Search

The development of two-dimensional (2D) materials has gained significant attention due to their unique properties and potential applications in advanced electronics. This study investigates the fabrication and characterization of Fe-doped SnSe semiconductors using an optimized chemical vapor deposition (CVD) method. Fe doping was achieved by dissolving FeCl3 in deionized water, applying it to SnSe powder, and conducting vacuum drying followed by high-temperature CVD at 820 °C. Structural and morphological properties were characterized using optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Results revealed differently shaped flakes, including rectangles, discs and wires, influenced by Fe content. Micro-Raman spectroscopy showed significant vibrational mode shifts, indicating structural changes. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Sn-Se and Fe-Se bonds. Electrical characterization of the memristive devices showed stable switching between high- and low-resistance states, with a threshold voltage of 1.6 V. These findings suggest that Fe-doped SnSe is a promising material for non-volatile memory and neuromorphic computing applications. [ABSTRACT FROM AUTHOR]

The development of kesterite (Cu2ZnSn(S,Se)4, CZTSSe) thin films for photovoltaic applications is highly necessary, given their composition of Earth-abundant, environmentally friendly elements and their compatibility with established photovoltaic technologies. This study presents a novel synthesis approach for CZTSSe films with varied S/(S+Se) ratios, ranging from 0.83 to 0.44, by a two-step magnetron sputtering deposition/annealing process. The first step consists in an initial deposition of stacked Mo/SnS2/Cu layers, which, upon thermal treatment in a sulfur atmosphere, were transformed into Cu2SnS3 (CTS) films. In the second step, further deposition of ZnSe and subsequent annealing in a tin and selenium atmosphere resulted in the formation of a CZTSSe phase. These processes were optimized to fabricate high-quality and single-phase CZTSSe films, thereby mitigating the formation of secondary phases. Characterization techniques, including scanning electron microscopy, demonstrated a clear correlation between decreased S/(S+Se) ratios and enhanced film densification and grain size. Moreover, grazing incidence X-ray diffraction and Raman spectroscopy confirmed a compositional and structural transition from close to CZTS to nearly a CZTSe phase as the S/(S+Se) ratios decreased. This study advances kesterite-based solar cell technology by enhancing the structural properties and crystallinity of the absorber layer, necessary for improving photovoltaic performance. [ABSTRACT FROM AUTHOR]

Recently, a smart strategy for two-dimensional (2D) materials synthesis has emerged, namely space-confined chemical vapor deposition (CVD). Its extreme case is the microreactor method, in which the growth substrate is face-to-face stacked on the source substrate. In order to grow 2D transition metal dichalcogenides by this method, transition metal oxides, dispersed in very small amounts on the source substrate, are used as source materials in most of the published reports. In this paper, a colloidal dispersion of MoS2 in saline solution is used and MoS2 nanosheets with various shapes, sizes (between 5 and 60 μm) and thicknesses (2–4 layers) have been synthesized. Small MoS2 flakes (regular or defective) are present on the surface of the nanosheets. Catalytic sites, undercoordinated atoms located at the edges of MoS2 flakes and nanosheets, are produced in a high number by a layer-plus-island (Stranski–Krastanov) growth mechanism. Several double-resonance Raman bands (at 147, 177, 187, 225, 247, 375 cm−1) are assignable to single phonon processes in which the excited electron is elastically scattered on a defect. The narrow 247 cm−1 peak is identified as a topological defect-activated peak. These findings highlight the potential of defect engineering in material property optimization, particularly for solar water splitting applications. [ABSTRACT FROM AUTHOR]

Considering the increasing need for sustainable and economical energy storage solutions, the integration of layered materials such as MoS2 into these systems represents an important step toward enhancing energy sustainability and efficiency. Exploring environmentally responsible fabrication techniques, this study assesses wrinkled MoS2 thin films synthesized from distinct Mo and MoS2 targets, followed by sulfurization conducted in a graphite box. We utilized magnetron sputtering to deposit precursor Mo and MoS2 films on Si substrates, achieving thicknesses below 20 nm. This novel approach decreases sulfur by up to tenfold during sulfurization due to the confined space technique, contributing also to avoiding the formation of toxic gases such as SO2 or the necessity of using H2S, aligning with sustainable materials development. Thinner MoS2 layers were obtained post-sulfurization from the MoS2 precursors, as shown by X-ray reflectometry. Raman spectroscopy and grazing X-ray diffraction analyses confirmed the amorphous nature of the as-deposited films. Post-sulfurization, both types of films exhibited crystalline hexagonal MoS2 phases, with the sulfurized Mo showing a polycrystalline nature with a (100) orientation and sulfurized MoS2 displaying a (00L) preferred orientation. The X-ray photoelectron spectroscopy results supported a Mo:S ratio of 1:2 on the surface of the films obtained using the MoS2 precursor films, confirming the stoichiometry obtained by means of energy dispersive X-ray spectroscopy. Scanning electron microscopy and atomic force microscopy images revealed micrometer-sized clusters potentially formed during rapid cooling post-sulfurization, with an increased average roughness. These results open the way for the further exploration of wrinkled MoS2 thin films in advanced energy storage technologies. [ABSTRACT FROM AUTHOR]

Kesterite-based copper zinc tin sulfide (CZTS) and copper zinc tin selenide (CZTSe) thin films have attracted considerable attention as promising materials for sustainable and cost-effective thin-film solar cells. However, the successful integration of these materials into photovoltaic devices is hindered by the coexistence of secondary phases, which can significantly affect device performance and stability. This review article provides a comprehensive overview of recent progress and challenges in controlling secondary phases in kesterite CZTS and CZTSe thin films. Drawing from relevant studies, we discuss state-of-the-art strategies and techniques employed to mitigate the formation of secondary phases. These include a range of deposition methods, such as electrodeposition, sol-gel, spray pyrolysis, evaporation, pulsed laser deposition, and sputtering, each presenting distinct benefits in enhancing phase purity. This study highlights the importance of employing various characterization techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, for the precise identification of secondary phases in CZTS and CZTSe thin films. Furthermore, the review discusses innovative strategies and techniques aimed at mitigating the occurrence of secondary phases, including process optimization, compositional tuning, and post-deposition treatments. These approaches offer promising avenues for enhancing the purity and performance of kesterite-based thin-film solar cells. Challenges and open questions in this field are addressed, and potential future research directions are proposed. By comprehensively analyzing recent advancements, this review contributes to a deeper understanding of secondary phase-related issues in kesterite CZT(S/Se) thin films, paving the way for enhanced performance and commercial viability of thin-film solar cell technologies. [ABSTRACT FROM AUTHOR]

In the quest for advanced materials suitable for next-generation electronic and optoelectronic applications, tungsten disulfide (WS2) ultrathin films have emerged as promising candidates due to their unique properties. However, obtaining WS2 directly on the desired substrate, eliminating the need for transfer, which produces additional defects, poses many challenges. This paper aims to explore the synthesis of WS2 ultrathin films via physical vapor deposition (PVD) followed by sulfurization in a confined space, addressing the challenge of film formation for practical applications. Precursor layers of tungsten and WS2 were deposited by RF magnetron sputtering. Subsequent sulfurization treatments were conducted in a small, closed, graphite box to produce WS2 films. The physical and chemical properties of these precursor and sulfurized layers were thoroughly characterized using techniques such as X-ray reflectometry (XRR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings reveal notable distinctions in film thickness, structural orientation, and chemical composition, attributable to the different precursor used. Particularly, the sulfurized layers from the tungsten precursor exhibited a preferred orientation of WS2 crystallites with their (00L) planes parallel to the substrate surface, along with a deviation from parallelism in a small angular range. This study highlights the necessity of precise control over deposition and sulfurization parameters to tailor the properties of WS2 films for specific technological applications. [ABSTRACT FROM AUTHOR]

This study investigates the morphological changes induced by femtosecond (fs) laser pulses in arsenic trisulfide (As2S3) thin films and gold–arsenic trisulfide (Au\As2S3) heterostructures, grown by pulsed laser deposition (PLD). By means of a direct laser writing experimental setup, the films were systematically irradiated at various laser power and irradiation times to observe their effects on surface modifications. AFM was employed for morphological and topological characterization. Our results reveal a clear transition threshold between photoexpansion and photoevaporation phenomena under different femtosecond laser power regimes, occurring between 1 and 1.5 mW, irrespective of exposure time. Notably, the presence of a gold layer in the heterostructure minimally influenced this threshold. A maximum photoexpansion of 5.2% was obtained in As2S3 films, while the Au\As2S3 heterostructure exhibited a peak photoexpansion of 0.8%. The study also includes a comparative analysis of continuous-wave (cw) laser irradiation, confirming the efficiency of fs laser pulses in inducing photoexpansion effects. [ABSTRACT FROM AUTHOR]

Cu2ZnSnSe4 thin films have been synthesized by employing two magnetron-sputtering depositions, interlaced with two sequential post-deposition heat treatments in low vacuum, Sn+Se and Se–rich atmospheres at 550 °C. By employing successive structural analysis methods, namely Grazing Incidence X–Ray Diffraction (GIXRD) and Raman Spectroscopy, secondary phases such as ZnSe coexisting with the main kesterite phase have been identified. SEM peered into the surface morphology of the samples, detecting structural defects and grain profiles, while EDS experiments showed off–stoichiometric elemental composition. The optical bandgaps in our samples were calculated by a widely used extrapolation method from recorded transmission spectra, holding values from 1.42 to 2.01 eV. Understanding the processes behind the appearance of secondary phases and occurring structural defects accompanied by finding ways to mitigate their impact on the solar cells' properties is the prime goal of the research beforehand. [ABSTRACT FROM AUTHOR]

The consumer market requests infrared (IR) optical components, made of relatively abundant and environmentally friendly materials, to be integrated or attached to smartphones. For this purpose, three new chalcogenides samples, namely Ge23.3Zn30.0Se46.7 (d_GZSe-1), Ge26.7Zn20.0Se53.3 (d_GZSe-2) and Ba4.0Ge12.0Zn17.0Se59.0I8.0 (d_GZSe-3) were obtained by mechanical alloying and processed by spark plasma sintering into dense bulk disks. Obtaining a completely amorphous and homogeneous material proved to be difficult. d_GZSe-2 and d_GZSe-3 are glass-ceramics with the amount of the amorphous phase being 19.7 and 51.4 wt. %, while d_GZSe-1 is fully polycrystalline. Doping with barium and iodine preserves the amorphous phase formed by milling and lowers the sintering temperature from 350 °C to 200 °C. The main crystalline phase in all of the prepared samples is cubic ZnSe or cubic Zn0.5Ge0.25Se, while in d_GZSe-3 the amorphous phase contains GeSe4 clusters. The color of the first two sintered samples is black (the band gap values are 0.42 and 0.79 eV), while d_GZSe-3 is red (Eg is 1.37 eV) and is transparent in IR domain. These results are promising for future research in IR materials and thin films. [ABSTRACT FROM AUTHOR]

Phase‐change memories have reached an advanced degree of maturity, although, to be able to meet the increasing storage demand, multilevel capability is needed. A GeTe memristor is obtained in an amorphous state and it is subjected to a specific thermal treatment which initiates the transition toward the crystalline state. It is found that this crystalline state initialization process is highly beneficial for subsequently obtaining a large number of intermediate resistive states between the high and low resistive states. Multiple resistance levels are achieved by operating the devices in both DC sweeps and rectangular pulse modes in the low‐voltage subthreshold regime. The conduction is modeled using a space charge limited conduction model, showing three distinct conduction regions in the high resistive state which merge toward a single conduction region as the low resistive state is approached. The obtained memristors can be used as multilevel nonvolatile memories or as synapses in neuromorphic computing. [ABSTRACT FROM AUTHOR]

Almost six decades ago, in Romania a small group of physicists begun to study chalcogenide compositions, motivated primarily by the desire to understand the phase‐change phenomenon in these materials, discovered recently, at that time, by Stanford R. Ovshinsky. It took not too long for them to realize the challenges these materials set to the research. With newcomers to the field, the research was broadened. In some cases just for basic research, to model, and to understand the chalcogenide materials, whereas in other cases, the applicative potential was revealed and used. Herein, the evolution of the field of these somewhat exotic materials is followed, listing the main contributions done in Romania, both in basic and applied research. [ABSTRACT FROM AUTHOR]

The thermal stress effect on the structure of phase change memory materials, namely single films and double stacked films of GeTe and SnSe, is evaluated. The crystallization temperatures of GeTe and SnSe single films are 138 °C and 292 °C, respectively. The films are amorphous before annealing and crystallize in rhombohedral and orthorhombic structures afterwards. Ge is tetrahedrally bonded and Se is bivalent after deposition. Both Ge and Se have an octahedral configuration after annealing. The double stacked structure is studied in the as‐deposited state and after annealing at temperatures of 100, 210, and 350 °C. Pulsed laser deposition produces the crystallization of both as‐deposited layers when stacked, mostly of SnSe, but also some crystalline GeTe is present. GeTe fully crystallizes after annealing at 210 °C, in the face‐centred cubic structure. Annealing at 350 °C leads to the evaporation of a significant quantity of Se and to the formation of a cubic Ge0.75Sn0.25Te solid solution. Ge has an octahedral coordination, while Se is tetrahedrally bonded as a result of a combination of bivalent amorphous Se and octahedral Se from crystalline SnSe. The study shows that diffusion between layers at high annealing temperatures might suppress the memory property and determines the formation of irreversible solid solutions. [ABSTRACT FROM AUTHOR]

The compositions in the ternary chalcogenide systems from the demarcation region between the glass-formation domain (GFD) and the partially or fully crystalline formation domain seem to exhibit outstanding properties. We have shown in this paper that the compositions with the best memory-switching properties are situated at the border of the GFD in many systems. One can use this correlation to find new phase-change materials with better switching properties or to discover GFDs that were not observed yet. [ABSTRACT FROM AUTHOR]

Monitoring the silver photodiffusion in thin amorphous As2S3 film is addressed with a new experimental setup. A possible photo‐diffusion mechanism of silver into the a‐As2S3 thin film under green laser diode light (λ = 532 nm) irradiation is proposed. The proposed mechanism is based on a gradual filling of the structural voids existing in the network of the thin chalcogenide layer. This mechanism is supported by XRD measurements, optical absorption, and modeling data. [ABSTRACT FROM AUTHOR]

A new description of the switching phenomenon is given. The switching is regarded as due to the formation and breaking of the links between the dendrites of crystalline nuclei in bulk materials, as a consequence of the energy pumped by an electrical field. This mechanism explains the very short switching time (<20 ns), the possibility to get smart memories based on multisteps of resistivity and the high number of cycles supported by the cell (1016). A cellular automaton mechanism was created on the basis of this model for switching. Multistage memory in chalcogenide materials has also been explained by this mechanism. [ABSTRACT FROM AUTHOR]

Nanoscale thermometers with high sensitivity are needed in domains which study quantum and classical effects at cryogenic temperatures. Here, we present a micrometer sized and nanometer thick chromium selenide cryogenic temperature sensor capable of measuring a large domain of cryogenic temperatures down to tenths of K. Hexagonal Cr-Se flakes were obtained by a simple physical vapor transport method and investigated using scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy measurements. The flakes were transferred onto Au contacts using a dry transfer method and resistivity measurements were performed in a temperature range from 7 K to 300 K. The collected data have been fitted by exponential functions. The excellent fit quality allowed for the further extrapolation of resistivity values down to tenths of K. It has been shown that the logarithmic sensitivity of the sensor computed over a large domain of cryogenic temperature is higher than the sensitivity of thermometers commonly used in industry and research. This study opens the way to produce Cr-Se sensors for classical and quantum cryogenic measurements. [ABSTRACT FROM AUTHOR]

Cu2ZnSnS4 (CZTS) is a complex quaternary material, and obtaining a single-phase CZTS with no secondary phases is known to be challenging and dependent on the production technique. This work involves the synthesis and characterization of CZTS absorber layers for solar cells. Thin films were deposited on Si and glass substrates by a combined magnetron sputtering (MS) and pulsed laser deposition (PLD) hybrid system, followed by annealing without and with sulfur powder at 500 °C under argon (Ar) flow. Three different Cu2S, SnS2, and ZnS targets were used each time, employing a different target for PLD and the two others for MS. The effect of the different target arrangements and the role of annealing and/or sulfurization treatment were investigated. The characterization of the absorber films was performed by grazing incidence X-ray diffraction (GIXRD), X-ray reflectometry (XRR), Raman spectroscopy, scanning electron microscopy, and regular transmission spectroscopy. The film with ZnS deposited by PLD and SnS2 and Cu2S by MS was found to be the best for obtaining a single CZTS phase, with uniform surface morphology, a nearly stoichiometric composition, and an optimal band gap of 1.40 eV. These results show that a new method that combines the advantages of both MS and PLD techniques was successfully used to obtain single-phase Cu2ZnSnS4 films for solar cell applications. [ABSTRACT FROM AUTHOR]

ZnS is a wide band gap material which was proposed as a possible candidate to replace CdS as a buffer layer in solar cells. However, the structural and optical properties are influenced by the deposition method. ZnS thin films were prepared using magnetron sputtering (MS), pulsed laser deposition (PLD), and a combined deposition technique that uses the same bulk target for sputtering and PLD at the same time, named MSPLD. The compositional, structural, and optical properties of the as-deposited and annealed films were inferred from Rutherford backscattering spectrometry, X-ray diffraction, X-ray reflectometry, Raman spectroscopy, and spectroscopic ellipsometry. PLD leads to the best stoichiometric transfer from target to substrate, MS makes fully amorphous films, whereas MSPLD facilitates obtaining the densest films. The study reveals that the band gap is only slightly influenced by the deposition method, or by annealing, which is encouraging for photovoltaic applications. However, sulphur vacancies contribute to lowering the bandgap and therefore should be controlled. Moreover, the results add valuable information towards the understanding of ZnS polymorphism. The combined MSPLD method offers several advantages such as an increased deposition rate and the possibility to tune the optical properties of the obtained thin films. [ABSTRACT FROM AUTHOR]

Ge2Sb2Te5 (GST-225) is a chalcogenide material with applications in nonvolatile memories. However, chalcogenide material properties are dependent on the deposition technique. GST-225 thin films were prepared using three deposition methods: magnetron sputtering (MS), pulsed laser deposition (PLD) and a deposition technique that combines MS and PLD, namely MSPLD. In the MSPLD technique, the same bulk target is used for sputtering but also for PLD at the same time. The structural and optical properties of the as-deposited and annealed thin films were characterized by Rutherford backscattering spectrometry, X-ray reflectometry, X-ray diffraction, Raman spectroscopy and spectroscopic ellipsometry. MS has the advantage of easily leading to fully amorphous films and to a single crystalline phase after annealing. MS also produces the highest optical contrast between the as-deposited and annealed films. PLD leads to the best stoichiometric transfer, whereas the annealed MSPLD films have the highest mass density. All the as-deposited films obtained with the three methods have a similar optical bandgap of approximately 0.7 eV, which decreases after annealing, mostly in the case of the MS sample. This study reveals that the properties of GST-225 are significantly influenced by the deposition technique, and the proper method should be selected when targeting a specific application. In particular, for electrical and optical phase change memories, MS is the best suited deposition method. [ABSTRACT FROM AUTHOR]

The topological transition from order to disorder in crystalline silicon was investigated by a computer simulation procedure. The gradually introduction of topological Wooten–Winer–Weaire defect states makes the crystal change in a more and more disordered assembly of atoms. The characterization of deformation energy around a single defect state is analyzed. The topological transition from graphene structure to an amorphous carbon layer, by introduction of a high number of Stone–Wales defect‐type states was evidenced. The comparison of the disordered structure in tetrahedrally bonded semiconductors (silicon) and a two‐dimensional network based on graphene structure was made. [ABSTRACT FROM AUTHOR]

Cu2ZnSnS4 (CZTS) is an economically and environmentally friendly alternative to other toxic and expensive materials used for photovoltaics, however, the variation in the composition during synthesis is often followed by the occurrence of the secondary binary and ternary crystalline phases. These phases produce changes in the optical absorption edge important in cell efficiency. We explore here the secondary phases that emerge in a combinatorial Cu2S–ZnS–SnS2 thin films library. Thin films with a composition gradient were prepared by simultaneous magnetron sputtering from three binary chalcogenide targets (Cu2S, SnS2 and ZnS). Then, the samples were crystallized by sulfurization annealing at 450 °C under argon flow. Their composition was measured by energy dispersive X-ray spectroscopy (EDX), whereas the structural and optical properties were investigated by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and optical transmission measurements. As already known, we found that annealing in a sulfur environment is beneficial, increasing the crystallinity of the samples. Raman spectroscopy revealed the presence of CZTS in all the samples from the library. Secondary crystalline phases such as SnS2, ZnS and Cu–S are also formed in the samples depending on their proximity to the binary chalcogenide targets. The formation of ZnS or Cu–S strongly correlates with the Zn/Sn and Cu/Zn ratio of the total sample composition. The presence of these phases produces a variation in the bandgap between 1.41 eV and 1.68 eV. This study reveals that as we go further away from CZTS in the composition space, in the quasi-ternary Cu2S–ZnS–SnS2 diagram, secondary crystalline phases arise and increase in number, whereas the bandgap takes values outside the optimum range for photovoltaic applications. [ABSTRACT FROM AUTHOR]

Reduced activation ferritic and martensitic steel like EUROFER (9Cr-1W) are considered as potential structural materials for the first wall of the future next-generation DEMOnstration Power Station (DEMO) fusion reactor and as a reference material for the International Thermonuclear Experimental Reactor (ITER) test blanket module. The primary motivation of this work is to study the re-deposition of the main constituent materials of EUROFER, namely tungsten (W), iron (Fe), and chromium (Cr), in a DEMO type reactor by producing and analyzing complex WxCryFe1−x−y layers. The composite layers were produced in laboratory using the thermionic vacuum arc (TVA) method, and the morphology, crystalline structure, elemental composition, and mechanical properties were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-X-ray fluorescence (micro-XRF), and glow discharge optical emission spectrometry (GDOES), as well as nanoindentation and tribology measurements. The results show that the layer morphology is textured and is highly dependent on sample positioning during the deposition process. The formation of polycrystalline WxCryFe1−x−y was observed for all samples with the exception of the sample positioned closer to Fe anode during deposition. The crystalline grain size dimension varied between 10 and 20 nm. The composition and thickness of the layers were strongly influenced by the in-situ coating position, and the elemental depth profiles show a non-uniform distribution of Fe and Cr in the layers. The highest hardness was measured for the sample positioned near the Cr anode, 6.84 GPa, and the lowest was 4.84 GPa, measured for the sample positioned near the W anode. The tribology measurements showed an abrasive sliding wear behavior for most of the samples with a reduction of the friction coefficient with the increase of the normal load. [ABSTRACT FROM AUTHOR]

Abstract Bipolar Pulse High Power Impulse Magnetron Sputtering (BP-HiPIMS) was investigated and used in this work to control the ion bombardment process of growing thin films and to improve their structure and properties. Energy-resolving mass spectroscopy was used to investigate the effect of reverse target voltage on the ion energies and fluxes during BP-HiPIMS of a high-purity copper target, in argon gas. It was found that the reverse target voltage provides a wide range of ion energies and fluxes incident to the growing film, which, in turn, produce a wide variety of effects during the deposition process, improving the adhesion strength and influencing both surface and bulk properties. Fast ICCD imaging was used to investigate both HiPIMS and BP-HiPIMS plasma dynamics. The temporal and spatial distributions of plasma potential measurements were performed in order to explain the mechanisms for accelerating the ions. The topological, structural and mechanical properties of the deposited coatings were investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), thermal desorption spectroscopy (TDS), scanning electron microscopy (SEM), nanoindentation and scratch tests. The obtained results indicate an energy-enhanced deposition process during BP-HiPIMS, the deposited films being characterized by smooth surfaces, dense microstructure, small inert gas inclusions, high elastic strain to failure, scratch resistance and good adhesion to the substrate. These improvements in the films' structure and properties may be attributed to the intense and energetic ion bombardment taking place during the deposition process. During BP-HiPIMS operation, there is no net increase in the deposition rate as compared to the monopolar regime due to the re-sputtering process. Highlights • Copper thin films were deposited on Si substrates by bipolar pulse HiPIMS technique. • The ICCD images reveal a plasma deconfinement process during bipolar HiPIMS. • The reverse target voltage provides a wide range of ion energies and fluxes. • The energy-enhanced deposition process occurs for reverse voltage above 100 V. • The films exhibit smooth surfaces, dense microstructure and good adhesion. [ABSTRACT FROM AUTHOR]

[Display omitted] • WO 3 modification of air-formed TiO 2 significantly enhances its photoactivity. • Laser treatment improves surface homogeneity and enhances its oxygen deficiency. • Laser-treated composite (L-WO 3 /TiO 2) exhibits lower flat band potential. • L-WO 3 /TiO 2 ensures faster kinetics and more cathodic onset potential of O 2 evolution. • At L-WO 3 /TiO 2 , UV-assisted methanol anodic oxidation is strongly enhanced. The effectiveness of the electrochemical WO 3 -modification as a method for improving the photoactivity of native air-formed TiO 2 layers was assessed. The way in which a mild laser treatment influences the photoelectrochemical performances of the thus obtained WO 3 /TiO 2 systems was also investigated. At laser-treated electrodes (L-WO 3 /TiO 2), the melting-solidification process induced by the treatment led to a smaller size of the deposited WO 3 particles and to their better dispersion on the surface. The treatment also enhanced the surface oxygen deficiency and ensured better relative absorptivity of the oxygenated species on the surface. These features, together with the intrinsic narrower bandgap of the WO 3 -TiO 2 composites, the higher donor density and the lower flat band potential of L-WO 3 /TiO 2 enabled faster kinetic of the oxygen photoanodic evolution. Importantly, the same process exhibited a cathodic shift of its onset potential. The laser treatment also strongly enhanced the photoelectrocatalytic performances for UV-assisted methanol anodic oxidation. [ABSTRACT FROM AUTHOR]

Cu 2 ZnSnS 4 (CZTS) is regarded as one of the emerging materials for next-generation thin film solar cells. However, its synthesis is complex, and obtaining a single-phase CZTS thin film is difficult. This work reports the elaboration of Cu 2 ZnSnS 4 thin films by a sequential magnetron sputtering deposition of Cu 2 SnS 3 (CTS) and ZnS as stacked films. Initially, the CTS films were prepared on a soda lime glass substrate by annealing Cu and SnS 2 stacked layers. Second, ZnS was deposited by magnetron sputtering on the CTS films. The CTS\ZnS stacks were then annealed in Sn + S or S atmospheres. The tetragonal CZTS structure was obtained and confirmed by grazing incidence X-ray diffraction and Raman spectroscopy. The morphological and compositional characteristics, measured by scanning electron microscopy and energy-dispersive spectroscopy, revealed large grains and dense surfaces with the elemental composition close to the intended stoichiometry. Additional X-ray photoemission spectroscopy measurements were performed to determine the surface chemistry and particularities of the obtained films. The optical properties, determined using conventional spectroscopy, showed optimal absorber layer band gap values ranging between 1.38 and 1.50 eV. The electrical measurements showed that all the films are p-type with high carrier concentrations in the range of 10 15 to 10 20 cm -3 . This new synthesis route for CZTS opens the way to obtain high-quality films by an industry-compatible method., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Reduced activation ferritic and martensitic steel like EUROFER (9Cr-1W) are considered as potential structural materials for the first wall of the future next-generation DEMOnstration Power Station (DEMO) fusion reactor and as a reference material for the International Thermonuclear Experimental Reactor (ITER) test blanket module. The primary motivation of this work is to study the re-deposition of the main constituent materials of EUROFER, namely tungsten (W), iron (Fe), and chromium (Cr), in a DEMO type reactor by producing and analyzing complex W x Cr y Fe 1-x-y layers. The composite layers were produced in laboratory using the thermionic vacuum arc (TVA) method, and the morphology, crystalline structure, elemental composition, and mechanical properties were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-X-ray fluorescence (micro-XRF), and glow discharge optical emission spectrometry (GDOES), as well as nanoindentation and tribology measurements. The results show that the layer morphology is textured and is highly dependent on sample positioning during the deposition process. The formation of polycrystalline W x Cr y Fe 1-x-y was observed for all samples with the exception of the sample positioned closer to Fe anode during deposition. The crystalline grain size dimension varied between 10 and 20 nm. The composition and thickness of the layers were strongly influenced by the in-situ coating position, and the elemental depth profiles show a non-uniform distribution of Fe and Cr in the layers. The highest hardness was measured for the sample positioned near the Cr anode, 6.84 GPa, and the lowest was 4.84 GPa, measured for the sample positioned near the W anode. The tribology measurements showed an abrasive sliding wear behavior for most of the samples with a reduction of the friction coefficient with the increase of the normal load.