The electron transport characteristics of n-type germanium (Ge) thin films have been widely studied
in order to elucidate the underlying mechanisms that govern the performance of Ge-based materials
at low temperatures. In this work, ultra-doped n-type Ge layer with phosphorus (P) fluence of
5.4 × 1014 cm−2 has been prepared by ion implantation followed by millisecond-range flash lamp
annealing (ms-FLA). The structural and charge transport properties of the FLA-treated ultra-doped
Ge:P thin film have been systematically investigated. The resulting material exhibits a high
recrystallization quality and a sheet carrier concentration surpassing 5 × 1014 cm−2, which
corresponds to an electrical activation yield beyond 90%. Moreover, the low-temperature
magnetoresistance measurements, analyzed via the Hikami-Larkin-Nagaoka model, reveal a phase
coherence length of around 75 nm, which exhibits a power-law decay with increasing temperature.
This work suggests potential pathways toward novel design paradigms for future magneto-electronic
devices using Ge-based materials.

β-Ga2O3 presents unique optoelectronic characteristics, making it a favorable material platform for constructing
promising high-power electronics and ultraviolet photonic devices. In this work, we demonstrate bismuth (Bi)
doping as a heavy metal element doping strategy to engineer the band structure and defect landscape of β-Ga2O3.
Bi implantation induces lattice expansion and tensile strain, leading to a gradual redshift in the absorption edge
with increasing doping concentration. First-principles calculations reveal that the substitutional Bi on octahedral
Ga site results in the lattice expanding and the band structure modification. Critically, the hybrid coupling of O-
2p and Bi-6s orbitals creates an intermediate band (IB) with shallow acceptor states. This unique band configuration
enables sub-bandgap photon harvesting, leading to enhancement in ultraviolet photoresponse in
β-Ga2O3:Bi. This work shows Bi doping effects in modifying lattice defects and band hybridization of β-Ga2O3,
establishing IB engineering as a paradigm for advancing high-performance β-Ga2O3-based ultraviolet optoelectronics
and towards p-type doping in wide-bandgap semiconductors.

Face-centered cubic (fcc) Ni-based alloys are among the leading candidates for
structural materials in nuclear reactors, owing to their superior resistance to
extreme environmental conditions and remarkable radiation tolerance. Thus, the
study and modeling of the radiation behavior of such material seem particularly
important to predict its final microstructural evolution. Rutherford backscattering
spectrometry in channeling mode (RBS/C) is extensively utilized for assessing the
structural properties of ion-implanted single crystals, mainly due to the quantitative
nature and depth resolution of the technique. Moreover, different types of
radiation-induced defects have distinct effects on the RBS/C spectra. This study
investigates defect formation in high-temperature ( 800 K) ion-implanted
equiatomic Ni-based single crystals, specifically NiFe and NiFeCoCr, through an
integrative approach that combines structural and mechanical analysis with
advanced simulation methods. To replicate neutron radiation damage, ion
implantations are conducted using 380 keV Ar ions with fluences ranging from
1   1014 up to 1   1016 cm 2. The novelty of this manuscript lies in the use of
molecular dynamics (MD) for modeling and parameterizing structural bending of
the atomic rows near dislocation edges and utilizing the results for Monte Carlo
(MC) simulations using the latest version of the MC-based McChasy-1 code.

Radiative environments can induce defects in the exposed materials, whose
accumulation leads to defect structure transformations and optical quenching.
Therefore, their role is crucial for the fabrication of devices. β-Ga2O3:RE system
seems attractive for prospective optoelectronic applications. In this research,
structural defects created in the crystal lattice upon Sm ion implantation
in (010)-oriented β-Ga2O3 and the recovery after annealing are investigated.
Channeling Rutherford backscattering spectrometry (RBS/c) supported by
McChasy simulations and room-temperature photoluminescence (RT-PL)
spectroscopy are applied to study the structural and optical changes, respectively.
The studies reveal the existence of two different randomly displaced
atoms (RDA)-types of defects in the implanted zone and the optical inactivity
of Sm-dopant ions. Rapid thermal annealing (RTA) in argon at 800 °C for
0.5 min results in the removal of deeply located defects, while the defects
closer to the surface are not influenced significantly. RT-PL measurements
demonstrate the strong luminescence in the visible and ultraviolet regions of
the spectrum.

Muonic atom spectroscopy is a method that can determine absolute nuclear charge radii with typical
relative precision of 10−3. Recent developments have enabled to extend muonic atom spectroscopy
to microscopic target quantities as low as 5 μg. This substantial reduction from the traditional
limit of the order of 100mg is based on a transfer mechanism in a high-pressure hydrogen gas cell,
which transports the muon to the surface of the target material rather than stopping it over a broad
depth range. This approach enables the measurement of absolute nuclear charge radii of long-lived
radioactive isotopes (half-life above ∼ 20 years), but the production of appropriate targets for the
technique has presented some major challenges, such as the formation of organic layers on the
substrate. This study presents a systematic investigation of the stopping efficiency for different target
preparation methods: ion implantation, drop-on-demand printing, and molecular plating. Notable
differences between the three methods were discovered in terms of their performance allowing
to further fine tune the method of choice for future target preparations. Our findings show that
implantation provides appropriate targets for our method with negligible losses. This achievement
opens the landscape of potential measurements to isotopes where high mass separation is required
not achievable with other methods. Furthermore, molecular plated targets performed substantially
better than those prepared using drop-on-demand printing.

Understanding irradiation-induced strain in silicon carbide (SiC) is essential for designing radiation-tolerant ceramic materials. However, conventional methods often fail to resolve nanoscale strain gradients, especially in polycrystalline forms. In this study, we employ nano-beam precession electron diffraction (N-PED) to perform high-resolution, multi-directional strain mapping in both single-crystal 4H-SiC and polycrystalline α-SiC subjected to helium and hydrogen ion irradiation. The high-resolution X-ray diffraction (HR-XRD) simulations of He + H irradiated single-crystal 4H-SiC closely match the strain profiles obtained from N-PED, demonstrating the reliability and accuracy of the N-PED method. In He-irradiated polycrystalline α-SiC at high temperatures, a bubble-depleted zone (BDZ) near the grain boundary (GB) reveals that GBs act as active sinks for irradiation-induced defects. N-PED further shows strain amplification localized at the GBs, reaching up to ∼2.5 %, along with strain relief within the BDZ. To explain this behavior, density functional theory (DFT) calculations of binding and migration energies indicate a strong tendency for Si, C, and He atoms to segregate toward the GB core. This segregation reduces the availability of vacancies to accommodate He atoms and leads to local strain relaxation near the GB. Furthermore, first-principles tensile simulations reveal that Si and C interstitials mitigate He-induced GB embrittlement. Charge density and DOS analyses link this effect to the bonding characteristics between point defects and neighboring atoms at GB. These insights underscore the importance of grain boundary engineering in enhancing radiation tolerance of SiC for nuclear and space applications.

Fe3GaTe2 (FGaT), a two-dimensional (2D) layered ferromagnetic metal, exhibits a high Curie temperature (TC) ∼ 360 K along with strong perpendicular magnetic anisotropy (PMA), making it a promising candidate for energy-efficient, next-generation magnetic devices. However, the vast majority of studies on FGaT to date have been limited to millimeter-sized bulk crystals and exfoliated flakes, which are unsuitable for practical applications and integration into device processing. Also, its combination with other 2D materials to form van der Waals heterostructures has only been achieved by flake stacking. Consequently, the controlled large-scale growth of FGaT and related heterostructures remains largely unexplored. In this work, we demonstrate a breakthrough in the high-quality, large-area growth of epitaxial FGaT thin films on single-crystalline graphene/SiC templates using molecular beam epitaxy. Structural characterization confirms the high crystalline quality of the continuous FGaT/graphene van der Waals heterostructures. Temperature-dependent magnetization and anomalous Hall measurements reveal robust PMA with an enhanced TC well above room temperature, reaching up to 400 K. Furthermore, X-ray absorption and X-ray magnetic circular dichroism spectra provide insight into the spin and orbital magnetic moment contributions, further validating the high TC and robust PMA. These findings are highly significant for the future development of high-performance spintronic devices based on 2D heterostructures, with potential applications in next-generation data storage, logic processing, and quantum technologies.

Historically, molybdenum disulfide (MoS₂) has been employed as an efficient dry lubricant in space due to its low coefficient of friction in vacuum. In contrast, the performance of MoS2 breaks down in the presence of oxygen and water, due to oxidation to MoO₃ and disruption of the van der Waals sliding mechanism. Still, no clear evidence of the structural evolution of the material during friction experiments in different atmospheres has been reported.
MoS₂ coatings of 2 μm thickness were deposited by the filtered Laser-Arc on 100Cr6 substrates with a Cr adhesion layer and exposed to friction tests in vacuum, dry and humid air in a ball-on-disc configuration. Microbeam Rutherford backscattering spectrometry (μ-RBS), was used together with other techniques to investigate the element distribution and structural changes in the wear tracks as well as the wear scars of the 100Cr6 counterbodies. After the friction experiment in dry air, μ-RBS demonstrates the absence of oxygen in the MoS₂ coating, suggesting it does not oxidize. However, in the wear scar of the counterbody, molybdenum, sulfur, and other elements are distributed heterogeneously in different areas, indicating a complex tribochemistry. The results show that μ-RBS can give a valuable contribution to the study of changes in the composition of dry lubricants like MoS₂ in friction experiments.

The interaction of energetic ions with materials is a fundamental process that occurs in fusion reactors, impacting radiation damage, heat deposition, and overall material performance. While previous work has significantly advanced our understanding of electronic stopping in metals, the impact of alloying and irradiation-induced defects remains underexplored, despite their importance for materials in extreme environments. In this work, we combine ab initio simulations with measurements to study electronic stopping in both pristine and defect-containing Fe and EUROFER97. By systematically assessing the influence of alloying and defects, we examine the extent to which structural modifications alter energy dissipation. Our findings contribute to a more rigorous understanding of electronic stopping in fusion-relevant materials and the reliability of simplified approaches in radiation damage simulations

PVA/CNT nanocomposite films with 10, 20, and 30 wt% CNT were prepared by casting evaporation. X-ray diffraction (XRD) confirmed the formation of monoclinic crystal structure with ≈4 nm. The unit cell volume as well as interchain distances decreased from 67.31 to 64.55 ų and from 5.81 × 10^-10 to 5.64 × 10^-10 m, respectively, with the increase in CNT concentrations. Due to sensitivity of PVA/CNT films to trace elements, ion beam techniques RBS, PIXE, and ERDA provide information about the light elements’
content and distribution. SEM showed textured, complex surfaces, with layered structure morphology for PVA/CNT films. TGA exhibits three stages for thermal degradation with a remarkable stage at 230 °C–280°C with major weight losses (67%, 55%, and 60%) for the 10, 20, and 30%CNT films. Fourier Transform Infrared spectroscopy (FTIR) obtained the information on spectroscopic functional groups of the films. (PVA)₉₀ (CNT)₁₀ sample shows a higher brittleness value (2.12 × 10^-3 (MPa)^-3) due to the tensile modulus and the tensile elongation values. Most significantly, optical properties exhibited tunable indirect band gaps: 4.7 eV (10 wt%), 3.75 eV (20 wt%), and 2.9 eV (30 wt%), demonstrating excellent potential for optoelectronic device applications.

Doping of β-Ga2O3 (100) with Si by ion implantation onto heated substrates is investigated. The study reveals complex ion beam-induced defect processes in β-Ga2O3, characterized by the formation of various defect types and their temperature-dependent transformation. By employing X-Ray Diffraction, Rutherford Backscattering Spectrometry, Particle-Induced X-Ray Emission, X-ray Absorption Near Edge Structure Spectroscopy, Transmission Electron Microscopy, and Density Functional Theory analyses, we examine lattice deformation, identify the local environment of dopants, assess electronic structure modifications, and verify the presence of extended defects induced by ion implantation. Our findings highlight the predominant contribution of substitutional and interstitial Si ions incorporated into complexes that act as donors manifesting n-type conductivity, while some fraction of the defects form complexes that act as traps for charge carriers. Notably, no monoclinic phase transformations were observed during implantation despite substrate temperature variations from 300 to 800°C.

The heaviest elements in the periodic table have a low production yield. In order to increase the production yield of the superheavy elements, thicker targets are required than the present molecular plating technique can offer. Therefore, lanthanide thin films, as lighter homologues to the actinides, were prepared by a new electrodeposition method. The trifluoromethanesulfonates (triflates) of the lanthanide salts were dissolved in Dimethylformamide (DMF) and then electrochemically deposited onto substrates of different geometries. These thin films were irradiated with different swift heavy ion beams with energies of over 200 MeV. Thin films were analyzed spectroscopically by Raman and IR measurements before and after irradiation, to investigate chemical changes induced by irradiation.

Silicon carbide has been considered a material for use in the construction of advanced hightemperature
nuclear reactors. However, one of the most important design issues for future reactors is
the development of structural defects in SiC under a strong irradiation field at high temperatures. To
understand how high temperatures affect radiation damage, SiC single crystals were irradiated at
room temperature and after being heated to 800 °C with carbon and silicon ions of energies ranging
between 0.5 and 21 MeV. The number of displaced atoms and the disorder parameters have been
estimated by using the channeling Rutherford backscattering spectrometry. The experimentally
determined depth profiles of induced defects at room temperature agree very well with theoretical
calculations assuming its proportionality to the electronic and nuclear-stopping power values. On
the other hand, a significant reduction in the number of crystal defects was observed for irradiations
performed at high temperatures or for samples annealed after irradiation. Additionally, indications
of saturation of the crystal defect concentration were observed for higher fluences and the irradiation
of previously defected samples.

Black titania nanotubes possess an extraordinary surface functionality while having a high absorbance in the visible light range. In this study, a low-temperature manufacturing approach for dark titania nanotubes is presented: low-energy low-fluence carbon ion implantation. It allows a local chemical reduction, preserves the amorphous structure and induces oxygen vacancies, leading to high electrical conductivity. The material's modification is unveiled on microscopic and macroscopic scales: electrical characteristics are recorded on the nanometer scale using tunneling atomic force microscopy and overall with two-point measurements. The depth-resolved atomic composition is assessed via elastic recoil detection analysis, while optical and X-ray photoelectron spectroscopy elucidate the global chemical binding situation and band gap shifts. This extensive analysis supports the concept of percolated carbon paths that vertically span the nanotubes and provide a substantial contribution to the enhanced conductivity. In combination with the utilization of implantation masks, a versatile route for a targeted and localized material's manipulation towards patterned dark amorphous titania nanotubes is demonstrated that gives rise to innovative materials and smart devices.

The interaction of highly charged ions with surfaces leads to various inelastic processes in which energy is transferred to the surface in an area of few nm2 and within the time scale of femtoseconds [1]. Numerous experiments were conducted over the past years to investigate the interaction of highly charged ions (HCI) with 2D materials where the interaction is reduced to a monolayer and thus the pre-equilibrium regime is investigated [2]. In the case of surfaces and 2D materials, one challenge is to ensure that the surface is free of contaminations [2]. The interaction of gas targets on the other hand are dominated by charge exchange processes with the atoms and molecules of the gas. Our primary goal is to study the interaction of HCI with gas targets in a systematic manner and to compare them to recent results on graphene and other 2D materials. Therefore, a huge parameter space of various ion charge states, ion energies, gas target species and gas pressure needs to be explored.

The experiments conducted at the IBC’s new HCI–transmission setup with Xe projectiles and different target gases, demonstrated the capability of the setup to investigate the interaction of highly charged ions of varying charge states (Xe5+ to Xe37+) with gas targets. The major advantage of this setup is the possibility to make use of different gas targets and the ability to vary pressure, ion energy and charge state in an easy manner, providing the opportunity to conduct extensive systematic studies of the dependency on the interaction of these parameters. The initial set of experiments were conducted at varying pressures ranging from 1E-9mbar up to 5E-4mbar. Fig. 1. shows the related charge state spectra of the incoming Xe25+ ions after passing the gas cell.

[1] Schenkel, T., Hamza, A. V., Barnes, A. V., & Schneider, D. H, Progress in Surface Science, 61(2-4), 23-84 (1999); Aumayr, F., Facsko, S., El-Said, A. S., Trautmann, C., & Schleberger, M., Journal of Physics: Condensed Matter, 23(39), 393001 (2011).
[2] R. Wilhelm, E. Gruber, J. Schwestka, R. Heller, S. Facsko, and F. Aumayr, Applied Sciences 8, 1050 (2018).

Multinary nitrides and oxynitrides offer a range of tunable structural and optoelectronic properties. However, much of this vast compositional space remains to be explored due to the challenges associated with their synthesis. Here, reactive sputter deposition is used to synthesize isostructural polycrystalline zirconium tantalum oxynitride thin films with varying cation ratios and systematically explore their structural and optical properties. All films possess the cubic bixbyite-type structure and n-type semiconducting character, as well as composition-tunable optical bandgaps in the visible range. Furthermore, these compounds exhibit remarkably high refractive indices that exceed a value 2.8 in the non-absorbing sub-bandgap region and reach 3.2 at 589 nm for Ta-rich compositions. Photoemission spectroscopy reveals non-uniform shifts in electron binding energies that indicate a complex interplay of structural and compositional effects on interatomic bonding. In addition to being high-index materials, the measured band edge positions of the films align favorably with the water oxidation and reduction potentials. Thus, this tunable materials family offers prospects for diverse optoelectronics application, including for production of photonic metamaterials and for solar water splitting.

Metal phosphates are gaining recognition as versatile functional materials with a wide range of applications. Depositing these materials as thin conformal layers with atomic layer deposition (ALD) requires a phosphorous precursor. Here, the use of tris(dimethylamino)phosphine (TDMAP) is explored by reporting the characterization of an aluminum phosphate process using TDMAP, the well-known aluminum precursor, trimethylaluminum (TMA), and O₂- plasma as precursors. Films grown with a four-step process (TDMAP - O₂-plasma - TMA - O₂-plasma) at 300 °C have a stoichiometry of Al₁P_0.51O_2.9 and are amorphous, but do contain PO₄ units. Comparing the four-step process with three-step processes omitting one of the two O₂-plasma steps, provides insights in the role of the co-precursors. TMA is able to react with a TDMAP terminated surface but not vice versa. TDMAP has a very low inherent reactivity and requires the use of a co-precursor to remove the ligands of the adsorbed TMA molecules and render the surface reactive for TDMAP adsorption. By implementing a supercycle approach using the (TDMAP - O₂-plasma) sequence and the (TMA - O₂-plasma) sequence as subcycles, more phosphorous rich films can be obtained. The phosphorous content of the deposited aluminum phosphate is shown to have a significant effect on its performance as a battery coating material. While amorphous aluminum metal phosphate is not the prime candidate for this type of coating, our results indicate the importance of phosphorous content as a parameter worth studying.

Growing environmental concerns have driven the switch from lead-containing dielectric perovskite ceramics to lead-free alternatives such as silver niobate tantalate (Ag(Nb1-xTax)O3), where tantalum (Ta) substitution for niobium (Nb) enhances energy storage density. Thin film deposition presents a promising way for fabricating these materials for the use in capacitors. In this study, Ag(Nb1-xTax)O3 (0 ≤ x ≤ 0.5) thin films are synthesised via combinatorial reactive d.c. magnetron sputtering from metallic targets. The chemical and phase composition of the films are comprehensively analysed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, elastic recoil detection analysis, Rutherford backscattering spectrometry, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The findings demonstrate that reactive d.c. magnetron sputtering is a feasible technique for producing complex perovskite oxide thin films with customised chemical composition and microstructure. By enhancing the understanding of the Ag(Nb1-xTax)O3 material system, this study aims to contribute to the development of environmentally benign high-performance dielectrics that could replace lead-based ceramics in energy-storage applications.

The heaviest known elements are produced via fusion reaction by bombarding actinide targets with intense heavy ion beams. The synthesis of actinide targets relies mainly on the molecular plating (MP) technique. Long-term stability of MP produced targets is typically achieved by a conditioning procedure, in which the fresh target is exposed to successively increasing beam intensities. This leads to nontrivial physical and chemical transformations, which are presently poorly understood. To shed light on processes in the initial irradiation stage, we irradiated thin thulium MP films with Cl and Au ions of different fluences, with the latter ranging from 10¹⁰ ions/cm² to 10¹⁴ ions/cm² , and analysed their morphology and composition by a variety of microscopic, spectroscopic and ion beam techniques. The study was conducted on lanthanide targets, which serve as nonradioactive analogues for actinide targets. Combining the results of several methods, we conclude that the MP thin films consist of a mixture of carbonates and formates. Under irradiation, these films transform into amorphous oxides, with a loss of carbon-containing species.

Zinc nitride (Zn₃N₂) comprises earth-abundant elements, possesses a small direct bandgap, and is characterized by a high electron mobility. While these characteristics make this material a promising compound semiconductor for various optoelectronic applications, including for photovoltaics and thin-film transistors, it commonly exhibits unintentional degenerate n-type conductivity. This degenerate character has significantly impeded the development of Zn₃N₂ for technological applications and is commonly assumed to arise from incorporation of oxygen impurities. However, consistent understanding and control of the role of native and impurity defects on the optoelectronic properties of this otherwise promising semiconductor have not yet emerged. Here, we systematically synthesize epitaxial Zn₃N₂ thin films with controlled oxygen impurity concentrations of up to 20 at.% by plasma-assisted molecular beam epitaxy (PA-MBE). Contrary to expectations, we find that oxygen does not lead to degenerate conductivity but instead serves as a compensating defect, the control of which can be used to achieve non-degenerate semiconducting thin films with free electron concentrations in the range of 10¹⁷ /cm³, while retaining high mobilities in excess of 200 cm²/Vs. We find that the electrical properties change from metallic to semiconducting behavior as the oxygen content increases, suggesting the formation of defect complexes in the material. This understanding of the beneficial role of oxygen thus provides a route to controllably synthesize non-degenerate O:Zn₃N₂ for optoelectronic applications.

Ternary nitrides are rapidly emerging as promising compounds for optoelectronic and energy conversion applications, yet comparatively little of this vast composition space has been explored. Furthermore, the crystal structures of these compounds can exhibit a significant amount of disorder, the consequences of which are not yet well understood. Here, the deposition of bixbyite-type ZrTaN3 thin films is demonstrated by reactive magnetron co-sputtering and observed semiconducting character, with a strong optical absorption onset at 1.8 eV and significant photoactivity, with prospective application as functional photoanodes. It is found that Wyckoff-site occupancy of cations is a critical factor in determining these beneficial optoelectronic properties. First-principles calculations show that cation disorder leads to minor deviations in the total energy but modulates the bandgap by 0.5 eV, changing orbital hybridization of valence and conduction band states. In addition to demonstrating that ZrTaN3 is a promising visible light-absorbing semiconductor and active photoanode material, the findings provide important insights regarding the role of cation ordering on the electronic structure of ternary semiconductors. In particular, it is shown that not only cation order, but also the cationic Wyckoff site occupancy has a substantial impact on key optoelectronic properties, which can guide future design and synthesis of advanced semiconductors.

Semiconducting ternary nitrides are a promising class of materials that have received increasing attention in recent years, but often show high free electron concentrations due to the low defect formation energies of nitrogen vacancies and substitutional oxygen, leading to degenerate n-type doping. To achieve non-degenerate behavior, we now investigate a family of amorphous calcium–zinc nitride (Ca–Zn–N) thin films. By adjusting the metal cation ratios in the films, we demonstrate band gap tunability between 1.4 and 2.0 eV and control over the charge carrier concentration across six orders of magnitude, all while maintaining high mobilities between 5 and 70 cm²/(Vs). The combination of favorable electronic properties, low synthesis temperatures, and earth-abundant elements makes amorphous calcium zinc nitride highly promising for future sustainable electronics. Moreover, the successful synthesis of such materials, as well as their broad optical and electrical tunability, paves the way for a new class of tailored functional materials: amorphous nitride semiconductors – ANSs.

The photoelectrochemical performance of Ta₃N₅ photoanodes is strongly impacted by the presence of shallow and deep defects within the bandgap. However, the role of such states in defining the stability under operational conditions is not well understood. Here, we use a highly controllable synthesis approach to create homogenous Ta₃N₅ thin films with tailored defect concentrations to establish the relationship between atomic-scale point defects and macroscale stability. Reduced oxygen contents increase long-range structural order but lead to high concentrations of deep-level states, while higher oxygen contents result in reduced structural order but beneficially passivate deep-level defects. Despite the different defect properties, the synthesized photoelectrodes degrade similarly under water oxidation conditions due to formation of a surface oxide layer that blocks interfacial hole injection and accelerates charge recombination. In contrast, under ferrocyanide oxidation conditions, we find that Ta₃N₅ films with high oxygen concentrations exhibit long-term stability, whereas those possessing lower oxygen contents and higher deep-level defect concentrations rapidly degrade. These results indicate that deep-level defects result in rapid trapping of photocarriers and surface oxidation but that shallow oxygen donors can be introduced into Ta₃N₅ to enable kinetic stabilization of the interface.

Transition metal oxynitrides are a promising class of functional materials for photoelectrochemical (PEC) applications. Although these compounds are most commonly synthesized via ammonolysis of oxide precursors, such synthetic routes often lead to poorly controlled oxygen-to-nitrogen anion ratios, and the harsh nitridation conditions are incompatible with many substrates, including transparent conductive oxides. Here, we report direct reactive sputter deposition of a family of zirconium oxynitride thin films and the comprehensive characterization of their tunable structural, optical, and functional PEC properties. Systematic increases of the oxygen content in the reactive sputter gas mixture enable access to different crystalline structures within the zirconium oxynitride family. Increasing oxygen contents lead to a transition from metallic to semiconducting to insulating phases. In particular, crystalline Zr2ON2-like films have band gaps in the UV−visible range and are n-type semiconductors. These properties, together with a valence band maximum position located favorably relative to the water oxidation potential, make them viable photoanode candidates. Using chopped linear sweep voltammetry, we indeed confirm that our Zr2ON2 films are PEC-active for the oxygen evolution reaction in alkaline electrolytes. We further show that high-vacuum annealing boosts their PEC performance characteristics. Although the observed photocurrents are low compared to state-of-the-art photoanodes, these dense and planar thin films can offer a valuable platform for studying oxynitride photoelectrodes, as well as for future nanostructuring, band gap engineering, and defect engineering efforts.

Atomic layer-deposited (ALD) TiO2 thin films on silicon were deposited using titanium tetrachloride (TiCl4), titanium tetraisopropoxide (TTIP), and tetrakis(dimethylamino)titanium (TDMAT) together with water vapor as the oxidant at temperatures ranging between 75 and 250 °C. The Si surface passivation quality of as-deposited and isothermally annealed samples was compared using photoconductance lifetime measurements in order to calculate their effective surface recombination velocities Seff. A low Seff of 3.9 cm/s (J0s = 24 fA/cm2) is achieved for as-deposited TiCl4-TiO2 at 75 °C when a chemically grown (i.e., from RCA cleaning) SiOx interface layer is present. Depositing TTIP-TiO2 at 200 °C on a chemically grown SiOx interface layer yields equivalent Seff values; however, in this case, TTIP-TiO2 requires a 5–15 min postdeposition forming gas anneal at 250 °C. In contrast, TDMAT-TiO2 was not found to provide a similar level of passivation with/without a chemically grown SiOx interface layer and postdeposition anneal. Modeling of the effective lifetime curves was used to determine the magnitude of the effective charge densities Qf in the TiO2 films. In all cases, Qf was found to be of the order of ∼10^11 q cm−2, meaning field-effect passivation arising from ALD TiO2 is relatively weak. By comparing the material properties of the various TiO2 films using ellipsometry, photothermal deflection spectroscopy, Raman spectroscopy, elastic recoil detection analysis, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, we find experimental support for the role of Cl (in conjunction with hydrogen) playing a beneficial role in passivating dangling bond defects at the Si surface. It is concluded that low deposition temperature TiCl4 processes are advantageous, by providing the lowest Seff without any postanneal and a comparatively high growth per cycle (GPC).

Among the lead-free alternatives currently under research, silver niobate (AgNbO3) is a promising candidate to replace lead-based ceramics in dielectric capacitors for energy storage. Homogeneity and phase-purity of the used thin films are vital for optimal performance of these devices. In this study, a systematic variation of oxygen partial pressure and bias voltage during reactive d.c. magnetron co-sputtering from metallic targets is employed to synthesise AgNbO3 thin films. Structural and chemical composition of the films are investigated using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, elastic recoil detection analysis, and Rutherford backscattering spectrometry. The findings emphasise the necessity of precise parameter control during deposition to avoid the presence of undesirable secondary phases like Ag and Ag2Nb4O11 and to ensure the formation of homogeneous and phase-pure AgNbO3 thin films. The gained insights demonstrate the potential of reactive d.c. magnetron sputtering for the deposition of lead-free AgNbO3 thin films, offering pathways for enhanced environmental compatibility of future dielectric capacitors.

Thermochromic vanadium dioxide (VO2) undergoes a metal-to-semiconductor (MST) transition, a property that can be exploited for energy reduction in buildings in smart windows. We present thermochromic VO2-based films prepared in a roll-to-roll process on ultra-thin glass (0.1 mm) with High Power Impulse Magnetron Sputtering (HiPIMS) without any post annealing. We characterized the film structure with X-ray diffraction, the stoichiometry by Rutherford Backscattering Spectrometry, and the optical properties with spectrophotometry. The selected films (over 2.6 m x 0.3 m), sputtered from a V-metallic tube target doped with 1.2 at.% of W (V-W target), show a transition temperature of 28 °C and 34 °C, a luminous transmittance over 50% and a modulation of the solar energy transmittance of about 7 and 10%. We monitor the deposition control parameters in the roll-to-roll process with optical emission spectroscopy, and show that both the process parameters and target history impact the thermochromic properties. Finally, we extract the charge carrier concentration and mobility by modelling the transmittance and reflectance spectra, which indicates that the VO2-coating has a slight sub-stoichiometric character.

A selection of Late Bronze Age glass objects from the site of Amarna (Egypt) was analysed for their overall chemical composition, colourants and transition metals associated with the sources of cobalt ore. The objects were analysed by means of Particle Induced X-Ray and Gamma-ray Emission and Rutherford Backscattering Spectrometry at the IBC, HZDR, Dresden and the New AGLAE facility, C2RMF, Paris. The data was subsequently compared with further measurements obtained by portable X-Ray Fluorescence (and by Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry) in order to sound the potential of these non-destructive methods to obtain new insights into the production process of glass from Amarna and its provenancing.

A ion beam microprobe is applied for the analysis of friction-induced material transfer processes for ta-C/100Cr6 steel and ta-C/brass friction pairs. Using the appropriate combination of He and H ion beam Rutherford backscattering spectrometry and particle-induced X-ray emission spectrometry, detailed laterally- and depth-resolved information about the element composition of the friction pairs and formation of a tribo layer are obtained. The study shows the formation of a heterogeneously distributed, up to few nm thick surface layer of Fe on the surface of the ta-C coating, and the absence of a carbon transfer layer on the 100Cr6 counter body contact area after the friction treatment in high vacuum. This material combination is responsible for a high coefficient of friction of the order of 0.8. In contrast to that, a homogeneous, sub-nm thick brass transfer layer on the ta-C coating and a C- and O-rich tribolayer were formed in the central contact area of the brass counter body under ambient conditions, resulting in a low friction coefficient of 0.13.

In addition to classical studies comparing composition, structure and functional properties of thin films before and after high-temperature treatments, new approaches towards the correlation of optical properties, composition and structural changes upon annealing are necessary by using in situ techniques. In situ measurements allow the investigation of the materials in real-time under conditions simulating the intended applications, e.g. high temperatures and defined atmospheres. Intra- and interlayer phase transitions, defect generation and annealing, degradation processes, such as element redistribution and interface mixing, as well as material exchange with the environment can have substantial effects on the material’s structure, properties and functionality. All these processes can be studied employing in situ techniques.
In this work, various applications of a cluster tool for depth-resolved compositional, structural and optical characterization of layered materials with thicknesses ranging from sub-nm to 1 μm and for temperatures of -100 to 800 °C are described. [1] The techniques implemented in this setup include Rutherford backscattering spectrometry (RBS), Elastic Recoil Detection (ERD), Raman spectroscopy, Spectroscopic Ellipsometry (SE) and UV-Vis-NIR spectrometry. These in situ techniques allow to identify and to quantify element redistributions, material losses and gains, and the conservation or changes of the optical material properties. Intermixing of the sharp interlayers could also appear at temperatures of up to 800 °C. The onset-temperature of those effects, corresponding to the stability limit, are identified by the in situ measurements. Results of different material systems and processes will be presented including: i) metal-induced crystallization of amorphous carbon in a layer stack of SiO₂/ a-C/ Ni; ii) high-temperature stability tests of a SnO₂:Ta transparent conductive oxide coating [2] and of a WAlSiN-based solar-selective coating [3] as well as iii) diffusion monitoring of an solid-lubricant Ag-rich layer sandwiched between two layers of either TiN or TiSiN.

References

[1] R. Wenisch, F. Lungwitz, D. Hanf, R. Heller, J. Zscharschuch, R. Hübner, J. von Borany, G. Abrasonis, S. Gemming, R. Escobar-Galindo, M. Krause. Anal. Chem. 90 (2018) 7837–7842.
[2] F. Lungwitz, R. Escobar-Galindo, D. Janke, E. Schumann, R. Wenisch, S. Gemming, M. Krause. Sol. Energy Mater. Sol. Cells. 196 (2019) 84–93.
[3] K. Niranjan, M. Krause, F. Lungwitz, F. Munnik, R. Hübner, S. Pramod Pemmasani, R. Escobar Galindo, H. C. Barshilia. Sol. Energy Mater. Sol. Cells. 255 (2023) 112305.

For the improvement of surface roughness, titanium joint arthroplasty (TJA) components are grit-blasted with Al2O3 (corundum) particles during manufacturing. There is an acute concern, particularly with uncemented implants, about polymeric, metallic, and corundum debris generation and accumulation in TJA, and its association with osteolysis and implant loosening. The surface morphology, chemistry, phase analysis, and surface chemistry of retrieved and new Al2O3 grit-blasted titanium alloy were determined with scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and confocal laser fluorescence microscopy, respectively. Peri-prosthetic soft tissue was studied with histopathology. Blasted retrieved and new stems were exposed to human mesenchymal stromal stem cells (BMSCs) for 7 days to test biocompatibility and cytotoxicity. We found metallic particles in the peri-prosthetic soft tissue. Ti6Al7Nb with the residual Al2O3 particles exhibited a low cytotoxic effect while polished titanium and ceramic disks exhibited no cytotoxic effect. None of the tested materials caused cell death or even a zone of inhibition. Our results indicate a possible biological effect of the blasting debris; however, we found no significant toxicity with these materials. Further studies on the optimal size and properties of the blasting particles are indicated for minimizing their adverse biological effects.

Ensuring the biocompatibility of hip implants is essential for the safety, effectiveness, and longevity of these medical devices [1]. The material-induced tissue inflammation and immune reaction must be negligible while promoting tissue integration. However, the major unresolved issue in joint replacement is the occurrence of adverse biological reactions to wear debris, leading to severe inflammation [2] which has been observed at the subcellular level [3]. To gain a deeper understanding of the biocompatibility related to material chemistry and surface topography and to better predict the material functionality and clinical use, it is crucial to investigate the properties of cell adhesion, proliferation, and migration on the implant's surface. In this study, we demonstrate how Al2O3-coated titanium alloys with varying surface topographies and roughness affect the growth and morphology of human bone marrow mesenchymal stromal cells (BM-MSCs). This subcellular-level investigation was conducted on live cells using novel high-resolution 3D confocal fluorescence and backscatter microscopy.

1. Hu CY, Yoon TR. Biomaterials Research, 2018, 22, 33.
2. Cobelli N, Scharf B, Crisi GM, Hardin J, Santambrogio L. Nat Rev Rheumatol. 2011, 7, 600–608.
3. Podlipec R, Punzón-Quijorna E, Pirker L, Kelemen M, Vavpetič P, Kavalar R, Hlawacek G, Štrancar J, Pelicon P, Fokter SK, Materials, 2021, 14, 3048.

Ta3N5 shows great potential as a semiconductor photoanode for solar water splitting. However, its performance is hindered by poor charge carrier transport and trapping due to a high density of defects that introduce electronic states deep within its bandgap. Here, we demonstrate that controlled Ti doping of Ta3N5 can dramatically reduce the concentration of deep-level defects and enhance its photoelectrochemical performance, yielding a sevenfold increase in photocurrent density and a 300 mV cathodic shift in photocurrent onset potential compared to undoped material. Comprehensive characterization reveals that Ti+4 ions substitute Ta+5 lattice sites, thereby introducing compensating acceptor states, reducing concentrations of nitrogen vacancies and reduced Ta+3 states, and thereby suppressing trapping and recombination. Importantly, Ti doping offers distinct advantages compared to Zr, an intensively investigated dopant of Ta3N5 in the same group of the periodic table. Specifically, Ti+4 and Ta+5 have more similar atomic radii, allowing for substitution without introducing lattice strain, and Ti exhibits a lower affinity for oxygen than Zr, enabling its incorporation without increasing the oxygen donor content. Consequently, we demonstrate that the electrical conductivity can be tuned by over seven orders of magnitude. Thus, Ti doping in Ta3N5 provides a powerful basis for precisely engineering the optoelectronic characteristics of Ta3N5 and to substantially improve its functional characteristics as an advanced photoelectrode for solar fuels applications.

Hard coatings of a few micrometre thickness are often used to extend the lifespan of machining tools and components for, e.g., automotive and aerospace applications [1]. A further increase of the lifespan of these tools and components can be achieved by making so-called self-lubricant coatings. They make use of self-adaptive mechanisms that can lead to a protective tribolayer as a solid lubricant [2]. Self-lubrication can be achieved by the incorporation of noble metals like silver in hard matrices. When applied in this way, silver can diffuse to the surface and act as a solid lubricant. However, these benefits are limited in time as the silver is released and is quickly depleted from the coating.
The fast depletion of silver can be reduced by encapsulating it in a dense barrier sandwich layer [3]. In this presentation, the diffusion of silver in two hard matrices (TiN and TiSiN) is studied during annealing by in-situ Rutherford Backscattering Spectrometry (RBS) using the cluster tool at HZDR [4]. Samples were annealed at 600°C and 800°C for two hours with continuous monitoring by RBS measurements. These show changes in the elemental distribution during and after annealing as a function of sandwich type and microstructure. The results are part of a larger study to understand the effect of microstructure of hard coatings on the diffusion behaviour of silver, which also includes Transmission Election Microscopy measurements [5].

References
[1] P.H. Mayrhofer, C. Mitterer, L. Hultman, H. Clemens, Microstructural design of hard coatings, Progress in Materials Science 51 (2006) 1032-1114, 10.1016/j.pmatsci.2006.02.002
[2] A.A. Voevodin, C. Muratore, S.M. Aouadi, Hard coatings with high temperature adaptive lubrication and contact thermal management: review, Surf. Coat. Technol. 257 (2014) 247–265, 10.1016/j.surfcoat.2014.04.046
[3] D. Cavaleiro, D. Figueiredo, C.W. Moura, A. Cavaleiro, S. Carvalho, F. Fernandes, Machining performance of TiSiN(Ag) coated tools during dry turning of TiAl6V4 aerospace alloy, Ceram. Int. 47 (2021) 11799–11806, 10.1016/j.ceramint.2021.01.021
[4] R. Wenisch et al., Cluster Tool for In Situ Processing and Comprehensive Characterization of Thin Films at High Temperatures, Anal. Chem. 90 (2018) 7837-7842, 10.1021/acs.analchem.8b00923
[5] D. Cavaleiro, F. Munnik, M. Krause, E. Carbo-Argibay, P.J. Ferreira, A. Cavaleiro, F. Fernandes, The role of interfaces and morphology on silver diffusion in hard coatings, Surfaces and Interfaces 41 (2023) 103182, 10.1016/j.surfin.2023.103182

Pulsed filtered cathodic arc deposition involves formation of energetic multiply charged metal ions, which help to form dense, adherent, and macroparticle-free thin films. Ions possess not only significant kinetic energy, but also potential energy primarily due to their charge, which for cathodic arc plasmas is usually greater than one. While the effects of kinetic ion energy on the growing film are well investigated, the effects of the ions’ potential energy are less known. In the present work, we make a step towards decoupling the contributions of kinetic and potential energies of ions on thin film formation. The potential energy is changed by enhancing the ion charge states via using an external magnetic field at the plasma source. The kinetic energy is adjusted by biasing the arc source (“plasma bias”), which allows us to approximately compensate the differences in kinetic energy while the substrate and ion energy detector remain at ground. However, application of an external magnetic field also leads to an enhancement of the ion flux and hence the desired complete decoupling of the potential and kinetic energy effects will require further steps. Charge-state-resolved energy distribution functions of ions are measured at the substrate position for different arc source configurations, and thin films are deposited using exactly those configurations. Detailed characterization of the deposited thin films is performed to reveal the correlations of changes in structure with kinetic and potential energies of multiply charged ions. It is
observed that the cathode composition (Al:V ratio) strongly affects the formation of the thermodynamically stable wurtzite or the metastable cubic phase. The external magnetic field applied at the arc source is found to greatly alter the plasma and therefore to be the primary, easily accessible
“tuning knob” to enhance film crystallinity. The effect of “atomic scale heating” provided by the ions’ kinetic and potential energies on the film crystallinity is investigated, and the possibility to deposit crystalline (V,Al)N films without substrate heating is demonstrated. This study shows an approach towards
distinguishing the contributions stemming from kinetic and potential energies of ions on the film growth, however, further research is needed to assess and distinguish the additional effect of ion flux intensity (current).

Molybdenum disulfide (MoS2) few-layer films have gained considerable attention for their possible applications in electronics, optics, and also as a promising material for energy conversion and storage. Intercalating alkali metals, like lithium, offers the opportunity to engineer the electronic properties of MoS2. However, the influence of lithium on the growth of MoS2 layers has not been fully explored. Here, we have studied how lithium affects the structural and optical properties of the MoS2 few-layer films prepared using a new method based on one-zone sulfurization with Li2S as a source of the lithium. This method enables incorporation of Li into octahedral and tetrahedral sites of the already prepared MoS2 films or during the MoS2 formation. Our results discover an important effect of lithium promoting the epitaxial growth and horizontal alignment of the films. Moreover, we have observed a vertical-to-horizontal reorientation in vertically aligned MoS2 films upon lithiation. The measurements show long-term stability and preserved chemical composition of the horizontally aligned Li-doped MoS2.

Color centers in hexagonal boron nitride (hBN) have been emerging as a multifunctional platform for various optical applications including quantum information processing, quantum computing and imaging. Simultaneously, due to its biocompatibility and biodegradability hBN is a promising material for biomedical applications. In this work, we demonstrate single-photon emission from hBN color centers embedded inside live cells and their application to cellular barcoding. The generation and internalization of multiple color centers into cells was performed via simple and scalable procedure while keeping the cells unharmed. The emission from live cells was observed as multiple diffraction-limited spots, which exhibited excellent single-photon characteristics with high single-photon purity of 0.1 and superb mission stability without photobleaching or spectral shifts over several hours. Due to different emission wavelengths and peak widths of the color centers, they were employed as barcodes. Each color center can exist in one out of 470 possible distinguishable states and a combination of a few color centers per cell can be used to uniquely tag virtually an unlimited number of cells. This barcoding technique is superior to others in almost all respects, including ease of production by a single-step procedure, biocompatibility and biodegradability, emission stability, no photobleaching, small size and a huge number of unique barcodes. This work provides a basis for the use of hBN color centers for robust barcoding of cells and due to the single photon emission, presented concepts could in future be extended to quantum-limited sensing and super-resolution imaging.

The heaviest elements can exclusively be produced in actinide-target based nuclear fusion reactions with intense heavy-ion beams. Ever more powerful accelerators deliver beams of continuously increasing intensity, which brings targets of current technology to their limits and beyond. We motivate efforts to produce targets with improved properties, which calls for a better understanding of targets produced by molecular plating, the current standard method. Complementary analytical methods will help shedding more light on their chemical and physical changes in the beam. Special emphasis is devoted to the aspect of the optimum target thickness and the choice of the backing material.