaction via ionic species concentration even in a dense bubbly flow. This way, a better understanding of the coupling of hydrodynamics, mass transfer and reaction in bubble columns and other reaction devices can be gained.
Keywords: chemical absorption, reactive two-phase flow, species concentration measurement, wire-mesh sensor

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Permalink: https://www.hzdr.de/publications/Publ-24719
Publ.-Id: 24719


Simulation of Condensation in a slightly inclined tube at COSMEA facility with ATHLET code

Zhang, Y.; Hampel, U.ORC; Geißler, T.; Leyer, S.
Safety is an essential topic in the development process of nuclear power plant. Several Generation III reactor designs contain passive safety system to control accident without the need for external power supply. An example for such passive systems is the Emergency Condenser (EC) of the KERENA reactor design. The system removes heat from the Reactor Pressure Vessel in the case of design basis accidents. The experimental facility COSMEA at Helmhotz Zentrum Dresden Rossendorf (HZDR) was set up to investigate the flow morphology and heat transfer structure of condensation processes. The test rig consists of a 3 m long condenser pipe whichpipe that is 0.76° inclined with inner diameter 43.3 mm. On the shell side active cooling is performed using the TOPFLOW facility infrastructure. According to the Emergency Condenser Reference design, the experiments of COSMEA are conducted in different pressure levels (5, 15, 25, 45 and 65 bar) with steam mass flow rates up to 1 kg/s. An inlet mixing system was developed to operate the experiment in a stepwise method due to the scale of the test rig. Condensation rates, pressure, temperature and flow rate for different steam fraction are measured. In addition, an x-ray tomography is installed to study the details of the resulting stratified flow structures. Extra heat flux probes are assembled to detect the azimuthal distribution of the heat flux. In this work, COSMEA was simulated with the thermal hydraulic system codes ATHLET. The performance of the ATHLET heat transfer models wereas identified. Primarily, the steady-state model was developed and the simulation results were compared to the experiment. The thermal coupling which considers the heat exchange between outside and inside of the pipe during the condensation was analyzed. Posteriorly the case of modeling transient condensation process was simulated. The influence on thermal coupling parameters, particularly heat transfer coefficient due to pressure drop inside the pipe was predicted and the feasibility and limitation of the system codes were evaluated.
Keywords: COSMEA, TOPFLOW, condensation, high pressure, ATHLET
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-8.9.17, Xi'an, Shaanxi, China
    Proceedings of NURETH-17

Permalink: https://www.hzdr.de/publications/Publ-24718
Publ.-Id: 24718


Suppressed Fat Appetite after Roux-en-Y Gastric Bypass Surgery Associates with Reduced Brain µ-opioid Receptor Availability in Diet-Induced Obese Male Rats

Hankir, M.; Patt, M.; Patt, J.; Becker, G.; Rullmann, M.; Kranz, M.; Deuther-Conrad, W.; Schichke, K.; Seyfried, F.; Brust, P.; Hesse, S.; Sabri, O.; Krügel, U.; Fenske, W.
Brain µ-opioid receptors (MORs) stimulate high-fat (HF) feeding and have been implicated in the distinct long term outcomes on body weight of bariatric surgery and dieting. Whether alterations in fat appetite specifically following these disparate weight loss interventions relate to changes in brain MOR signaling is unknown. To address this issue, diet-induced obese male rats underwent either Roux-en-Y gastric bypass (RYGB) or sham surgeries. Postoperatively, animals were placed on a two-choice diet consisting of low-fat (LF) and HF food and sham-operated rats were further split into ad libitum fed (Sham-LF/HF) and body weight-matched (Sham-BWM) to RYGB groups.
An additional set of sham-operated rats always only on a LF diet (Sham-LF) served as lean controls, making four experimental groups in total. Corresponding to a stage of weight loss maintenance for RYGB rats, two-bottle fat preference tests in conjunction with small-animal positron emission tomography (PET) imaging studies with the selective MOR radioligand [11 C]carfentanil were performed. Brains were subsequently collected and MOR protein levels in the hypothalamus, striatum, prefrontal cortex and orbitofrontal cortex were analyzed by Western Blot. We found that only the RYGB group presented with intervention-specific changes: having markedly suppressed intake and preference for high concentration fat emulsions, a widespread reduction in [11 C]carfentanil binding potential (reflecting MOR availability) in various brain regions, and a downregulation of striatal and prefrontal MOR protein levels compared to the remaining groups. These findings suggest that the suppressed fat appetite caused by RYGB surgery is due to reduced brain MOR signaling, which may contribute to sustained weight loss unlike the case for dieting.
Keywords: bariatric surgery, caloric-restriction, fat appetite, Brain µ-opioid receptors, positron emission Q13, tomography imaging

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Permalink: https://www.hzdr.de/publications/Publ-24717
Publ.-Id: 24717


Structures of Plutonium(IV) and Uranium(VI) with N,N‑Dialkyl Amides from Crystallography, X‑ray Absorption Spectra, and Theoretical Calculations

Acher, E.; Cherkaski, Y. H.; Dumas, T.; Tamin, C.; Guillaumont, D.; Boubals, N.; Javierre, G.; Hennig, C.; Solari, P. L.; Charbonnel, M.-C.
The structures of plutonium(IV) and uranium(VI) ions with a series of N,N-dialkyl amides ligands with linear and branched alkyl chains were elucidated from single-crystal X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and theoretical calculations. In the field of nuclear fuel reprocessing, N,N-dialkyl amides are alternative organic ligands to achieve the separation of uranium(VI) and plutonium(IV) from highly concentrated nitric acid solution. EXAFS analysis combined with XRD shows that the coordination structure of U(VI) is identical in the solution and in the solid state and is independent of the alkyl chain: two amide ligands and four bidentate nitrate ions coordinate the uranyl ion. With linear alkyl chain amides, Pu(IV) also adopt identical structures in the solid state and in solution with two amides and four bidentate nitrate ions. With branched alkyl chain amides, the coordination structure of Pu(IV) was more difficult to establish unambiguously from EXAFS. Density functional theory (DFT) calculations were consequently performed on a series of structures with different coordination modes. Structural parameters and Debye−Waller factors derived from the DFT calculations were used to compute EXAFS spectra without using fitting parameters. By using this methodology, it was possible to show that the branched alkyl chain amides form partly outer-sphere complexes with protonated ligands hydrogen bonded to nitrate ions.
Keywords: Pu(IV), U(VI), XRD, EXAFS, DFT

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Permalink: https://www.hzdr.de/publications/Publ-24716
Publ.-Id: 24716


3D potential field modelling and 3D prints of complex geological structures

Götze, H.-J.; Schmidt, S.; Menzel, P.
The new techniques used here are user-friendly because they are highly interactive, ideally real-time and topology conserving and can be used for both flat and spherical models in 3D. These are important requirements for joint inversion not only for gravity and magnetic modelling of fields and derivatives, constrained by seismic and structural input from independent data sources, but also essential toward a true integration of Full Waveform Inversion. A borehole tool for magnetic and gravity modelling will also be introduced. We are close to the demand of treating several geophysical methods in a single model for the subsurface and aim for fulfilling most of the constraints: measurements and geological plausibility.
For 3D modelling, polyhedrons built by triangles are used. All elements of the gravity and magnetic tensors can be included. In the modelling interface, after geometry changes the effect of the model can quickly be updated because only the changed triangles have to be recalculated. Because of the triangular model structure our approach can handle complex structures very well (e.g. overhangs of salt domes). For regional models the use of spherical geometries and calculations can be necessary and is provided. 3D visualization is performed with a 3D-printer (Ultimaker 2) and provides new insights in even rather complicate Earth subsurface structures.
Inversion can either be run over the whole model, but typically it is used in smaller parts of the model, helping to solve local problems and/or proving/disproving local hypotheses. Instead of optimizing the position of model vertices, interactive inversion uses a different parameterization of the model. The inner points of a lattice are used to define a distortion of space. The user can monitor model updates live on screen and stop the process at any time. The base principles behind this interactive approach are highly performance optimized algorithms (CMA-ES: Covariance-matrix-adoption-evolution-strategy). The efficiency of the algorithm is very good in terms of stable convergence due to topological model validity.
Potential field modelling is always influenced by the area outside the core area of investigation, causing edge effects. To avoid these effects a simple but very robust method has been developed: Derive a density/susceptibility-depth function by taking the mean value of the borders of depth slices through the model. The focus of the poster presentation is set on practical examples from the international KTB – Project, Germany´s deep continental borehole.
Keywords: geophysics, interactive 3D potential field modeling, 3D visualization
  • Poster
    77. Jahrestagung der Deutschen Geophysikalischen Gesellschaft e.V., Potsdam, 27.-30.03.2017, Potsdam, Deutschland
  • Lecture (Conference)
    DGMK/ÖEGW Frühjahrstagung 2017, 05.-06.04.2017, Celle, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24715
Publ.-Id: 24715


Local Lorentz force flowmeter at a continuous caster model using a new generation multicomponent force and torque sensor

Hernandez, D.; Schleichert, J.; Karcher, C.; Fröhlich, T.; Wondrak, T.; Timmel, K.
Lorentz force velocimetry is a non-invasive velocity measurement technique for electrical conductive liquids like molten steel. In this technique, the metal flow interacts with a static magnetic field generating eddy currents which, in turn, produce flow-braking Lorentz forces within the fluid. These forces are proportional to the electrical conductivity and to the velocity of the melt. Due to Newton’s third law, a counter force of the same magnitude acts on the source of the applied static magnetic field which is in our case a permanent magnet. In this paper we will present a new multicomponent sensor for the local Lorentz force flowmeter (L2F2) which is able to measure simultaneously all three components of the force as well as all three components of the torque. Therefore, this new sensor is capable of accessing all three velocity components at the same time in the region near the wall. In order to demonstrate the potential of this new sensor, it is used to identify the 3-dimensional velocity field near the wide face of the mold of a continuous caster model available at the Helmholtz-Zentrum Dresden-Rossendorf. As model melt, the eutectic alloy GaInSn is used.
Keywords: liquid metals, magnetohydrodynamics, Lorentz force, flow measurement

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Permalink: https://www.hzdr.de/publications/Publ-24714
Publ.-Id: 24714


Sustainable high magnetic field Research in Europe - EMFL AISBL

Wosnitza, J.
es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    Workshop on the sustainability of Laserlab-Europe, 11.10.2016, Amsterdam, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-24713
Publ.-Id: 24713


The FFLO state in quasi-two-dimensional organic superconductors

Wosnitza, J.
es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    14th Bilateral Japanese-German Symposium "Effects of Parity Mixing in Correlated Electron Systems", 26.-29.09.2016, Sapporo, Japan

Permalink: https://www.hzdr.de/publications/Publ-24712
Publ.-Id: 24712


Magnetic quantum oscillations - From simple metals to Weyl semimetals

Wosnitza, J.
es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    Summer School of SFB 1143, 19.-20.09.2016, Kloster Nimbschen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24711
Publ.-Id: 24711


The ternary sorption system U(VI)/ phosphate/SiO2: a consistent surface speciation derived from a multimethodological approach

Foerstendorf, H.ORC; Comarmond, M. J.; Heim, K.; Steudtner, R.; Stockmann, M.; Payne, T. E.
The surface speciation of the ternary system containing aqueous U(VI), phosphate and the model mineral phase SiO2 was comprehensively investigated at a low micromolar concentration level by batch experiments, in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR), luminescence spectroscopy, and Surface Complexation Modeling (SCM). In the absence of phosphate, two predominant U(VI) surface species were independently identified by luminescence and in situ IR spectroscopy. The concordance of the two species is corroborated by the shifts of the signals which were found to be of same extent in terms of energy units in the spectra of both spectroscopic techniques.
In the presence of phosphate, batch sorption studies indicate an increase in U(VI) uptake, consistent with previously reported studies. In situ IR spectroscopic sorption experiments strongly suggest the formation of a solid U(VI) phosphate phase as a surface precipitate on the silica phase, evidenced by characteristic bands observed in spectra after prolonged sorption and following sequential sorption of U(VI) then phosphate. Again, the results obtained from luminescence spectroscopy support these findings.
SCM provides excellent fitting results only when exclusively considering two binary uranyl surface species and formation of a solid uranyl phosphate phase as suggested from spectroscopic results. The results of this study indicate that the sorption of U(VI) on SiO2 in the presence of inorganic phosphate initially involves binary surface-sorption species and then evolves towards surface precipitation.
  • Lecture (Conference)
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-24710
Publ.-Id: 24710


Atomic force microscopy – A variable tool to characterize processes in the field of particle technology

Fritzsche, J.ORC; Peuker, U. A.ORC; Babel, B.; Rudolph, M.ORC
The paper aims at giving an overview on strategies and methods applying atomic force microscopy (AFM) in various particle based processes. AFM has a wide range of applications in the field of particle technology. The typical application of the AFM is the characterization of the surface topography in the submicron range. Using the AFM in combination with the colloidal probe technique allows furthermore the direct measurement of forces acting on a particle down to atomic interactions. This enables the study of several fundamental effects on these forces.
When a liquid cell is used, the direct measurement of forces between particles surrounded by a liquid can be studied. This allows the investigation of electrostatic as well as hydrophobic and hydrophilic interactions which superimpose the van der Waals forces in liquid media. It is also possible to determine the forces acting on particles at fluid interfaces (liquid/liquid or liquid/gas) which is quite important for research e.g. in flotation or particle extraction applications.
Especially in hydrophobic systems capillary bridges due to nano-bubbles (generally gas layers) on the surfaces can occur. This bridging can be seen as an additional strong adhesive interaction mechanism leading to forces which can be orders of magnitude higher than for pure van der Waals or classic hydrophobic interactions.
The detection of nano-bubbles is possible using a combination of topography and phasecontrast scans in non-contact mode. This allows the distinction between gas and solid phases during the surface scanning. On smooth surfaces, phase contrast AFM also allows a distinction between two different solid phases, e.g. in a nano-composite material. Furthermore the combination of AFM with Raman spectroscopy superimposes the measurements of mechanical forces, topographies and detailed chemical spectral characterization. With this method local surface modification can be identified. A proper choice of tip material of the AFM (noble metal nanostructures) can even lead to the so called tip enhanced Raman spectroscopy (TERS) enabling detection of vibrational signals from a small number of molecules on a solid surface, e.g. collector molecules on mineral surfaces for flotation applications.
  • Lecture (Conference)
    Partec 2016 - International Congress on Particle Technology, 19.-21.04.2016, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24709
Publ.-Id: 24709


Surface Energy Heterogeneities and Hydrophobic Interactions - New Insights to understand Flotation

Rudolph, M.ORC
Flotation is a heterocoagulation separation process first described in 1877 by a patent issued in Dresden, Germany. Since then it has become to be the most important and most variable separation process in the beneficiation of minerals. Especially the modern fine grained and polymetallic deposits call for a continuation in process development and even more so in better understanding the flotation process which is based on the selective hydrophobization/hydrophilization of minerals. This paper will present novel insights on the hydrophobization of various mineral particles, i.e. silicates, semi-soluble salt type minerals, metal oxides and sulfides with different collector molecules, which are the surfactants used to selectively hydrophobize minerals in flotation. We investigate the effect of the collectors on the surface energy distribution which is determined with inverse gas chromatography. With this method it is possible to assess the wettability of particles without the difficulties encountered with the conventional sessile drop and penetration methods. By applying inverse gas chromatography we can show that it is due to the collector adsorption the reduction of the highly energetic moieties which only make up less than ten percent of the particle surface. Furthermore we can present the effect of collector adsorption on the different surface energy components, i.e. disperse and specific interactions. By calculating the free energy of interaction between a particle and a bubble immersed in water using the complex surface energy information we can find a good correlation to the flotation response, i.e. recovery determined with classic microflotation experiments in the Hallimond tube. Further insight into the surface heterogeneity regarding the wettability is presented with respect to investigations on planarized mineral samples using the colloidal probe technique in atomic force microscopy in the liquid environment. By assessing force distance spectra on various surface sites with and without the adsorption of collectors we find the well described but so far not well understood long range attractive hydrophobic interactions. Based on the results presented we will critically discuss the different concepts of long range hydrophobic interactions in the context of a fundamental model which describes the floatability of minerals. The minerals used are: quartz, apatite, magnetite and pyrite. The collectors assessed are cationic and different anionic surfactants.
  • Lecture (Conference)
    Partec 2016 - International Congress on Particle Technology, 19.-21.04.2016, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24708
Publ.-Id: 24708


Floatability of synthetic light and heavy rare earth element carbonates and selectivity towards calcite

Rudolph, M.ORC; Kratzsch, R.
The fourteen lanthanoid elements, also commonly referred to as rare earth elements (REE) or rare earth metals (REM) and often including lanthanum as well as both Yttrium and Scandium, can be referred to as the vitamins of the periodic systems table. They are used for green and high tech applications such as powerful magnets, batteries, glasses and triband dyes. Commonly they can be found and mined as carbonate minerals, e.g. bastnäsite, synchisite and ankylite or as phosphate minerals, e.g. monazite and xenotim. Usually they all occur as mixed REM carbonates with different proportions of light and heavy rare earth elements. The light rare earth elements LREE (lanthanum through samarium) are less scarce and thus economically becoming less critical (EU list of critical elements from 2014). The heavy rare earths HREE (europium through lutetium plus yttrium) are indeed rare, scarce and thus considered critical elements. The ratio of LREE and HREE depends very much on the deposits. When beneficiating rare earth carbonate minerals flotation is often an important unit process operation especially to reduce content of silicates, calcite and barite. As flotation reagents in principle simple carboxylic acid type collectors are used in combination with silicate and calcite depressants. It has been reported (Nature (2013), 12, 315) that the surface wettability of REE oxides very much is influenced by high ionic radius of the REE cations. The ionic radius is indeed one of the distinguishable properties of the REE amongst one another. Therefore the question is how different synthetic unmixed individual LREE and HREE carbonates behave in terms of floatability.
Results are presented for the REE carbonates of yttrium, lanthanum, cer, neodymium, dysprosium and ytterbium with sodium oleate at different pH values. Lignin sulfonate is investigated as the selective depressant for calcite and barium carbonate and not the REE carbonates.
Keywords: Light Rare Earth Elements, Heavy Rare Earth Elements, Microflotation, Lignin Sulfonate
  • Poster
    IMPC 2016 - XXVIII International Mineral Processing Congress, 11.-15.09.2016, Quebec, Canada

Permalink: https://www.hzdr.de/publications/Publ-24707
Publ.-Id: 24707


Surface Energy Heterogeneities - New Insights to the Microprocesses of Flotation Separation of Minerals

Rudolph, M.ORC; Hartmann, R.
Especially the modern fine grained and polymetallic deposits call for a continuation in process development and even more so in better understanding the flotation process which is based on the selective hydrophobization/hydrophilization of minerals. This poster will present novel insights on the hydrophobization of various mineral particles, i.e. silicates, semi-soluble salt type minerals and metal oxides with different collector molecules. We investigate the effect of the collectors on the surface energy distribution which is determined with inverse gas chromatography. With this method it is possible to assess the wettability of particles without the difficulties encountered with the conventional sessile drop and penetration methods. By applying inverse gas chromatography we can show that it is due to the collector adsorption the reduction of the highly energetic moieties which only make up less than 10 percent of the particle surface. Furthermore we can present the effect of collector adsorption on the different surface energy components, i.e. disperse and specific interactions. By calculating the free energy of interaction between a particle and a bubble immersed in water using the complex surface energy information we can find a good correlation to the flotation response, i.e. recovery determined with classic microflotation experiments in the Hallimond tube. The minerals used are: quartz, apatite and magnetite. The collectors assessed are cationic and different anionic surfactants at various pH and collector concentration.
Keywords: Surface Free Energy, Wettability, Heterogeneity, Flotation, Particle Bubble Interactions
  • Poster
    IMPC 2016 - XXVIII International Mineral Processing Congress, 11.-15.09.2016, Quebec, Canada

Permalink: https://www.hzdr.de/publications/Publ-24706
Publ.-Id: 24706


Investigation on the fine particle flotation of a carbonate-rich apatite ore from Vietnam

Hoang, D. H.; Rudolph, M.ORC; Schubert, H.
The phosphate beneficiation process is facing a lot of challenges, especially in case of flotation of an apatite ore which is rich in carbonate and sedimentary finely disseminated phosphate minerals. The effect of mineral fineness combined with the presence of carbonate minerals which have mineralogical similarities with phosphate minerals is the reason for reduced selectivity of separation and low recoveries in froth flotation. The fine intergrowths in complex phosphate ores require very fine grinding for liberation in flotation. However, high fineness strongly effects the bubble-particle collisions and the attachment processes, a negative effect on the rheological properties of the slurry, a decrease of the flotation kinetics, and an increase of the entrainment of fine gangue particles.In order to find out the suitable flotation process for the separation of carbonates from the finely disseminated sedimentary phosphate ores, two process complexes are distinguished: the reagent regime and the hydrodynamics of the three-phase system. Especially the turbulent conditions are key to get high collision and attachment between particles and bubbles. The hydrodynamics of the three-phase system relate directly to many sub-processes of the flotation, such as air dispersion, mixing of the slurry and particle-bubble collision and attachment in the high-turbulent rotor stream. In flotation research and practice the control of the hydrodynamics has been a neglected field for a long time, above all for the flotation of fine and finest particles.
In this study, the effects of some important hydrodynamics parameters such as solid content, impeller speed, and air flow rate on the flotation performance were investigated and evlauated.
The flotation rate constant is measured experimentally and compared to the flotation rate kinetic models. Bubble size and energy distribution rate are measured for calculation based on the flotation kinetic model to understand the influence of these factors on flotation behaviour.
  • Lecture (Conference)
    Tagung 2016 "Aufbereitung und Recycling", 09.-10.11.2016, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24705
Publ.-Id: 24705


Untersuchung von dynamischen Schaumeigenschaften der Flotation – Stabilität, Struktur und Wassergehalt

Rudolph, M.ORC; Klöpfel, K.; Michaux, B.
Die Eigenschaften der Schaumphase in der Schaumflotation sind entscheidend für den Erfolg der Trennung und Anreicherung von Partikeln im Gesamtprozess der Flotation. Einige Autoren betrachten gar die Schaumphase als eigene Trennzone. Neben der Schaumhöhe und der mittleren Verweilzeit von Blasen spielen die Blasengrößenverteilung und der Wassergehalt, beide als Funktion der Höhe, eine wichtige Rolle. In der Masterarbeit von Frau Karin Klöpfel wurden Schaumeigenschaften von flotationsrelevanten Systemen das erste Mal mit dem dynamischen Schaumanalysator DFA 100 der Firma Krüss untersucht. Es wurden drei unterschiedliche Messprinzipien kombiniert, nämlich die zeitabhängige Auswertung der Schaumhöhe (Lokalität der Grenzflächen Trübe-Schaum und Schaum-Luft) sowie die zeit- und höhenabhängigen Bestimmungen von Blasengrößenverteilungen und Wassergehalten. Im Rahmen der Studie wurde die Komplexität des Systems sukzessive erhöht. Zu Beginn werden unterschiedliche Schäumermoleküle ohne Partikel verglichen. Es folgt eine Diskussion von spezifischen Ioneneffekten auf die Schäumerwirkung. Nachfolgend werden den Schäumersystemen entweder hydrophile oder hydrophobe sphärische Glaspartikel zugefügt. Zum Abschluss der Untersuchungen wird eine akademische binäre Mischung von Mineralen unterschiedlicher selektiver Hydrophobierung und Größenklassen betrachtet.
  • Poster
    Tagung 2016 "Aufbereitung und Recycling", 09.-10.11.2016, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24704
Publ.-Id: 24704


Zusammenfassung der Beiträge eines Sonderheftes im International Journal of Mineral Processing zum 90. Geburtstag von Prof. Heinrich Schubert

Rudolph, M.ORC; Peuker, U. A.ORC
Zu Beginn des Jahres feierte Prof. Heinrich Schubert seinen 90. Geburtstag. Ihm zu Ehren wurde in der renommierten Fachzeitschrift International Journal of Mineral Processing ein Sonderheft zusammengestellt mit Beiträgen aus aller Welt und mit Bezug zu Prof. Schuberts Wirken. Ein besonderes Augenmerk liegt auf neuesten Beiträgen im Bereich der turbulenten hydrodynamischen Betrachtung des Flotationsprozesses, einer Entwicklung in der Forschung, die von Prof. Schuberts Beiträgen inspiriert wurden und immer mehr Beachtung finden. Der Vortrag fasst die Beiträge zusammen und gibt somit einen Überblick über das nachhaltige Wirken von innovativen Ideen und Ansätzen der „Freiberger Schule“ um Prof. Schubert.

Sonderheft:
International Journal of Mineral Processing, Heft 156, 2016
ISSN 0301-7516
  • Invited lecture (Conferences)
    Tagung 2016 "Aufbereitung und Recycling", 09.-10.11.2016, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24703
Publ.-Id: 24703


Design and performance of an ionisation chamber for the measurement of low alpha-activities

Hartmann, A.; Hutsch, J.; Krüger, F.; Sobiella, M.; Wilsenach, H.; Zuber, K.
A new ionisation chamber for alpha-spectroscopy has been built from radio-pure materials for the purpose of investigating long lived alpha-decays. The measurement makes use of pulse shape analysis to discriminate between signal and background events. The design and performance of the chamber is described in this paper. A background rate of View the MathML source(10.9±0.6)countsperday in the energy region of 1–9 MeV was achieved with a run period of 30.8 days. The background is dominantly produced by radon daughters.
Keywords: Frisch grid; Ionisation chamber; Alpha-decay

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Permalink: https://www.hzdr.de/publications/Publ-24702
Publ.-Id: 24702


Highly Mismatched GaAs1-xNx and Ge1-xSnx Alloys Prepared by Ion Implantation and Ultrashort Annealing

Zhou, S.ORC
Doping allows us to modify semiconductor materials for desired properties such as conductivity, bandgap, and/or lattice parameter. A small portion replacement of the highly mismatched isoelectronic dopants with the host atoms of a semiconductor can result in drastic variation of its structural, optical, and/or electronic properties. Here, the term 'mismatch' describes the properties of atom size, ionicity, and/or electronegativity. In this talk, we present the fabrication of two kinds of highly mismatched semiconductor alloys, i.e., Ge1-xSnx [1] and GaAs1-xNx [2]. The results suggest an efficient above-solubility doping induced by non-equilibrium methods of ion implantation and ultrashort annealing. Pulsed laser melting promotes the regrowth of monocrystalline Ge1-xSnx, whereas flash lamp annealing brings about the formation of high quality GaAs1-xNx with room temperature photoluminescence. The bandgap modification of Ge1-xSnx and GaAs1-xNx has been verified by optical measurements of spectroscopic ellipsometry and photoluminescence, respectively. In addition, effective defect engineering in GaAs has been achieved by flash lamp annealing, by which a quasi-temperature-stable photoluminescence at 1.3 um has been obtained [3, 4]. [1] K. Gao, et al., APL 105, 042107 (2014); [2] K. Gao, et al., APL 105, 012107 (2014); [3] K. Gao, et al., JAP 114, 093511 (2013); [4] S. Prucnal, et al., Opt. Express, 20, 26075 (2012).
  • Lecture (Conference)
    DPG-Frühjahrstagung 2016, 06.-11.03.2016, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-24701
Publ.-Id: 24701


Following our DREAMS (DREsden Accelerator Mass Spectrometry)

Merchel, S.; DREAMS-Team; DREAMS-Users; DREAMS-Friends
Since 2011 the DREAMS (DREsden Accelerator Mass Spectrometry) facility [1] produces data of several long-lived radionuclides (Tab. 1).

Table 1: Radionuclides measured at DREAMS. Updated from [1]. 44Ti and actinides are under development.
Nuclide(s) t1/2 [Ma] AMS material Blank level [10-16] Sample ratios [10-12]
10Be (/9Be) 1.387 BeO 5 0.01-300
26Al (/27Al) 0.705 Al2O3 6 0.001-60
36Cl (/35Cl) 0.301 AgCl 4 0.007-700
41Ca (/40Ca) 0.104 CaF2 20 0.006-9000
129I (/127I) 15.7 AgI 200 0.5-200

AMS reduces background and interfering signals resulting from molecular ions and isobars enormously. Thus, AMS provides much lower detection limits compared to conventional MS or decay counting. DREAMS offers excellent measurement capabilities also for external users (see www.hzdr.de/ibc for beam time application).
Long-lived radionuclides have thousands of exciting applications, especially within environmental and geosciences. In nature, the so-called cosmogenic nuclides (CNs) are products of nuclear reactions induced by primary and secondary cosmic rays. Hence, they can be found in extraterrestrial material such as meteorites - originating from the asteroid belt, the Moon or Mars - and lunar samples in higher concentrations (e.g. ~1010 10Be atoms/g or < 0.5 mBq/g). A combination of several CNs is used to reconstruct the exposure history of this unique material while in space (irradiation age) and on Earth (terrestrial age).
Though, in terrestrial material the concentrations are typically only on the order of 104-109 atoms/g (i.e. μBq/g - nBq/g) for 10Be produced in the Earth’s atmosphere, then transported to the surface and further absorbed and incorporated at and in e.g. sediments or ice. Some of the lowest 10Be concentrations (~103 atoms/g), produced in-situ by neutron- and muon-induced nuclear reactions from e.g. oxygen and silicon in quartz, can be found in samples taken from the Earth’s surface. The concentrations of atmospheric or in-situ produced CNs record information that is used to reconstruct sudden geomorphological events such as volcanic eruptions, rock avalanches, tsunamis, meteor impacts, earthquakes [e.g. 2] and glacier movements. These movements and data from ice cores give also hints for the reconstruction of historic climate changes and provide information for the validation of climate model predicting future changes. Slower processes such as sedimentation, river incision and erosion rates can also be investigated and indirect dating of bones as old as several Ma’s is possible. Finally, remnants of supernova-produced nuclides can also be found in deep-sea archives (sediment, crust, nodule) [e.g. 3].
Anthropogenic production e.g. by release from nuclear reprocessing, accidents and weapon tests led to increased radionuclide levels in surface water, ice and soil (36Cl, 129I,…). Hence, some nuclides can be used as tracers to follow pathways in oceanography, to date and identify sources of groundwater, to perform retrospective dosimetry and to study aspects in radioecology and pharmacology. Obviously, also nuclear installation materials are radioactive (41Ca,…).

Radiochemistry

Typical measurement times are on the order of one hour per sample. However, radiochemical separation of the nuclides of interest is absolutely essential and may take from several days for simple matrices (ice, water) to several weeks for more complicated ones (rock, sediments,…).
DREAMS offers external users to perform this sample preparation of AMS targets in two dedicated chemistry labs at Dresden since 2009. Up to several hundreds of samples from interdisciplinary research topics such as astronomy, climate, cosmochemistry and geology could be transformed into AMS material (Tab. 1) showing reasonable to excellent performance. Besides our constant approach to become a little better every day, sometimes very new challenges can arise due to the low availability of the sample material, low radionuclide concentration or a possible contamination of the sample with disturbing elements and nuclides.

Two examples of challenges

Ice samples are always in our focus. As we were facing problems with 10Be contamination in "dirty" ground ice, instead, we measured 36Cl and natCl by isotope dilution in permafrost ice wedge samples as heavy as 1.6 kg. The chemical yield of AgCl was only 20-35% (and is a function of total natCl), which might be improved by preceding preconcentration steps.
The determination of in-situ or atmospherically produced 26Al in marine and terrestrial sediments suffered sometimes from very low chemical yields. This seems to be mainly caused by redissolving Al(OH)3 in the very last washings. We hope to overcome the problem by longer waiting times, i.e. increased altering of the hydroxides making them less-soluble.

Acknowledgments: Thanks to J. Feige, A. Gärtner, S. Gurlit, P. Ludwig, D. Rodrigues, T. Opel, T. Smith and several students for providing/processing samples and/or ICP-MS.

[1] G. Rugel et al., Nucl. Instr. Meth. Phys. Res. B. 2016, 370, 94-100.
[2] W. Schwanghart et al., Science 2016, 351, 147-150.
[3] A. Wallner et al., Nature 2016, 532, 69-72.
Keywords: accelerator mass spectrometry, radionuclide, radiochemistry
  • Poster
    26. Seminar Aktivierungsanalyse und Gammaspektroskopie (SAAGAS 26), 20.-22.02.2017, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-24700
Publ.-Id: 24700


Application of Ion Beams to Fabricate and Tune Properties of Dilute Ferromagnetic Semiconductors

Zhou, S.ORC
Combining semiconducting and ferromagnetic properties, dilute ferromagnetic semiconductors (DFS) have been under intensive investigation for more than two decades. Mn doped III-V compound semiconductors have been regarded as the prototype of the type. In this contribution, we will show how the implantation technique, a standard method for doping Si in microelectronic industry, can be utilized in fabricating and deeper understanding of DFS. First, ion implantation followed by pulsed laser melting (II-PLM) provides an alternative to the widely used low-temperature molecular beam epitaxy (LTMBE) approach in the preparation of diverse DFS. The prepared DFS materials exhibit pronounced magnetic anisotropy, large X-ray magnetic circular dichroism as well as anomalous Hall effect and magnetoresistance [1-9]. Going beyond LT-MBE, II-PLM is successful to bring two new members, GaMnP and InMnP, into the family of III-Mn-V. Both GaMnP and InMnP films show clear signatures of ferromagnetic coupling and an insulating behavior. Second, helium ions can be used to precisely compensate the holes while keeping the Mn concentration constant [10-12]. We monitor the change of Curie temperature (TC) and conductivity. For a broad range of samples including (Ga,Mn)As and (Ga,Mn)(As,P) with various Mn and P concentrations, we observe a smooth decrease of TC over a wide temperature range with carrier compensation while the conduction is changed from metallic to insulating. In the low compensation regime, we can tune the uniaxial magnetic easy axis of (Ga,Mn)(As,P) from out-of-plane to in-plane with an isotropic-like intermediate state. These materials synthesized or tailored by ion beams provide an alternative avenue to understand how carrier-mediated ferromagnetism is influenced by localization.

[1] M. Scarpula, et al., Phys. Rev. Lett. 95, 207204 (2005).
[2] D. Bürger, S. Zhou, et al., Phys. Rev. B 81, 115202 (2010).
[3] S. Zhou, et al., Appl. Phys. Express 5, 093007 (2012).
[4] M. Khalid, …, S. Zhou, Phys. Rev. B 89, 121301(R) (2014).
[5] Y. Yuan, … S. Zhou, IEEE Trans. Magn. 50, 2401304 (2014).
[6] M. Khalid, …, S. Zhou, J. Appl. Phys. 117, 043906 (2015).
[7] Y. Yuan, …, S. Zhou, J. Phys. D: Appl. Phys. 48, 235002 (2015).
[8] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001 (2015).
[9] Y. Yuan, …, S. Zhou, ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[10] L. Li, S. Yao, S. Zhou, et al., J. Phys. D: Appl. Phys. 44 099501 (2011).
[11] L. Li, …, Shengqiang Zhou, Nucl. Instr. Meth. B 269, 2469-2473 (2011).
[12] S. Zhou, et al., Phys. Rev. B 95, 075205 (2016).
  • Lecture (Conference)
    45th International School & Conference on the Physics of Semiconductors, 19.-24.06.2016, Szczyrk, Poland
  • Invited lecture (Conferences)
    24th Conference on Application of Accelerators in Research and Industry, 30.10.-04.11.2016, Fort Worth, USA
  • Lecture (Conference)
    DPG-Frühjahrstagung 2016, 06.-11.03.2016, Regensburg, Germany
  • Poster
    MML2016 Workshop at DESY, 14.-16.12.2016, Hamburg, Germany
  • Invited lecture (Conferences)
    Invited lecture at Shanghai University, 07.07.2016, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-24699
Publ.-Id: 24699


Precisely doping semiconductors by ion implantation

Zhou, S.ORC
Precisely doping semiconductors by ion implantation, an invited lecture at University of Warsaw
  • Lecture (others)
    Invited seminar at University of Warsaw, 22.09.2016, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-24698
Publ.-Id: 24698


Ion implantation + sub-second annealing: a route towards hyperdoped semiconductors

Zhou, S.ORC
Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. For example, Ga hyperdoped Ge reveals superconductivity and Mn hyperdoped GaAs represents a typical ferromagnetic semiconductor. Ion implantation followed by annealing is a well-established method to dope Si and Ge. This approach has been maturely integrated with the IC industry production line. However, being applied to hyperdoping, the annealing duration has to be shortened to millisecond or even nanosecond. The intrinsic physical parameters related to dopants and semiconductors (e.g. Solubility, diffusivity, melting point and thermal conductivity) have to be considered to choose the right annealing time regime. In this talk, we propose that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. The examples include magnetic semiconductors [1-4], highly mismatched semiconductor alloys (Ge1-xSnx [5] and GaAs1-xNx [6]), n++ Ge [7] and chalcogen doped Si [8, 9].

[1] M. Khalid, et al., Phys. Rev. B, 89, 121301(R) (2014).
[2] S. Zhou, J. Phys. D: Appl. Phys,. 48, 263001 (2015).
[3] S. Prucnal, et al., Phys. Rev. B, 92, 222407 (2015).
[4] Y. Yuan, et al., ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[5] K. Gao, et al., Appl. Phys. Lett., 105, 042107 (2014).
[6] K. Gao, et al., Appl. Phys. Lett.., 105, 012107 (2014) .
[7] S. Prucnal, et al., Sci. Reports, 6, 27643 (2016).
[8] S. Zhou, et al., Sci. Reports, 5, 8329 (2015).
[9] Y. Berencén, et al., ACS Photonics, submitted (2016).
  • Invited lecture (Conferences)
    The 26th annual meeting of MRS-J, 19.-22.12.2016, Yokohama, Japan
  • Invited lecture (Conferences)
    Invited lecture at Shanghai Institute of Microsystem And Information Technology, 05.07.2016, Shanghai, China
  • Invited lecture (Conferences)
    Invited lecture at University of Electronic Science and Technology of China, 18.07.2016, Chengdu, China
  • Lecture (others)
    Invited seminar at Universidad Complutense de Madrid, 21.-23.01.2019, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-24697
Publ.-Id: 24697


Defect induced magnetism in SiC

Zhou, S.ORC; Wang, Y.; Liu, Y.; Hübner, R.; Gemming, S.; Helm, M.
Defect induced magnetism, which can be controllably generated by ion or neutron irradiation, is attracting intensive research interest. It not only challenges the traditional opinions about magnetism, but also has some potential applications in spin-electronics. SiC is a new candidate for the investigation of defect-induced ferromagnetism after graphitic materials and oxides due to its high material purity and crystalline quality [1, 2]. In this contribution, we made a comprehensive investigation on the structural and magnetic properties of ion implanted and neutron irradiated SiC samples. In combination with X-ray absorption spectroscopy, high-resolution transmission electron microscopy and first-principles calculations, we try to understand the mechanism in a microscopic picture.
For neon or xenon ion implanted SiC, we identify a multi-magnetic-phase nature [3]. The magnetization of SiC can be decomposed into paramagnetic, superparamagnetic and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. By combining X-ray magnetic circular dichroism and first-principles calculations, we clarify that p-electrons of the nearest-neighbor carbon atoms around divacancies are mainly responsible for the long-range ferromagnetic coupling [4]. Thus, we provide a correlation between the collective magnetic phenomena and the specific electrons/orbitals.
With the aim to verify if a sample containing defects through its bulk volume can persist ferromagnetic coupling, we applied neutron irradiation to introduce defects into SiC [5]. Besides a weak ferromagnetic contribution, we observe a strong paramagnetism, scaling up with the neutron fluence. The ferromagnetic contribution only occurs in a narrow fluence window or after annealing. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: Defects favor spin polarization at the expense of magnetic interaction. Although both Raman scattering and X-ray diffraction reveal essential structure damage to SiC due to irradiation, high-resolution transmission electron microscopy does not detect significant structural variation even upon the largest neutron fluence.

[1] L. Li, et al., Appl. Phys. Lett. 98, 222508 (2011).
[2] Y. Wang, et al., Phys. Rev. B 90, 214435 (2014).
[3] Y. Wang, et al., Phys. Rev. B 89, 014417 (2014).
[4] Y. Wang, et al., Scientific Reports, 5, 8999 (2015).
[5] Y. Wang, et al., Phys. Rev. B 92, 174409 (2015).
  • Lecture (Conference)
    Atomic structure of nanosystems from first-principles simulations and microscopy experiments, AS-SIMEX 2016, 31.05.-02.06.2016, Helsinki, Stockholm, Finland, Sweden

Permalink: https://www.hzdr.de/publications/Publ-24696
Publ.-Id: 24696


Stabilitätsuntersuchungen an biomimetischen Schichten

Matys, S.; Vogel, M.; Weinert, U.; Suhr, M.; Günther, T.; Pollmann, K.; Raff, J.
Die Quarzmikrowaage als hochsensibler Massendetektor wird derzeit für eine zunehmende Anzahl unterschiedlicher Fragestellungen in verschiedenen wissenschaftlichen Bereichen eingesetzt und auf ihre Tauglichkeit getestet. Die Schichtbildung von Polyelektrolyten mittels Layer-by-Layer-Technik sowie die nachfolgende Abscheidung von S-layer-Proteinen und die Bildung von metallischen Nanopartikeln auf modifizierten Schwingquarzen wurde anhand von Frequenzänderung und Dissipation gemessen und die stattfindenden Wechselwirkungen auf der Quarzoberfläche diskutiert.
Keywords: biomimetische Schichten, Quarzmikrowaage, Frequenzänderung, Dissipation, S-Layer, Polyelektrolyte
  • Lecture (others)
    QCM Workshop, 07.07.2016, Darmstadt, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-24695
Publ.-Id: 24695


Combined hyperspectral and lithogeochemical estimation of alteration intensities in a volcanogenic massive sulfide deposit hydrothermal systems: A Case study from northern Canada

Laakso, K.; Peter, J.; Rivard, B.; Gloaguen, R.
The most intense hydrothermally altered rocks in volcanogenic massive sulfide (VMS) deposit systems occur in the stratigraphically underlying feeder zone. This alteration zone is typically much larger than the mineralization itself, and hence the ability to detect such alteration by optical remote sensing can be invaluable for mineral exploration. Our investigation focuses on assessing the applicability of hyperspectral data to determine trends in hydrothermal alteration intensity in and around the Izok Lake VMS deposit in northern Canada. To this end, we linked hydrothermal alteration intensity information based on two indices, the Ishikawa (AI) and chlorite-carbonate-pyrite (CCPI), to hyperspectral field and laboratory data in three dimensions. Our results suggest that chlorite group minerals display variable chemical composition across the study area that broadly correlates with hydrothermal alteration intensity.
Keywords: Hyperspectral, VMS, hydrothermal, alteration index, mineral exploration
  • Contribution to proceedings
    WHISPERS 2016 - 8th Workshop on Hyperspectral Image and Signal Processing : Evolution in Remote Sensing, 21.-24.08.2016, Los Angeles, USA

Permalink: https://www.hzdr.de/publications/Publ-24694
Publ.-Id: 24694


Distribution of REE minerals in Fluorite Flotation at the Vergenoeg Mine, South Africa

Minz, F. E.; Kern, M.; Birtel, S.; Höfig, T. W.; Krause, J.; Gutzmer, J.
The ore of the Vergenoeg fluorite mine, South Africa, contains rare earth elements in concentrations that may be of commercial interest. To assess the distribution of the rare earth minerals in the industrial flotation process currently used to produce fluorite concentrates, one mining block, that was carefully chemically, mineralogically and petrographically characterised, was fed to the flotation plant and subsequently the plant was systematically sampled. Mineral liberation analysis was conducted on the feed and the flotation products. Monazite and xenotime are the two main rare earth minerals. They are microcrystalline and occur mostly in association with each other and with iron oxide minerals in the ground flotation feed. A Particle Tracking technique was used to process the mineral liberation analysis and to assess the flotation behaviour of monazite and xenotime. Based on the study, different flotation behaviour was proposed for liberated and locked monazite and xenotime. The highest grade of monazite and xenotime was found in the tailing sample from the second cleaner unit of the flotation plant. Monazite and xenotime show high degree of liberation in this product. The tailings, especially of the second cleaner unit, were recommended for further beneficiation of rare earth elements.
  • Lecture (Conference)
    Process Mineralogy’17, 20.-22.03.2017, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-24693
Publ.-Id: 24693


Magnetic Force Microscopy studies of synthetic perpendicular anisotropy antiferromagnets modified by ion beam irradiation

Samad, F.; Böhm, B.; Koch, L.; Ganss, F.; Arekapudi, S. S. P. K.; Lenz, M.; Stienen, S.; Hellwig, O.
By using ion beam irradiation of different energy and flux we modify and tune the magnetic reversal and microstructure in synthetic perpendicular anisotropy antiferromagnets consisting of [(Co/Pt)Co/Ru] multilayer systems. The magnetic energy balance between antiferromagnetic interlayer exchange and dipolar fields in the initial state of the samples has been tuned to have two local energy minima, one for laterally correlated and vertically anti-correlated magnetic structure (single domain antiferromagnet) and the other for laterally anti-correlated and vertically correlated magnetic structure (ferromagnetic stripe domains) [1]. Ion beam irradiation is then subsequently used to locally alter the magnetic microstructure from one state to the other to create laterally co-existing phases and study their reversal behavior in external magnetic fields using Magnetic Force Microscopy.
  • Poster
    Frühjahrestagung der Deutschen Physikalischen Gesellschaft, 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24692
Publ.-Id: 24692


Impact of ion irradiation on magneto-resistance properties of synthetic antiferromagnets based on [(Co/Pt)X-1Co/Ru]N multilayers

Böhm, B.; Samad, F.; Koch, L.; Arekapudi, S. S. P. K.; Ganss, F.; Lenz, M.; Stienen, S.; Hellwig, O.
The tuning of the magnetic properties of antiferromagnetically (AF) coupled multilayer films by ion beam irradiation has been investigated. Stacks of Co/Pd respectively Co/Pt multilayers, AF-coupled by Ru or Ir interlayers, have been useful for studying the energy contribution of interlayer exchange, perpendicular anisotropy and long range dipole interactions. The system shows a complex mixture of magnetic phases that can be tuned by the number of repeats of the multilayers (X). A lateral homogeneous AF remanent structure occurs for small X due to the dominance of the AF-coupling. For large X the demagnetisation energy prevails and ferromagnetic stripe domains evolve. With ion irradiation the balance of the energy contributions can be locally manipulated, thus a lateral heterogeneous structure of magnetic phases may be realised. Initial irradiation studies will be discussed.
  • Poster
    Frühjahrestagung der Deutschen Physikalischen Gesellschaft, 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24691
Publ.-Id: 24691


Manipulation of AF-Coupled Thin Film Systems by Ion Beam Irradiation

Koch, L.; Samad, F.; Böhm, B.; Ganss, F.; Arekapudi, S. S. P. K.; Lenz, M.; Stienen, S.; Hellwig, O.
The tuning of the magnetic properties of antiferromagnetically (AF) coupled multilayer films by ion beam irradiation has been investigated. Stacks of Co/Pd respectively Co/Pt multilayers, AF-coupled by Ru or Ir interlayers, have been useful for studying the energy contribution of interlayer exchange, perpendicular anisotropy and long range dipole interactions. The system shows a complex mixture of magnetic phases that can be tuned by the number of repeats of the multilayers (X). A lateral homogeneous AF remanent structure occurs for small X due to the dominance of the AF-coupling. For large X the demagnetisation energy prevails and ferromagnetic stripe domains evolve. With ion irradiation the balance of the energy contributions can be locally manipulated, thus a lateral heterogeneous structure of magnetic phases may be realised. Initial irradiation studies will be discussed.
  • Poster
    Frühjahrstagung der Deutschen Physikalische Gesellschaft, 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24690
Publ.-Id: 24690


Multiscale Self-Assembly of Quantum Dots into an Anisotropic Three-Dimensional Random Network

Ilday, S.; Ilday, F.; Hübner, R.; Prosa, T.; Martin, I.; Nogay, G.; Kabacelik, I.; Mics, Z.; Turchinovich, D.; Ustunel, H.; Toffoli, D.; Friedrich, D.; Schmidt, B.; Heinig, K.-H.; Turan, R.
One of the well-known challenges in design of nanomaterials is to simultaneously achieve material properties pertaining to few-atom scale and bulk properties through which the material connects to other materials or interacts with devices. This is difficult because properties arising from physics at different scales are often mutually exclusive. An important example is the 30 year-old problem of realizing a connected-but-confined Si nanostructure embedded in a dielectric matrix (e.g., SiO2) that simultaneously brings together quantum-dot (QD)-like optical properties and good electrical conduction. Here, we solve this problem through creation of a hierarchically self-assembled anisotropic random network of Si QDs: At the atomic scale, QDs are formed, which sparsely interconnect without inflating their diameters to form an isotropic random network, and larger scales, this network becomes anisotropic, preferentially growing in the vertical direction to form nanowire-like structures. We report simultaneous achievement of good electrical conductivity (~0.1 S/cm) and a bandgap tuneable over the visible light range (from 1.8 to 2.7 eV).
In order to determine how to self-assemble such a topology without using advanced control over dynamical details of the system, we developed a toy model of the stochastic deposition process, from which we related the intended topology to parameters governing stochastic growth and determined the experimental conditions that can give rise to it. Monte Carlo and Molecular Dynamics simulations are performed to guide our methodology and fabrication was done using magnetron sputter deposition. The two leverages that we used for multiscale self-assembly were as follows: (i) We keep the substrate “cold” and adjust how “hot” the deposited particles are. This way, we create spatio-temporal temperature gradients on the surface and thereby, we control surface diffusion and promote vertical growth in the microscale resembling nanowires. (ii) We fine-tune the thin-film stoichiometry in order to control the phase-separation. This way, we control the nominally unstable medium that QDs are embedded in and limit further inflation of their diameters in the atomic scale. This way we show that self-assembly under nonequilibrium conditions and nonlinear dynamics sweeps aside a large number of factors that influence the details of thin-film growth, but provides a couple of simple “rules” (with clearly identifiable corresponding experimental conditions) to determine the final morphology. The generality and material-independence of this methodology is strongly suggestive of possibility to apply it to solve a variety of other nanomaterial problems, which also pertain to multiple scales.
  • Poster
    2016 MRS Spring Meeting & Exhibit, 28.03.-01.04.2016, Phoenix, AZ, USA

Permalink: https://www.hzdr.de/publications/Publ-24689
Publ.-Id: 24689


Ion Implantation and Annealing Based Synthesizing of AIII-BV Nanostructures in SiO2/Si Matrix

Kopycinski, P.; Prucnal, S.; Pyszniak, K.; Grudzinski, W.; Zuk, J.
Most of modern electronics manufacturing is based on silicon. But because of its indirect energy band gap silicon cannot be used as an efficient light source. Therefore from economical and technological points of view it is important to find light sources than can be integrated into Si technology. One of the possible solutions is to integrate AIII-BV semiconductor nanocrystals inside Si-based matrices. For synthesis of such structures sequential ion implantation and annealing techniques can be used.In this work As+ + In+and As+ + Ga+ions were implanted into SiO2(100nm)/Si. Flash Lamp Annealing (FLA) in the ms range with preheating was employed within a wide range of annealing parameters such as temperature and time. In that way different sizes of InAs and GaAs nanocrystals were obtained.
To investigate optical properties of InAs and GaAs structures we used lowtemperature photoluminescence (PL) and micro-Raman spectroscopic techniques including 2D mapping. PL spectra were obtained in a temperature range from 10K up to RT. Raman spectroscopy was performed at room temperature. The Raman spectra confirms very good quality of InAs and GaAs crystals, and deconvoluted PL spectra give interesting information about expected quantum size effect - related blue shift and nanocrystals sizes.
Keywords: Flash lamp annealing, Si, GaAs, ion implantation
  • Poster
    45th International School & Conference on the Physics of Semiconductors SZCZYRK, POLAND June 18th – 24th, 2016, 18.-24.06.2016, Szczyrk, Poland

Permalink: https://www.hzdr.de/publications/Publ-24688
Publ.-Id: 24688


Band gap engineering in Ge via non-equilibrium thermal processing and Sn doping

Prucnal, S.; Berencen, Y.; Skorupa, W.; Zhou, S.
The incorporation of different functional optoelectronic elements on a single chip enables performance progress which can overcome the downsizing limit in silicon technology. For example, the use of Ge instead of silicon as a basic material in nanoelectronics would enable faster chips containing smaller transistors. As was shown recently, Ge can be used not only for fast electronics but also for optical devices e.g. LEDs and detectors. In order to fully exploit and boost further its unique properties, the alloying of Ge with Sn and ultra-doping with P for n-type conductivity have to be explored. To this day, both Sn and P impurity are introduced into Ge mainly in-situ during the growth process (e.g. using molecular beam epitaxy (MBE) or chemical vapour deposition (CVD)).
In this work, we report on the band gap modification of Ge by Sn alloying and P co-doping.
The doping of Ge was be performed using ion beam implantation of P and Sn with a concentration far exceeding the solid solubility limit of Sn in Ge (>> 0.2%). The implanted Sn was alloyed with Ge using rear-side flash lamp annealing. According to both XRD and HRTEM fabricated layer is single crystalline for the Sn doping up to 6 %. After P-implantation and annealing fabricated GeSn layers are n-type with active carrier concentration above 5×10^19cm-3. The GeSn alloy made by presented method enable the integration of innovative Ge-based devices in the mainstream of Si CMOS technology which can be used for the fabrication of three-dimensional (3D) large-scaleintegration devices with modulated optoelectronic properties.
Keywords: GeSn, flash lamp annealing, n-type doping
  • Poster
    45th International School & Conference on the Physics of Semiconductors, 18.-24.06.2016, Szczyrk, Poland

Permalink: https://www.hzdr.de/publications/Publ-24687
Publ.-Id: 24687


Ultra-doped Ge: old material with new functionalities

Prucnal, S.; Berencen, Y.; Skorupa, W.; Zhou, S.
One of the main obstacles towards wide application of Ge in nanoelectronics is the lack of an efficient doping method for the fabrication of heavily doped Ge layers with well controlled junction depth. In fact, n-type doping of Ge is a key bottleneck in the realization of advanced negative-channel metal-oxide-semiconductor (NMOS) devices. Here we use ion implantation followed by flash-lamp (FLA) annealing for the fabrication of heavily doped Ge with comparably high mobility. In contrast to conventional annealing procedures, rear-side FLA leads to full recrystallization of Ge and dopant activation independently of pre-treatment. The maximum carrier concentration is well above 1020 cm-3 for n-type and above 1021 for p-type doping. The recrystallization mechanism and the dopant distribution during rear-side FLA are discussed in detail.
In this work, we report on the strong mid-IR plasmon absorption from heavily P-doped Ge thin films and superconductivity in Ga implanted Ge obtained by non-equilibrium thermal processing.
Ultra-doped Ge layers were fabricated by ion implantation of P or Ga ions followed by rear-side flash lamp annealing in the millisecond range. This approach, in contrast to conventional annealing procedures, leads to full recrystallization of Ge films and high dopant activation. In this way single crystalline Ge thin films free of defects were obtained. The mid-IR plasmon spectral response at room temperature from those samples was characterized by means of Fourier transform infrared spectroscopy. It is proven that the position of the plasmonic resonance frequency signal can be
tuned as a function of the P concentration.
Keywords: Ge, ion implantation, ultra-doping, n-type
  • Poster
    45th International School & Conference on the Physics of Semiconductors, 18.-24.06.2016, Szczyrk, Poland

Permalink: https://www.hzdr.de/publications/Publ-24686
Publ.-Id: 24686


Mid-infrared plasmonic absorption from heavily doped Ge thin films

Berencén, Y.; Liu, F.; Lang, D.; Voelskow, M.; Skorupa, I.; Kehr, S.; Rebohle, L.; Helm, M.; Skorupa, W.; Zhou, S.; Prucnal, S.
Exploiting plasmonics for mid-IR sensing purposes has become an increasing area of research. The reason is that many molecules present molecular vibrational resonances, which provide spectral fingerprints in the near- and mid-IR region [1, 2]. Of particular interest is the gas detection, diagnostic and medical care. To this day, strong plasmon resonances in the visible and near-IR spectral range have been identified in nanostructured metals such as silver, aluminum and gold [3]. In principle, heavily doped semiconducting materials like Si or Ge could be an interesting alternative to replace metals due to their compatibility with CMOS technology. Indeed, the possibility to control the plasmon resonance frequency in semiconductors via the carrier density opens new route for near- and mid-IR detectors.
In this work, we report on the strong mid-IR plasmon absorption from heavily P-doped Ge thin films obtained by non-equilibrium thermal processing. Ultra-doped Ge layers were fabricated by ion implantation of P ions followed by rear-side flash lamp annealing in the millisecond range. This approach, in contrast to conventional annealing procedures, leads to full recrystallization of Ge films and high P activation irrespective of pre-treatment. In this way, single crystalline Ge thin films free of defects with carrier concentration much above 1×1020 cm-3 and carrier mobility above 260 cm2/(V·s) were obtained. The mid-IR plasmon spectral response at room temperature from those samples was characterized by means of Fourier transform infrared spectroscopy. It is proven that the position of the signal from the plasmon resonance frequency can be tuned as a function of the P concentration.
Keywords: plasmonics, heavily doped n-type Ge, flash-lamp annealing.
[1] A. G. Brolo, Nat. Photonics 6, 709 (2012).
[2] N. Liu, M. Mesch, T. Weiss, M. Hentschel, and H. Giessen, Nano Lett. 10, 2342 (2010).
[3] G. Konstantatos and E. H. Sargent, Nat. Nanotechnology 5, 391 (2010).
Keywords: Ultra-doped Ge, Plasmonics, FLA, Ion implantation
  • Lecture (Conference)
    E-MRS 2016 Spring Meeting (European-Materials Research Society), 02.-06.05.2016, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-24685
Publ.-Id: 24685


Room-temperature extended IR photoresponse from hyperdoped Si p-n photodiodes

Berencén, Y.; Prucnal, S.; Liu, F.; Wang, M.; Zhou, S.; Lang, D.; Skorupa, I.; Helm, M.; Rebohle, L.; Skorupa, W.
The development of room-temperature Si infrared photodetectors, whose range of detection lies on the traditional telecommunication wavelengths around 1300 nm and 1550 nm, is of paramount importance for optical communications, integrated photonics, sensing and medical imaging applications [1]. The typical peak photoresponse of conventional Si photodetectors is between 700 and 900 nm, which is primarily limited by the 1.12 eV-Si band gap. However, such intrinsic material limitation can be overcome by introducing transition metals or chalcogens into the Si band gap at concentrations far above those obtained at equilibrium conditions [1, 2]. This new class of hyperdoped materials with a donor impurity band has been postulated as a viable route to extend the Si photoresponse at the infrared spectral region [3].
In this work, we report on the significant room-temperature photoresponse and performance at the two primary telecommunication wavelengths as exhibited by hyperdoped Si p-n photodiodes fabricated by Se implantation followed by millisecond flash lamp annealing (FLA). The FLA approach in the millisecond range allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase epitaxy induced during pulsed laser annealing [2]. The success of our devices is primarily based on the high quality of the developed n-type hyperdoped material, which is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface.
[1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014).
[2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015).
[3] I. Umezu, J. M. Warrender, S. Charnvanichborikarn, A. Kohno, J. S. Williams, M. Tabbal, D. G. Papazoglou, X. C.Zhang, and M. J. Aziz, J. Appl. Phys. 113, 213501 (2013).
Keywords: Se, Si, hyperdoping, FLA, Ion implantation, Si-based IR photodetectors
  • Lecture (Conference)
    E-MRS 2016 Spring Meeting (European-Materials Research Society), 02.-06.05.2016, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-24684
Publ.-Id: 24684


Structural impact of Cr doping in titanium oxide thin films grown by co-sputtering and flash-lamp annealed

Gago-Fernandez, R.; Prucnal, S.; Pérez-Casero, R.; Caretti, I.; Lungwitz, F.; Cornelius, S.
Titanium dioxide (TiO2) is used in many applications as a photocatalyst. However, TiO2 activity is mostly limited to the UV spectral region due to its wide band-gap (~3eV). For this reason, many efforts1 have been focused on band-gap narrowing to achieve visible-light (VISL) response in TiO2, mostly by doping. Metal (cation) doping increases VISL absorption significantly but, unfortunately, it introduces structural distortions in the host matrix that result in a large number of defects acting as carrier recombination centers.1 Post-processing thermal treatments are normally employed here to improve the structural order.2 In this work, we study the impact of rapid non-contact thermal processes as flash-lamp annealing (FLA) on the electronic structure of Cr-doped TiO2. For this purpose, (amorphous) thin films with different Cr contents were produced at room temperature by magnetron co-sputtering. The dopant concentration was quantified by Rutherford backscattering spectrometry (RBS) whereas the resulting structural phases after FLA were assessed by Raman and X-ray diffraction (XRD). Due to the disordered nature of the samples, the structural characterization has been complemented with local-order information around host and dopant sites from the X-ray near-edge structure (XANES). Finally, the optical properties have been studied by spectroscopic ellipsometry (SE). It is found that FLA can selectively tune the anatase/rutile phase formation in pure TiO2. In addition, films
with low doping (Cr < 6 at.%) display a rutile structure. For higher doping level, the formation of high-valence Cr sites is observed, which seems to be detrimental for the structural promotion. Nonetheless, these sites are thermally unstable and annihilated upon FLA. REFs: 1Asahi et al. SCI 293, 269 (2001); 2W. Zhu et al. PRL 103, 226401 (2009).
Keywords: TiO2, Cr, FLA, XRD, PL
  • Poster
    15th International Conference on Plasma Surface Engineering, 12.-16.09.2016, Garmisch-Partenkirchen, Germany

Permalink: https://www.hzdr.de/publications/Publ-24683
Publ.-Id: 24683


Non-equilibrium thermal processing for hyperdoping Si

Berencén, Y.; Prucnal, S.; Liu, F.; Wang, M.; Zhou, S.; Helm, M.; Rebohle, L.; Skorupa, W.
Hyperdoping has recently emerged as a potential powerful technique to explore new functionalities of semiconductor materials with unique electrical and optical properties [1-3]. Hyperdoping facilitates to introduce dopants into a semiconductor material at concentrations far above those obtained at equilibrium conditions, viz. doping far beyond the solubility limit. Hyperdoped Si with chalcogens or transition metals like Au or Ti has been postulated to be a promising material for many applications, especially for Si-based infrared photodetectors and intermediate band solar cells [2, 3].
In this work, we report on a groundbreaking approach, for hyperdoping Si with Se, consisting of ion implantation followed by millisecond-range flash lamp annealing. This method allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase epitaxy induced during conventional pulsed laser annealing [1]. The resulting Se-hyperdoped Si material is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface. We also present a significant room-temperature sub-band gap photoresponse exhibited by Se-hyperdoped Si p-n photodiodes that have been fabricated by this novel approach.
[1] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015).
[2] M. J. Sher & E. Mazur, App. Phys. Lett. 105, 032103 (2014).
[3] E. Ertekin, M. T. Winkler, D. Recht, A. J. Said, M. J. Aziz, T. Buonassisi, and J. C. Grossman, Phys. Rev. Lett. 108, 026401 (2012).
Keywords: Hyperdoping, Si, , Se, FLA, ion implantation
  • Invited lecture (Conferences)
    ION 2016 - International Conference of ion implantation and other applications of ions and electrons, 13.-16.06.2016, Kazimierz Dolny, Poland

Permalink: https://www.hzdr.de/publications/Publ-24682
Publ.-Id: 24682


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