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Granular metals (GMs), consisting of metal nanoparticles separated by an insulating matrix, frequently serve as a platform for fundamental electron transport studies. However, few technologically mature devices incorporating GMs have been realized, in large part because intrinsic defects (e.g., electron trapping sites and metal/insulator interfacial defects) frequently impede electron transport, particularly in GMs that do not contain noble metals. Here, we demonstrate that such defects can be minimized in molybdenum–silicon nitride (Mo–SiNx) GMs via optimization of the sputter deposition atmosphere. For Mo–SiNx GMs deposited in a mixed Ar/N2 environment, x-ray photoemission spectroscopy shows a 40%–60% reduction of interfacial Mo-silicide defects compared to Mo–SiNx GMs sputtered in a pure Ar environment. Electron transport measurements confirm the reduced defect density; the dc conductivity improved (decreased) by 104–105 and the activation energy for variable-range hopping increased 10×. Since GMs are disordered materials, the GM nanostructure should, theoretically, support a universal power law (UPL) response; in practice, that response is generally overwhelmed by resistive (defective) transport. Here, the defect-minimized Mo–SiNx GMs display a superlinear UPL response, which we quantify as the ratio of the conductivity at 1 MHz to that at dc, Δ σ ω. Remarkably, these GMs display a Δ σ ω up to 107, a three-orders-of-magnitude improved response than previously reported for GMs. By enabling high-performance electric transport with a non-noble metal GM, this work represents an important step toward both new fundamental UPL research and scalable, mature GM device applications. [ABSTRACT FROM AUTHOR]

Deposition of epitaxial oxide semiconductor films using physical vapor deposition methods requires a detailed understanding of the role of energetic particles to control and optimize the film properties. In the present study, Ga 2 O 3 thin films are heteroepitaxially grown on Al 2 O 3 (0001) substrates using oxygen ion beam sputter deposition. The influence of the following relevant process parameters on the properties of the thin films is investigated: substrate temperature, oxygen background pressure, energy of primary ions, ion beam current, and sputtering geometry. The kinetic energy distributions of ions in the film-forming flux are measured using an energy-selective mass spectrometer, and the resulting films are characterized regarding crystalline structure, microstructure, surface roughness, mass density, and growth rate. The energetic impact of film-forming particles on the thin film structure is analyzed, and a noticeable decrease in crystalline quality is observed above the average energy of film-forming Ga + ions around 40 eV for the films grown at a substrate temperature of 725 ° C. [ABSTRACT FROM AUTHOR]

Ferroelectric properties of hafnium-based thin films have gained significant interest, yet the fundamental mechanisms responsible for the emergence of the ferroelectric phase continue to be inadequately investigated. In contrast with polycrystalline films fabricated by atomic layer deposition or sputter methods, which possess uncertainty in polarization orientation, epitaxial ferroelectric HfO2-based materials are less investigated, especially for factors such as electric field and oxygen vacancy, which are proposed and examined for their potential impacts on phase stability. In this study, Y-doped hafnium oxide (HYO) ferroelectric epitaxial films were fabricated using pulsed laser deposition, with variations in oxygen pressure during the deposition process. Structural and electrical analyses of HYO epitaxial ferroelectric films prepared under differing oxygen pressures revealed a correlation between the ferroelectric properties of the films and the oxygen content. An optimal selection of oxygen pressure was found to be conducive to the formation of HYO epitaxial ferroelectric films, presenting a promising avenue for future ferroelectric memory applications. [ABSTRACT FROM AUTHOR]

Ferroelectric properties of hafnium-based thin films have gained significant interest, yet the fundamental mechanisms responsible for the emergence of the ferroelectric phase continue to be inadequately investigated. In contrast with polycrystalline films fabricated by atomic layer deposition or sputter methods, which possess uncertainty in polarization orientation, epitaxial ferroelectric HfO2-based materials are less investigated, especially for factors such as electric field and oxygen vacancy, which are proposed and examined for their potential impacts on phase stability. In this study, Y-doped hafnium oxide (HYO) ferroelectric epitaxial films were fabricated using pulsed laser deposition, with variations in oxygen pressure during the deposition process. Structural and electrical analyses of HYO epitaxial ferroelectric films prepared under differing oxygen pressures revealed a correlation between the ferroelectric properties of the films and the oxygen content. An optimal selection of oxygen pressure was found to be conducive to the formation of HYO epitaxial ferroelectric films, presenting a promising avenue for future ferroelectric memory applications. [ABSTRACT FROM AUTHOR]

This work outlines conditions suitable for the heteroepitaxial growth of Cr2O3(0001) films (1.5–20 nm thick) on a Ru(0001)-terminated substrate. Optimized growth is achieved by sputter deposition of Cr within a 4 mTorr Ar/O2 20% ambient at Ru temperatures ranging from 450 to 600 °C. The Cr2O3 film adopts a 30° rotated honeycomb configuration with respect to the underlying Ru(0001) substrate and exhibits a hexagonal lattice parameter consistent with that for bulk Cr2O3(0001). Heating to 700 °C within the same environment during film preparation leads to Ru oxidation. Exposure to temperatures at or above 400 °C in a vacuum, Ar, or Ar/H2 3% leads to chromia film degradation characterized by increased Ru 3d XPS intensity coupled with concomitant Cr 2p and O 1s peak attenuations when compared to data collected from unannealed films. An ill-defined but hexagonally well-ordered RuxCryOz surface structure is noted after heating the film in this manner. Heating within a wet Ar/H2 3% environment preserves the Cr2O3(0001)/Ru(0001) heterolayer structure to temperatures of at least 950 °C. Heating an Ru–Cr2O3–Ru heterostacked film to 950 °C within this environment is shown by cross-sectional scanning/transmission electron microscopy (S/TEM) to provide clear evidence of retained epitaxial bicrystalline oxide interlayer structure, interlayer immiscibility, and epitaxial registry between the top and bottom Ru layers. Subtle effects marked by O enrichment and O 1s and Cr 2p shifts to increased binding energies are noted by XPS in the near-Ru regions of Cr2O3(0001)/Ru(0001) and Ru(0001)/Cr2O3(0001)/Ru(0001) films after annealing to different temperatures in different sets of environmental conditions. [ABSTRACT FROM AUTHOR]

This work investigates the physical properties of Al1−xScxN thin films sputtered at low temperatures by varying the process conditions. Specifically, the films were deposited at room temperature by applying a radio frequency power equal to 150 W to an AlSc alloy (60:40) target, varying the nitrogen flux percentage in the (Ar + N2) sputtering atmosphere (30%, 40%, 50%, and 60%) and keeping constant the working pressure at 5 × 10−3 mbar. The structural and chemical properties of the Al1−xScxN films were studied by x-ray diffraction and Rutherford backscattering spectrometry techniques, respectively. The piezoelectric response was investigated by piezoresponse force microscopy. In addition, the surface potential was evaluated for the first time for Sc-doped AlN thin films by Kelvin probe force microscopy, providing piezoelectric coefficients free from the no-piezoelectric additional effect to the mechanical deformation, i.e., the electrostatic force. By alloying AlN with scandium, the piezoelectric response was strongly enhanced (up to 200% compared to undoped AlN), despite the low deposition temperature and the absence of any other additional energy source supplied to the adatoms during thin film growth, which generally promotes a better structural arrangement of polycrystalline film. This is a strategic result in the field of microelectromechanical systems completely fabricated at low temperatures. [ABSTRACT FROM AUTHOR]

Sputter deposition of ultrathick (≈ 20 μ m) Au–Ta alloy coatings on sphero-cylindrical substrates is key for the fabrication of hohlraums for magnetically assisted inertial confinement fusion. Here, we study the deposition of AuTa 4 alloy coatings onto rotating substrates. We use high-power impulse magnetron sputtering (HiPIMS) in a constant peak target voltage mode. Results show that the target erosion state has a strong impact on the dominant crystallographic phase, microstructure, surface morphology, and electrical resistivity of AuTa 4 films. This is due to effects of changes in the confining magnetic field with target erosion on the HiPIMS discharge characteristics and the sputter source output. We quantify these effects via plasma diagnostics and discuss the optimization of HiPIMS deposition of ultrathick films for cases when target erosion effects dominate film properties. [ABSTRACT FROM AUTHOR]

In this study, we developed a hybrid machine learning technique by combining appropriate classification and regression models to address challenges in producing high-mobility amorphous In2O3:Sn (a-ITO) films, which were fabricated by radio-frequency magnetron sputtering with a nitrogen-mediated amorphization method. To overcome this challenge, this hybrid model that was consisted of a support vector machine as a classification model and a gradient boosting regression tree as a regression model predicted the boundary conditions of crystallinity and experimental conditions with high mobility for a-ITO films. Based on this model, we were able to identify the boundary conditions between amorphous and crystalline crystallinity and thin film deposition conditions that resulted in a-ITO films with 27% higher mobility near the boundary than previous research results. Thus, this prediction model identified key parameters and optimal sputtering conditions necessary for producing high-mobility a-ITO films. The identification of such boundary conditions through machine learning is crucial in the exploration of thin film properties and enables the development of high-throughput experimental designs. [ABSTRACT FROM AUTHOR]

The epitaxial growth of heavily Ge‐doped GaN films using pulsed sputtering deposition (PSD) on AlN (0001)/sapphire substrates is presented and the correlations among their structural, electrical, and optical properties are investigated. High‐quality Ge‐doped PSD‐GaN films are grown with electron concentrations of 0.33–4.4 × 1020 cm−3. Notably, cathode luminescence spectra reveal the absence of defect‐induced emissions associated with Ga vacancies (2.3–2.4 eV), consistent with the high electron mobilities of the films. As the electron concentration increases, the optical bandgap also increases. This correlation can be explained by combining the theoretical formulas for the Burstein–Moss shift and the bandgap renormalization effects. Remarkably, the optical bandgap reaches 3.84 eV at 4.4 × 1020 cm−3 carrier concentration, marking the highest value reported for the optical bandgap of GaN. These results indicate the potential of heavy Ge doping in GaN via PSD for applications in highly transparent conductive layers and tunneling junctions within GaN‐based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Herein, the temperature‐dependent characteristics of AlN/Al0.5Ga0.5N high electron mobility transistors (HEMTs) with highly degenerate n‐type GaN (d‐GaN) ohmic contacts fabricated via pulsed sputtering deposition (PSD) are investigated. The ohmic contacts formed at the source and drain regions demonstrate low resistivity within the temperature range of 77–473 K. It is found that the temperature dependence of the contact resistance (RC) for the AlN/Al0.5Ga0.5N HEMTs with regrowth d‐GaN contacts is attributable to the energy barrier induced by the Fermi level difference between the d‐GaN contacts and Al0.5Ga0.5N channel layer. Notably, the RC between the d‐GaN contacts and the channel layer is 1.4 and 0.15 Ω mm at 77 and 473 K, respectively. Temperature‐dependent device on‐resistance coincides with the temperature variation of the two‐dimensional electron gas sheet resistance because the contact resistance is negligibly low in the studied temperature range. Moreover, AlN/Al0.5Ga0.5N HEMTs with d‐GaN contacts exhibit excellent switching characteristics, achieving an ION/IOFF ratio of ≈106, even at high temperatures up to 473 K. The results indicate that the PSD d‐GaN contact technique has potential to overcome the limitations of ohmic contacts for high Al‐composition AlGaN electronic devices, especially for next‐generation high‐power‐density radio frequency transistors operating at high temperatures. [ABSTRACT FROM AUTHOR]

Interfacial bond formation during sputter deposition of metal‐oxide thin films onto polycarbonate (PC) is investigated by ab initio molecular dynamics simulations and X‐ray photoelectron spectroscopy (XPS) analysis of PC|X interfaces (X = Al2O3, TiO2, TiAlO2). Generally, the predicted bond formation is consistent with the experimental data. For all three interfaces, the majority of bonds identified by XPS are (C─O)─metal bonds, whereas C─metal bonds are the minority. Compared to the PC|Al2O3 interface, the PC|TiO2 and PC|TiAlO2 interfaces exhibit a reduction in the measured interfacial bond density by 75 and ∼65%, respectively. Multiplying the predicted bond strength with the corresponding experimentally determined interfacial bond density shows that Al2O3 exhibits the strongest interface with PC, while TiO2 and TiAlO2 exhibit ∼70 and ∼60% weaker interfaces, respectively. This can be understood by considering the complex interplay between the metal‐oxide composition, the bond strength, and the population of bonds formed across the interface. [ABSTRACT FROM AUTHOR]

AbstractHigh Platinum loading levels in fuel cells may ensure better durability and catalytic activity but increases fuel cells’ cost, thereby hindering large-scale commercialization. The use of non-precious catalysts may seem like a lucrative solution, but they cannot substitute platinum completely. Hence, the focus should also be given to alternate fabrication methods of the catalyst layer that will achieve ultra-low platinum loadings. Some of the methods are modified thin film method, electrodeposition, sputter deposition method, dual ion beam assisted deposition, and electroless deposition. Nano carbons as catalyst support can also be given priority as they aid the catalyst with mechanical properties. Each method is compared, reflecting the inherent advantages and disadvantages. Finally, the sputter deposition method was chosen as the most promising method in the current state of technology and research. A computational fluid dynamics simulation of a fuel cell using the sputter deposition method was performed which showed high power utilization thereby validating the benefits of the method. [ABSTRACT FROM AUTHOR]

Background: By the end of 2050, it is expected that 68% of the population will live in urban areas. A higher density of people living in cities generates an increased urban heat island. Radiative cooling (RC) materials are proposed as a key strategy to mitigate global warming and urban heating. The Horizon 2020 project MIRACLE aims at developing a new RC material based on conventional concrete. This paper presents a framework developed for comparing both the cradle-to-gate environmental impact and cooling potential of the newly developed photonic meta-concrete (or any other new RC material) with existing RC materials. The framework is applied to various RC materials using the generic Ecoinvent v3.6 database. The impact assessment method is in line with the Belgian life cycle assessment method for buildings and covers the 15 environmental impact categories of the EN15804:A2. The cooling performance is assessed by implementing the material spectral emissivity into a thermal model for Brussels and Madrid. Results: The study shows that the sputtering process contributes over 75% to the cradle-to-gate environmental impact of several RC materials, while materials produced without this process, have significantly lower impacts. The assessment of the cooling potential showed that convection heat gains make it difficult to create an all-year round cooling material. The comparison with a conventional building material, a concrete roof tile, hence shows great potential for these RC materials as heating gains during summer are significantly reduced. Analysing cooling performance alongside environmental impact, the study identified two RC materials, i.e. D6 and D10, as the most preferred in both Brussels and Madrid, considering their lower environmental impact and superior performance. Conclusions: The literature review revealed that a standardised way to assess and benchmark RC materials based on their cradle-to-gate environmental impact and cooling performance is lacking to date. This paper hence presents, for the first time, a method to compare RC materials considering these two characteristics. This method allows to identify the most competitive RC materials, which will serve in our study to benchmark the newly developed photonic meta-concrete. [ABSTRACT FROM AUTHOR]

Cadmium telluride is an efficient light absorbing material successfully used in solar cell technology. The efficiency of such photovoltaic devices is strongly dependent on post‐deposition thermal treatments in the presence of chlorine. The benefits of this process on the absorbing layer include removal of intragrain defects, grain growth enhancement, and grain boundaries passivation. The absorber chlorination is a crucial step for which CdCl2 is the most common choice. Its use, however, has been overshadowed by the toxicity of Cd‐ and Cl‐containing vapors and residues. In this work, chlorine was incorporated in CdTe films during growth using sputtering targets with different chloride compounds: CdCl2, TeCl4, BaCl2, CaCl2, or LiCl. After characterizing these films, CdTe:CdCl2 and CdTe:TeCl4 were selected as feasible absorbers for testing their performance in photovoltaic devices. Efficiencies near 7% were obtained in as‐grown unoptimized cells in which the absorber consisted of two layers: pristine CdTe and CdTe:CdCl2 or CdTe:TeCl4. The chlorinated layers acted as Cl sources for the adjacent CdTe and CdS, which produced a homogeneous distribution of chlorine throughout the cell. In the during‐growth activating‐layer (DG‐AL) method used here, the chlorine diffusion during growth had a doping effect, passivated grain boundaries and defects, improved the back contact characteristics by reducing the CdTe work function, and lowered the pinhole formation probability by producing a compact chlorinated CdTe layer. [ABSTRACT FROM AUTHOR]

[Display omitted] To understand the complex interplay of topography and surface chemistry in wetting, fundamental studies investigating both parameters are needed. Due to the sensitivity of wetting to miniscule changes in one of the parameters it is imperative to precisely control the experimental approach. A profound understanding of their influence on wetting facilitates a tailored design of surfaces with unique functionality. We present a multi-step study: The influence of surface chemistry is analyzed by determining the adsorption of volatile carbonous species (A) and by sputter deposition of metallic copper and copper oxides on flat copper substrates (B). A precise surface topography is created by laser processing. Isotropic topography is created by ps laser processing (C), and hierarchical anisotropic line patterns are produced by direct laser interference patterning (DLIP) with different pulse durations (D). Our results reveal that the long-term wetting response of polished copper surfaces stabilizes with time despite ongoing accumulation of hydrocarbons and is dominated by this adsorption layer over the oxide state of the substrate (Cu, CuO, Cu 2 O). The surfaces' wetting response can be precisely tuned by tailoring the topography via laser processing. The sub-pattern morphology of primary line-like patterns showed great impact on the static contact angle, wetting anisotropy, and water adhesion. An increased roughness inside the pattern valleys combined with a minor roughness on pattern peaks favors air-inclusions, isotropic hydrophobicity, and low water adhesion. Increasing depth of the primary topography can also induce air-inclusions despite increasing peak roughness while time dependent wetting transitions were observed. [ABSTRACT FROM AUTHOR]

The development of tandem photovoltaics and photoelectrochemical solar cells requires new absorber materials with bandgaps in the range of ≈1.5–2.3 eV, for use in the top cell paired with a narrower‐gap bottom cell. An outstanding challenge is finding materials with suitable optoelectronic and defect properties, good operational stability, and synthesis conditions that preserve underlying device layers. This study demonstrates the Zintl phosphide compound CaZn2P2 as a compelling candidate semiconductor for these applications. Phase‐pure, ≈500 nm‐thick CaZn2P2 thin films are prepared using a scalable reactive sputter deposition process at growth temperatures as low as 100 °C, which is desirable for device integration. Ultraviolet‐visible  spectroscopy shows that CaZn2P2 films exhibit an optical absorptivity of ≈104 cm−1 at ≈1.95 eV direct bandgap. Room‐temperature photoluminescence (PL) measurements show near‐band‐edge optical emission, and time‐resolved microwave conductivity (TRMC) measurements indicate a photoexcited carrier lifetime of ≈30 ns. CaZn2P2 is highly stable in both ambient conditions and moisture, as evidenced by PL and TRMC measurements. Experimental data are supported by first‐principles calculations, which indicate the absence of low‐formation‐energy, deep intrinsic defects. Overall, this study shall motivate future work integrating this potential top cell absorber material into tandem solar cells. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) is one of the most versatile semiconductor materials with many potential applications. Understanding the interactions between the surface chemistry of ZnO along with its physico-chemical properties are essential for the development of ZnO as a robust photocatalyst for the removal of aqueous pollutants. We report on the fabrication of nanoparticle-like porous ZnO films and the correlation between the fabrication process parameters, particle size, surface oxygen vacancies (SOV), photoluminescence and photocatalytic performance. The synthesis route is unique, as highly porous zinc layers with nanoscale grains were first grown via magnetron sputtering, a vacuum-based technique, and subsequently annealed at temperatures of 400 °C, 600 °C and 800 °C in oxygen flow to oxidise them to zinc oxide (ZnO) while maintaining their porosity. Our results show that as the annealing temperature increases, nanoparticle agglomeration increases, and thus there is a decrease in the active sites for the photocatalytic reaction. However, for selected samples the annealing leads to an increase of the photocatalytic efficiency, which we explain based on the analysis of defects in the material, based on photoluminescence (PL). PL analysis showed that in the material the transition between the conduction band and the oxygen vacancy is responsible for the green emission centered at 525 nm, but the photocatalytic activity correlated best with surface states—related emission. [ABSTRACT FROM AUTHOR]

As a first step toward developing a downsized and high-performance O2 separator suitable for large-scale industrial applications, such as steelmaking, we have studied nanocrystalline Ag alloy thin films with high O2 permeability via rapid diffusion at Ag grain boundaries, operating at plant-waste heat temperatures (200 °C to 500 °C). In the present study, fabrication of nanocrystalline Ag–2at. pctCu–10at. pctAl alloy thin films with Ag grain size below 10 nm was attempted via reactive sputtering in Ar–O2 using grain boundary pinning force of a large number of alumina particles. Cross-sectional observation of the fabricated thin film showed that the Ag grain size ranged from 4 to 15 nm when the film thickness was less than 200 nm, but when the film thickness exceeded 200 nm, the Ag grains abruptly coarsened, reaching a maximum grain size of 214 nm. Furthermore, large surface irregularities with sizes of up to 500 to 600 nm (equivalent to 2/3 of the film thickness) were also observed. Heat transfer analysis revealed that the Ag film partially melted because of the large amount of heat released by the oxidation of Al during sputtering deposition. The conditions necessary for the fabrication of high-Al nanocrystalline Ag alloy thin films via reactive sputtering in Ar–O2 gas without film melting were clarified. [ABSTRACT FROM AUTHOR]

Plasma discharge pulse length (tPLength) was investigated for its impact on the crystallinity of GaN films deposited on a sapphire substrate using a high-density convergent plasma sputtering device (CPSD). The study covered tPLength values from 1 to 200 ms, maintaining the substrate temperature at 200 °C. GaN films showed preferential orientation along the (0002) plane for all tPLength settings. X-ray diffraction analysis revealed a heteroepitaxial-like growth pattern with a sixfold symmetric diffraction pattern corresponding to GaN{10−10} planes. At a tPLength of 200 ms, the full width at half maximum of the rocking curve at GaN (0002) diffraction angle decreased to 1.6°. Optimizing the deposition rate per plasma discharge pulse with CPSD indicated the importance of selecting an optimal tPLength for achieving desirable crystalline properties in GaN film sputtering deposition. [ABSTRACT FROM AUTHOR]

Abstract Background By the end of 2050, it is expected that 68% of the population will live in urban areas. A higher density of people living in cities generates an increased urban heat island. Radiative cooling (RC) materials are proposed as a key strategy to mitigate global warming and urban heating. The Horizon 2020 project MIRACLE aims at developing a new RC material based on conventional concrete. This paper presents a framework developed for comparing both the cradle-to-gate environmental impact and cooling potential of the newly developed photonic meta-concrete (or any other new RC material) with existing RC materials. The framework is applied to various RC materials using the generic Ecoinvent v3.6 database. The impact assessment method is in line with the Belgian life cycle assessment method for buildings and covers the 15 environmental impact categories of the EN15804:A2. The cooling performance is assessed by implementing the material spectral emissivity into a thermal model for Brussels and Madrid. Results The study shows that the sputtering process contributes over 75% to the cradle-to-gate environmental impact of several RC materials, while materials produced without this process, have significantly lower impacts. The assessment of the cooling potential showed that convection heat gains make it difficult to create an all-year round cooling material. The comparison with a conventional building material, a concrete roof tile, hence shows great potential for these RC materials as heating gains during summer are significantly reduced. Analysing cooling performance alongside environmental impact, the study identified two RC materials, i.e. D6 and D10, as the most preferred in both Brussels and Madrid, considering their lower environmental impact and superior performance. Conclusions The literature review revealed that a standardised way to assess and benchmark RC materials based on their cradle-to-gate environmental impact and cooling performance is lacking to date. This paper hence presents, for the first time, a method to compare RC materials considering these two characteristics. This method allows to identify the most competitive RC materials, which will serve in our study to benchmark the newly developed photonic meta-concrete.

Zinc oxide (ZnO) is one of the most versatile semiconductor materials with many potential applications. Understanding the interactions between the surface chemistry of ZnO along with its physico-chemical properties are essential for the development of ZnO as a robust photocatalyst for the removal of aqueous pollutants. We report on the fabrication of nanoparticle-like porous ZnO films and the correlation between the fabrication process parameters, particle size, surface oxygen vacancies (SOV), photoluminescence and photocatalytic performance. The synthesis route is unique, as highly porous zinc layers with nanoscale grains were first grown via magnetron sputtering, a vacuum-based technique, and subsequently annealed at temperatures of 400 °C, 600 °C and 800 °C in oxygen flow to oxidise them to zinc oxide (ZnO) while maintaining their porosity. Our results show that as the annealing temperature increases, nanoparticle agglomeration increases, and thus there is a decrease in the active sites for the photocatalytic reaction. However, for selected samples the annealing leads to an increase of the photocatalytic efficiency, which we explain based on the analysis of defects in the material, based on photoluminescence (PL). PL analysis showed that in the material the transition between the conduction band and the oxygen vacancy is responsible for the green emission centered at 525 nm, but the photocatalytic activity correlated best with surface states—related emission.

We report the impact of flash-lamp-annealing (FLA) on the structural evolution of amorphous titania (TiO 2) films produced by DC reactive magnetron sputtering. TiO 2 films were grown at room-temperature at different oxygen partial pressure (P O2) and subsequently annealed as a function of the FLA energy density. X-ray diffraction confirms that FLA induces phase formation from the initial amorphous state with a general transition from anatase to rutile by increasing the FLA energy density (temperature). Interestingly, the transformation onset of anatase to rutile is achieved at lower energy densities for higher P O2. On the contrary, films with a highly resilient anatase phase can be produced at relatively low P O2. A detailed analysis of the pristine amorphous structure carried out by X-ray absorption near-edge structure indicates the role of oxygen sites in the observed phase transformation. In particular, oxygen vacancies seem to stabilize the anatase phase at high temperatures. The results show the relevance of subtle changes in the initial amorphous structure for phase selectivity in TiO 2 films upon FLA. [ABSTRACT FROM AUTHOR]

Co–Mo alloy clusters with extended solubility of Mo in hcp Co were produced by inert gas condensation (IGC). While the equilibrium solubility of Mo in hexagonal close-packed (hcp) Co is on the order of 1 atomic percent, the non-equilibrium aspects of IGC resulted in ~ 18 atomic percent Mo dissolved in hcp Co. The extended solid solutions and hcp structure were observed across all of the processing conditions, which included variation of sputtering power and aperture size. There was, however, variation of nanoparticle size and magnetic behavior with processing parameters. The Co(Mo) nanoparticles were ferromagnetic at room temperature. Coercivities of the nanoparticles produced with a 2.5-mm aperture were independent of sputtering power and significantly higher than those of the nanoparticles produced with a 7-mm aperture. The coercivities of the nanoparticles produced with a 7-mm aperture were slightly power-dependent. Overall, there appeared to be a relationship between coercivity and nanoparticle size. [ABSTRACT FROM AUTHOR]

This study introduces silicon substrates with a switchable magnetic contrast layer (MCL) for polarized neutron reflectometry (PNR) experiments at the solid–liquid interface to study soft‐matter surface layers. During standard neutron reflectometry (NR) experiments on soft‐matter samples, structural and compositional information is obtained by collecting experimental data with different isotopic contrasts on the same sample. This approach is normally referred to as contrast matching, and it can be achieved by using solvents with different isotopic contrast, e.g. different H2O/D2O ratios, and/or by selective deuteration of the molecules. However, some soft‐matter systems might be perturbed by this approach, or it might be difficult to implement, particularly in the case of biological samples. In these scenarios, solid substrates with an MCL are an appealing alternative, as the magnetic contrast with the substrate can be used for partial recovery of information on the sample structure. More specifically, in this study, a magnetically soft Fe layer coated with SiO2 was produced by ion‐beam sputter deposition on silicon substrates of different sizes. The structure was evaluated using X‐ray reflectometry, atomic force microscopy, vibrating sample magnetometry and PNR. The collected data showed the high quality and repeatability of the MCL parameters, regardless of the substrate size or the thickness of the capping SiO2 layer. Previously proposed substrates with an iron MCL used an Au capping layer. The SiO2 capping layer proposed here allows reproduction of the typical surface of a standard silicon substrate used for NR experiments and is compatible with a large variety of soft‐matter samples. This application is demonstrated with ready‐to‐use 50 × 50 × 10 mm substrates in PNR experiments for the characterization of a lipid bilayer in a single solvent contrast. Overall, the article highlights the potential of PNR with an MCL for the investigation of soft‐matter samples. [ABSTRACT FROM AUTHOR]

This study aims to evaluate and compare the properties of a biomedical clinically established zirconium nitride (ZrN) multilayer coating prepared using two different techniques: pulsed magnetron sputtering and cathodic arc deposition. The investigation focuses on the crystalline structure, grain size, in-vitro oxidation behaviour and tribological performance of these two coating techniques. Experimental findings demonstrate that the sputter deposition process resulted in a distinct crystalline structure and smaller grain size compared to the arc deposition process. Furthermore, in vitro oxidation caused oxygen to penetrate the surface of the sputtered ZrN top layer to a depth of 700 nm compared to 280 nm in the case of the arc-deposited coating. Finally, tribological testing revealed the improved wear rate of the ZrN multilayer coating applied by sputter deposition. [ABSTRACT FROM AUTHOR]

The unique mechanical properties of Tungsten Carbide (WC), such as fracture toughness, exceptional hardness, high melting temperature, outstanding thermal stability, anti-oxidation qualities fatigue and creep resistance, have made it a suitable industrial material for different applications. It is also considered to be a promising material for coating on plasma-facing walls in a Tokamak reactor. The aim of the present work is to study the effect of varying substrate temperature, concentration of tungsten (W) and annealing in the structural properties of WC films. The WC films are deposited on a silicon substrate at different substrate temperatures viz. RT (300 K), 400, 500, 600 and 700 K using DC magnetron sputtering. W-rich WC films were deposited keeping the power of WC constant (100 Watt) and varying W powers (10 Watt, 20 Watt, 30 Watt, 40 Watt) at room temperature. Later, these W-rich WC films were annealed at 800°C in a reducing atmosphere. Glancing incidence X-ray diffraction (GIXRD) and Raman spectroscopy of the films are performed for structural analysis. GIXRD of the WC films reveals that as-deposited RT films are amorphous. However, films which are either deposited at elevated substrate temperature or are annealed are crystalline. This is confirmed by Raman's measurements. It also indicates the presence of disorder and nanocrystalline phases due to temperature variations. [ABSTRACT FROM AUTHOR]

Many thin film applications are based on oxides. The optimization of the oxide properties is an on-going process and requires a deep understanding of the deposition process. A typical feature of reactive (magnetron) sputter deposition is the presence of negative oxygen ions. Two groups of ions can be identified based on their energy. Low energy ions are generated in the bulk of the discharge. The high energy ions are emitted from the oxide or oxidized target surface. As these ions are generated at the cathode, they are accelerated by the electric field toward the growing film. Depending on the discharge voltage and the powering method, their energy is typically several tenths to hundreds electron volt. As such the ions can have a strong impact on the film properties. In the case of magnetron sputtering, this will lead to inhomogenous film properties over the substrate facing the locally eroded target. Due to their high energy, the trajectory of negative ions can be easily predicted which has led to several strategies to avoid negative ion bombardment such as facing target sputtering and off-axis sputtering. This paper reviews several facets of the production, the measurements and the impact on the film properties of negative ions during reactive sputtering. Despite the many illustrative studies on the impact of negative oxygen ions, quantification is often lacking as the negative ion yield is only known for a few oxides. The compilation of several literature sources allows the discussed trends to be placed in a quantitative framework. [ABSTRACT FROM AUTHOR]

A facile and versatile methodology is developed for the synthesis of diverse gold nanostructured arrays employing an oxide secondary template combined with sputtering deposition. A bowl‐shaped tin oxide‐built array, with fine structure on its bowl edges, is first designed and prepared by solution‐dipping of an organic colloidal monolayer, drying, and heating treatment. This array is then used as a secondary template for a gold nanostructured array by sputtering deposition on it. By controlling the solution's concentration and drying rate to adjust the fine structure of the secondary template, various new gold nanostructured arrays with hexagonal arrangement are fabricated, including "graphene‐structured" gold nanoarray, non‐contact nanoparticle's ring array, closely contacted nanoring array, and bowl/nanoparticle binary composite nanoarray, achieving the structural diversity and morphological tunability of nanoarrays. Additionally, these gold nanostructured arrays can transition from hydrophilic to hydrophobic properties solely by adjusting their surface architecture. Importantly, the bowl‐shaped structural units within these gold nanoarrays demonstrate a marked capability for capturing target molecules that can only very weakly interact with plasmonic metals. This work offers an efficient route to achieve the structural diversity of nanoarrays, which is of significance in designing and fabricating foundational materials for the next generation of multifunctional nanodevices. [ABSTRACT FROM AUTHOR]

This study investigated the biochemical and microbiological properties of Cotton–Copper composite materials obtained using magnetron sputtering technology. Copper particles were precisely distributed on the fabric surface, ensuring free airflow without the need to create additional layers. The Cotton–Copper composite materials were subjected to physiochemical and biological investigations. The physiochemical analysis included the elemental analysis of composites (C, N, O, S, Cu) and analyses of their microscopic and surface properties (specific surface area and total pore volume). The biological investigations consisted of microbiological and biochemical–hematological tests, including evaluation of the activated partial thromboplastin time and prothrombin time. Experiments showed significant effectiveness of the antibacterial material against representative strains of fungi and bacterial species. We also demonstrated the ability of the cotton–copper material to interact directly with the plasmid DNA. [ABSTRACT FROM AUTHOR]

High power impulse magnetron sputtering (HiPIMS) discharges with a zirconium target are studied experimentally and by applying the ionization region model (IRM). The measured ionized flux fraction lies in the range between 25% and 59% and increases with increased peak discharge current density ranging from 0.5 to 2 A/cm 2 at a working gas pressure of 1 Pa. At the same time, the sputter rate-normalized deposition rate determined by the IRM decreases in accordance with the HiPIMS compromise. For a given discharge current and voltage waveform, using the measured ionized flux fraction to lock the model, the IRM provides the temporal variation of the various species and the average electron energy within the ionization region, as well as internal discharge parameters such as the ionization probability and the back-attraction probability of the sputtered species. The ionization probability is found to be in the range 73%–91%, and the back-attraction probability is in the range 67%–77%. Significant working gas rarefaction is observed in these discharges. The degree of working gas rarefaction is in the range 45%–85%, higher for low pressure and higher peak discharge current density. We find electron impact ionization to be the main contributor to working gas rarefaction, with over 80% contribution, while kick-out by zirconium atoms and argon atoms from the target has a smaller contribution. The dominating contribution of electron impact ionization to working gas rarefaction is very similar to other low sputter yield materials. [ABSTRACT FROM AUTHOR]

The deposition of a thin LixSny alloy layer by plasma vapor deposition (PVD) on the surface of a Li foil is reported. The formation of a Li-rich alloy is confirmed by the volume expansion (up to 380%) of the layer and by the disappearance of metallic Sn peaks in the X-ray diffractogram. The layer has a much higher hardness than bare Li and can withstand aggressive cycling at 1C. Post-mortem scanning electron microscope observations revealed that the alloy layer remains intact even after fast cycling for hundreds of cycles. A concept of double modification by adding a thin ceramic/polymer layer deposited by a doctor blade on top of the LixSny layer was also reported to be efficient to reach long-term stability for 500 cycles at C/3. Finally, a post-treatment after Sn deposition consisting of a plasma cleaning of the LixSny alloy layer led to a strong improvement in the cycling performance at 1C. The surface is smoother and less oxidized after this treatment. The combination of a Li-rich alloy interlayer, the increase in hardness at the electrolyte/Li interface, and the absence of dissolution of the layer during cycling at high C-rates are reasons for such an improvement in electrochemical performance. [ABSTRACT FROM AUTHOR]

The paper presents the study concerning the preparation and physio-chemical and biological properties of wool–copper (WO-Cu) materials obtained by the sputter deposition of copper onto the wool fibers. The WO-Cu material was subjected to physio-chemical and biological investigations. The physio-chemical investigations included the elemental analysis of materials (C, N, O, S, and Cu), their microscopic analysis, and surface properties analysis (specific surface area and total pore volume). The biological investigations consisted of the antimicrobial activity tests of the WO-Cu materials against colonies of Gram-positive (Staphylococcus aureus) bacteria, Gram-negative (Escherichia coli) bacteria, and fungal mold species (Chaetomium globosum). Biochemical–hematological tests included the evaluation of the activated partial thromboplastin time and pro-thrombin time. The tested wool–copper demonstrated the ability to interact with the DNA in a time-dependent manner. These interactions led to the DNA's breaking and degradation. The antimicrobial and antifungal activities of the WO-Cu materials suggest a potential application as an antibacterial/antifungal material. Wool–copper materials may be also used as customized materials where the blood coagulation process could be well controlled through the appropriate copper content. [ABSTRACT FROM AUTHOR]

We have fabricated smooth-surfaced amorphous In2O3:Sn (a-ITO) films at a high temperature of 550 °C, far above the typical crystallization threshold of 150 °C for ITO films. This achievement has been made possible by intentionally introducing N2 into the sputtering atmosphere, which maintains a low N atom incorporation of only a few atomic percent within the films. Positioned within ZONE-T of the Thornton diagram (higher-temperature region characterized by high film density), our method allows the preparation of films with superior film density about 6.96 g/cm3, substantially exceeding the density of 6.58 g/cm3 for conventional a-ITO films fabricated under ZONE-1 (low-temperature region) and approaching the bulk crystal density of In2O3 at 7.12 g/cm3. The films also feature a high carrier density of 5 × 1020 cm−3 and a remarkably low resistivity of 3.5 × 10−4 Ω cm, comparable to those of polycrystalline films. The analysis via vacuum-ultraviolet absorption spectroscopy on N and O atom densities in the plasma suggests that amorphization is primarily caused not by N atoms incorporated in the films but by those temporally adsorbed on the film surface, inhibiting crystal nucleation before eventually desorbing. Our findings will pave the way not only for broader applications of a-ITO films but also for the design of other amorphous materials at temperatures beyond their crystallization points. [ABSTRACT FROM AUTHOR]

Summary: PVD Coatings Enable Textile Wires and Sensors – Process control by adjusted energy ranges Plasma sputtering deposition is a Physical Vapor Deposition (PVD) method based on a weakly ionized gas, the plasma, that ablates atoms from a solid target material at vacuum conditions to deposit the sputtered atoms on a substrate. In this way, the plasma has two functions, i) the generation of high‐energy ions of several 100 eV accelerated to the target for sputtering, and ii) to support film growth by plasma‐surface interaction with particles bearing lower energies around ∼10 eV. For both processes, energy thresholds are present, which will be discussed in this article. Plasma sputtering deposition has wide spread industrial applications. As one example, the metallization of polymer fibers is demonstrated to obtain electrically conductive textile sensors and wires. [ABSTRACT FROM AUTHOR]

Abstract Interfacial bond formation during sputter deposition of metal‐oxide thin films onto polycarbonate (PC) is investigated by ab initio molecular dynamics simulations and X‐ray photoelectron spectroscopy (XPS) analysis of PC|X interfaces (X = Al2O3, TiO2, TiAlO2). Generally, the predicted bond formation is consistent with the experimental data. For all three interfaces, the majority of bonds identified by XPS are (C─O)─metal bonds, whereas C─metal bonds are the minority. Compared to the PC|Al2O3 interface, the PC|TiO2 and PC|TiAlO2 interfaces exhibit a reduction in the measured interfacial bond density by 75 and ∼65%, respectively. Multiplying the predicted bond strength with the corresponding experimentally determined interfacial bond density shows that Al2O3 exhibits the strongest interface with PC, while TiO2 and TiAlO2 exhibit ∼70 and ∼60% weaker interfaces, respectively. This can be understood by considering the complex interplay between the metal‐oxide composition, the bond strength, and the population of bonds formed across the interface.

Sputter-deposited thin films of pure chromium and of chromium with small amounts of nitrogen are characterized regarding their electrical resistivity and strain dependence, i.e., piezoresistivity. They show a temperature dependent piezoresistive effect with gauge factors ranging approximately from 10 to 20. Related to this effect, they exhibit signs of a paramagnetic–antiferromagnetic transition at temperatures of 420 K and higher. For characterization, resistivity is measured at different strain levels: in a bending setup with a fixed radius and in a four-point bending system with reference strain gauges. Several parameter series of the sputter deposition of pure Cr films show that the higher gauge factor is correlated to a higher temperature coefficient of resistivity (TCR). The addition of nitrogen extends the range of TCR toward negative values, with gauge factors still in the same range as pure Cr. A Cr–N strain gauge is characterized and shows a linear, low-hysteresis strain–resistivity effect as well as a relatively large transverse sensitivity. Resistivity and gauge factor of one Cr and one Cr–N sample are measured from room temperature up to 600 K. These films have a resistivity anomaly indicating an antiferromagnetic ordering temperature T N that is much higher than in bulk Cr. The gauge factor has a maximum near T N and falls to small values at higher temperatures. The results indicate that the piezoresistivity of Cr and Cr-rich films is coupled to their spin-density wave (SDW) antiferromagnetism. Since the SDW state is known to be tunable through alloying, internal stress, and crystallinity, it appears that piezoresistivity can be influenced by these parameters as well. [ABSTRACT FROM AUTHOR]

This paper reports a novel additive manufacturing technique for MEMS devices using newly developed APSLD (atmospheric pressure sputtering layer deposition) technology. It uses a microplasma at atmospheric pressure to deposit microstructures with defined properties, such as conducting or isolating directly at different surfaces additively without complex and time‐consuming manufacturing routes like planar technology. Feasibility tests have been successfully done to deposit metal lines, isolating and metal oxide layers on 3D surfaces to manufacture high stable MEMS sensor system for harsh environments. This is a promising technology in the field of MEMS manufacturing, as it can simplify the manufacturing process and reduce the cost. The ability to deposit different materials can expand the design possibilities for MEMS devices. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

ZrC dispersion-strengthened W exhibits high strength/ductility, low ductile-to-brittle transition temperature, and excellent thermal shock resistance, making it a promising candidate plasma-facing material for future fusion devices. In this study, surface modification of 0.5 wt.% ZrC dispersion-strengthened W (WZrC) under low energy and high fluence He plasma irradiation at high temperature was presented. Under the energy of 90 eV and fluence ranging from 6 × 1024 He·m−2–2 × 1026 He·m−2 He irradiation at 920 °C, a typical fuzz nanostructure appeared on the W matrix of WZrC. The thickness of fuzz layer is proportional to the square root of He irradiation fluence. The fuzz showed comparable thickness and structural features to pure W, indicating limited effects of the particle's addition on resistance to high fluence He irradiation at high temperatures. Under continuous He injection, the fuzz would grow extending onto the particle area, making the particle obscured. Besides, the erosion behavior of particles under He plasma irradiation has been investigated, which is thought to be dominated by a sputtering process. Under the He influence of 6 × 1024 He·m−2, only nanopores were observed in the surface region. With fluence increasing to 5 × 1025 He·m−2, the surface became relatively uneven with larger holes. W aggregated in spots and distributed on the surface of the particle, which might be the result of subthreshold sputtering and deposition. When fluence further increased to 2 × 1026 He·m−2, the particles were eroded completely and covered by the extended fuzz, forming cavities. In addition, distinctive layered nanotendrils were observed above the cavities, which were characterized to consist of inner W-riched skeletons and outer Zr-riched layers. It indicates that the layered nanotendrils should be the result of fuzz extension combined with particle sputtering/deposition. [ABSTRACT FROM AUTHOR]

This study reports the pulsed sputtering deposition (PSD) epitaxial growth of In–Mg‐codoped GaN with a high hole concentration of 6.2 × 1018 cm−3 and its hole conduction mechanism. X‐ray diffraction analysis shows that In–Mg‐codoped GaN coherently grows on a GaN substrate without structural degradation and In concentration is 1.3%. Temperature‐dependent conductivity is explained by the combination of the band and nearest‐neighbor hopping conduction models. Curve fitting in the band conduction region is used to estimate the Mg activation energy, which is as low as 89 meV. This is responsible for the high hole concentration of 6.2 × 1018 cm−3. These results indicate that In–Mg codoping using low‐temperature PSD is a promising technique for the preparation of GaN with a high hole concentration without structural degradation. [ABSTRACT FROM AUTHOR]

Rechargeable Li–S batteries (LSBs) are emerging as an important alternative to lithium‐ion batteries (LIBs), owing to their high energy densities and low cost; yet sluggish redox kinetics of LiPSs results in inferior cycle life. Herein, we prepared multifunctional self‐supporting hyphae carbon nanobelt (HCNB) as hosts by carbonization of hyphae balls of Rhizopus, which could increase the S loading of the cathode without sacrificing reaction kinetics. Trace platinum (Pt) nanoparticles were introduced into HCNBs (PtHCNBs) by ion‐beam sputtering deposition. Based on the X‐ray photoelectron spectroscopy analyses, the introduced trace Pt regulated the local electronic states of heteroatoms in HCNBs. Electrochemical kinetics investigation combined with operando Raman measurements revealed the accelerated reaction mechanics of sulfur species. Benefiting from the synergistic catalytic effect and the unique structures, the as‐prepared PtHCNB/MWNCT/S cathodes delivered a stable capacity retention of 77% for 400 cycles at 0.5 C with a sulfur loading of 4.6 mg cm−2. More importantly, remarkable cycling performance was achieved with an high areal S loading of 7.6 mg cm−2. This finding offers a new strategy to prolong the cycle life of LSBs. [ABSTRACT FROM AUTHOR]

We introduce a Bayesian optimization approach to guide the sputter deposition of molybdenum thin films, aiming to achieve desired residual stress and sheet resistance while minimizing susceptibility to stochastic fluctuations during deposition. Thin films are pivotal in numerous technologies, including semiconductors and optical devices, where their properties are critical. Sputter deposition parameters, such as deposition power, vacuum chamber pressure, and working distance, influence physical properties like residual stress and resistance. Excessive stress and high resistance can impair device performance, necessitating the selection of optimal process parameters. Furthermore, these parameters should ensure the consistency and reliability of thin film properties, assisting in the reproducibility of the devices. However, exploring the multidimensional design space for process optimization is expensive. Bayesian optimization is ideal for optimizing inputs/parameters of general black-box functions without reliance on gradient information. We utilize Bayesian optimization to optimize deposition power and pressure using a custom-built objective function incorporating observed stress and resistance data. Additionally, we integrate prior knowledge of stress variation with pressure into the objective function to prioritize films least affected by stochastic variations. Our findings demonstrate that Bayesian optimization effectively explores the design space and identifies optimal parameter combinations meeting desired stress and resistance specifications. [ABSTRACT FROM AUTHOR]

β -Ga2O3 is actively touted as the next ultrawide bandgap material for power electronics. To fully utilize its high intrinsic critical electric field, development of high-quality robust large-barrier height junctions is essential. To this end, various high-work function metals, metal oxides, and hole-conducting oxides have been deposited on Ga2O3, primarily formed by sputter deposition. Unfortunately, reports to date indicate that measured barrier heights often deviate from the Schottky–Mott model as well as x-ray photoelectron spectroscopy (XPS) extractions of conduction band offsets, suggesting significant densities of electrically active defects at these junctions. We report Schottky diodes made from noble metal oxides, IrO2 and RuO2, deposited by ozone molecular beam epitaxy (ozone MBE) with barrier heights near 1.8 eV. These barriers show close agreement across extraction methods and robust to high surface electric fields upward of 6 MV/cm and 60 A/cm2 reverse current without degradation. [ABSTRACT FROM AUTHOR]

Recently, there has been increasing interest in the use of hot targets to enhance the sputter deposition of materials. However, the actual temperature of the target surface is normally not known. In this work, we directly measured the radial distribution of the surface temperature of a MAK 2 in. Ti water-cooled target using a type K thermocouple during the operation of the sputtering system. Principally, the measurements were made as a function of applied DC power and argon gas pressure. Given the importance of chemical reactions between the gas and the target during reactive sputtering, we have also measured the target temperature as a function of the nitrogen concentration in an argon-nitrogen gas mixture. A few of the reactively sputtered samples were analyzed by x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Wurtzite-type aluminum nitride (AlN) thin films exhibiting high thermal conductivity, large grain size, and low surface roughness are desired for both bulk acoustic wave and surface acoustic wave resonators. In this work, we use ammonia (NH3) assisted reactive sputter deposition of AlN to significantly improve these properties. The study shows a systematic change in the structural, thermal, and morphological properties of AlN grown in nitrogen (N2) and N2 + NH3 atmosphere. The study demonstrates that NH3 assisted AlN sputtering facilitates 2D growth. In addition, the study presents a growth model relating the 2D growth to improve the mobility of aluminum (Al) and nitrogen (N) ad-atoms in NH3 atmosphere. Consequently, the thermal conductivity and roughness improve by ≈ 76%, and ≈ 35%, while the grain size increases by ≈ 78%. [ABSTRACT FROM AUTHOR]

The influence of the pulse frequency and duty cycle on the elemental composition, microstructure, and mechanical properties of Ti–Al–Ta–N coatings deposited by middle-frequency magnetron sputtering is studied. An increase in the pulse frequency and duty cycle is found to lead to a decrease in the deposition rate and sputtering yield as well as to variations of the coating composition. The coatings deposited at a pulse frequency of 50 kHz have a denser mixed microstructure, while those obtained at 100 kHz are characterized by pronounced columnar morphology. The hardness of the coatings slightly decreases with increasing duty cycle. Thus, the coatings with dense microstructure and maximum hardness are obtained at a pulse frequency of 50 kHz and a duty cycle of 60%. [ABSTRACT FROM AUTHOR]

This work explores the use of air as a reactive gas in the sputtering deposition of N-doped TiO 2 -based bilayer, gradient, and multilayer thin films for photoelectrochemical evaluations. By merely adjusting the air/Ar flow ratio, crystalline phases, nitrogen doping contents, electrical properties, optical bandgaps, and valence band maximum (VBM) positions of N–TiO 2 films were tailored. The N–TiO 2 /TiN(O) bilayer on the glass substrates exhibited a peak photocurrent density of 776 μA cm−2 at an air/Ar ratio of 1.60, which may be due to suitable bandgap and carrier mobility of the TiO 2 overlayer as the bandgap was affected by the nitrogen content and rutile fraction in the TiO 2 overlayer. To further improve the performance of N–TiO 2 , stepwise and sequential gradient structures with gradient bandgaps and nitrogen contents were produced, which could reach photocurrent densities of 805 ± 4 and 837 ± 3 μA cm−2, respectively. The gradient structures lead to enhanced light absorption efficiency and reduce carrier recombination. The N–TiO 2 /TiN(O) multilayer structures were also designed and revealed the highest photocurrent density of 865 ± 7 μA cm−2. Such evident enhancement is mainly due to the thin conductive while translucent TiN(O) layers between the photoelectrochemical-active N–TiO 2 layers provide multiple low-impedance channels in enhancing carrier transport. [Display omitted] • N–TiO 2 -based bilayer, gradient, and multilayer films were made by air sputtering. • Enhancements of photocurrents were achieved via gradient and multilayer designs. • N–TiO 2 gradient films with N-gradients were produced by varying air/Ar ratios. • Multiple thin translucent TiN(O) films provide low-impedance paths in the multilayer. • Obtained highest photocurrent density was 865 ± 7 μA cm−2. [ABSTRACT FROM AUTHOR]

The deposition of gold-colored titanium nitride films without applying substrate heating is of significant interest due to the increasing demand for decorative coatings on temperature-sensitive three-dimensional substrates. Here, the energetic impact of Nb1+ ions during the deposition of TiN was achieved within a bipolar high-power impulse magnetron sputtering discharge operating on a Nb target. A separate titanium target was operated with direct current magnetron sputtering in the same reactive argon–nitrogen mixture. This process aimed to achieve a dense titanium nitride with the assistance of the niobium ion bombardment. The niobium controlled the phase formation and structure of the resulting Nb-containing TiN coating without needing external heating. The niobium ion bombardment during deposition increases the density of the titanium nitride coatings, promoting the formation of the cubic phase favored for its gold color and excellent mechanical and tribological properties, including HF1-level adhesion. Energy-selective mass spectrometer investigations revealed an increase in the flux and the energy of titanium ions due to momentum transfer from niobium ions to titanium neutrals in the plasma generated between the targets and the substrate. The approach introduced here paves the way for the formation of the cubic phase of Nb-doped TiN films without external heating, producing coatings with combined decorative and protective properties. [ABSTRACT FROM AUTHOR]

Professor Joseph "Joe" Greene taught me a great deal about research, leadership, and how to succeed. He was a mentor and a tireless advocate for me over the course of my career. This article summarizes some of the work that my research group carried out, inspired by Prof. Greene but not in direct collaboration with him. Three examples of these efforts are provided, epitaxial growth of Cu(In,Ga)Se2 (CIGS) on GaAs by sputter deposition, synthesis of Cu-Mo metastable alloys by sputter deposition, and recrystallization of CIGS deposited at high rates by treatment with metal halides. These works were carried out with many collaborators who are acknowledged in the description of the research carried out by them and in the references where full details can be found. [ABSTRACT FROM AUTHOR]

Compressive stresses in sputter deposited thin films are generally assumed to be caused by forward sputtered (peened) built-in particles and entrapped working gas atoms. While the former are assumed to be predominant, the effect of the latter on interaction dynamics and thin film properties is scarcely clarified (concurrent or causative). The overlay of the ion bombardment induced processes renders an isolation of their contribution impracticable. This issue is addressed by two molecular dynamics case studies considering the sputter deposition of Al thin films in Ar working gas. First, Ar atoms are fully retained. Second, they are artificially neglected, as implanted Ar atoms are assumed to outgas anyhow and not alter the ongoing dynamics significantly. Both case studies share common particle dose impinging Al(001) surfaces. Ion energies from 3 to 300 eV and Al / Ar + flux ratios from 0 to 1 are considered. The surface interactions are simulated by hybrid reactive molecular dynamics/force-biased Monte Carlo simulations and characterized in terms of mass density, Ar concentration, biaxial stress, shear stress, ring statistical connectivity profile, Ar gas porosity, Al vacancy density, and root-mean-squared roughness. Implanted Ar atoms are found to form subnanometer sized eventually outgassing clusters for ion energies exceeding 100 eV. They fundamentally govern a variety of surface processes (e.g., forward sputtering/peening) and surface properties (e.g., compressive stresses) in the considered operating regime. [ABSTRACT FROM AUTHOR]