Search Results (642)

Beta-gallium oxide (β-Ga₂O₃) is a semiconductor with an ultra-wide bandgap, high optical transparency, and excellent electrical properties, which can be finely tuned for a wide range of electronic devices. This study optimized the process conditions for fabricating β-Ga₂O₃ thin films with desired electrical characteristics. β-Ga₂O₃ films were deposited on (100) Si substrates via RF magnetron sputtering with varying O₂ flow rates and post-annealed at temperatures ranging from 600 °C to 800 °C. The structural and electrical properties of the films were analyzed using X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), and Hall effect measurements. The XRD results confirmed the formation of nanocrystalline β-Ga₂O₃, with variations in peak intensities and shifts observed based on O₂ flow rates. The films exhibited carrier concentrations exceeding 5 × 10²² cm⁻³, mobilities ranging from 50 to 115 cm²/Vs, and resistivity around 1 × 10⁻⁶ Ω⋅cm. This study demonstrates that the electrical properties of β-Ga₂O₃ thin films can be modulated during the deposition and post-annealing processes. The ability to control these properties underscores the potential of β-Ga₂O₃ for advanced applications in high-performance high-power devices and optoelectronic devices such as deep ultraviolet photodetectors. Full article

Particle accelerators are powerful tools in fundamental research, medicine, and industry that provide high-energy beams that can be used to study matter and to enable advanced applications. The state-of-the-art particle accelerators are fundamentally constructed from superconducting radio-frequency (SRF) cavities, which act as resonant structures for the acceleration of charged particles. The performance of such cavities is governed by inherent superconducting material properties such as the transition temperature, critical fields, penetration depth, and other related parameters and material quality. For the last few decades, bulk niobium has been the preferred material for SRF cavities, enabling accelerating gradients on the order of ~50 MV/m; however, its intrinsic limitations, high cost, and complicated manufacturing have motivated the search for alternative strategies. Among these, sputter-deposited superconducting thin films offer a promising route to address these challenges by reducing costs, improving thermal stability, and providing access to numerous high-T_c superconductors. This review focuses on progress in sputtered superconducting materials for SRF applications, in particular Nb, NbN, NbTiN, Nb₃Sn, Nb₃Al, V₃Si, Mo–Re, and MgB₂. We review how deposition process parameters such as deposition pressure, substrate temperature, substrate bias, duty cycle, and reactive gas flow influence film microstructure, stoichiometry, and superconducting properties, and link these to RF performance. High-energy deposition techniques, such as HiPIMS, have enabled the deposition of dense Nb and nitride films with high transition temperatures and low surface resistance. In contrast, sputtering of Nb₃Sn offers tunable stoichiometry when compared to vapour diffusion. Relatively new material systems, such as Nb₃Al, V₃Si, Mo-Re, and MgB₂, are just a few of the possibilities offered, but challenges with impurity control, interface engineering, and cavity-scale uniformity will remain. We believe that future progress will depend upon energetic sputtering, multilayer architectures, and systematic demonstrations at the cavity scale. Full article

A compact electrochemical sensor module for pH detection was developed for potential integration into specialized devices used for live cell or tissue incubation, for applications in highly parallelized cell culture analysis, by incorporating Organ-on-Chip devices. This research focuses on the deposition, structural and chemical analysis, and functional characterization of different titanium-oxide layers with various compositions as potentially sensitive materials for pH sensing applications. The titanium-oxide layers were deposited using vacuum sputtering and atomic layer deposition at 100 °C and 300 °C, respectively. Transmission electron microscopy and X-ray photoelectron spectroscopy were utilized to determine the specific composition and structure of different titanium-oxide layers. These TiO_x-functionalized electrodes were connected to the application-specific analog front-end chip of the low-power readout circuit for precise evaluation. The pH sensitivity of the differently modified electrodes, employing various TiO_x materials, was evaluated using pH calibration solutions ranging from pH 6 to 8. Among the various deposition solutions, such as sputtering or high-temperature atomic layer deposition, the TiO_x layer deposited using low-temperature atomic layer deposition proved more suitable for pH sensing applications, with a sensitivity of 54.8–56.7 mV/pH, which closely approximates the Nernstian response. Full article

In this paper, silver oxide (AgO) and copper oxide (CuO) coatings are placed on a single sputtering target with the direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HIPIMS) methods. All the tested coatings are obtained in a reactive process using a metallic target made by the Kurt Lesker company. The investigated coatings are deposited at room temperature on substrates made of pure iron (ARMCO) and polypropylene (PP) without substrate polarization. The deposition time for all the coatings is the same. The results of SEM and TEM investigations clearly show that using the HIPIMS method for the deposition of AgO and CuO coatings reduces their thickness and increases their structure density. Coatings produced with the HIPIMS method are characterized by a higher hardness and Young’s modulus. The value of hardness for AgO and CuO coatings deposited by the HIPIMS method is around 50% higher for AgO coatings and around 24% higher for CuO coatings compared to the coatings obtained by the DC method. This is also true of Young’s modulus values, which are around 30% higher for AgO coatings and 15% higher for CuO coatings produced by the HIPIMS method compared to those of coatings obtained with the DC method. AgO and CuO coatings deposited with both the methods (HIPIMS and DCMS) showed 100% reduction in the viability of two reference laboratory bacteria strains—Escherichia coli (Gram−) and Staphylococcus aureus (Gram+)—on both types of substrates. Additionally, these coatings are characterized by their hydrophobic properties, which means that they can create a protective barrier, making it difficult for bacteria to stick to the surface, limiting their development and preventing the phenomenon of biofouling. The HIPIMS technology allows for the deposition of coatings with better mechanical properties than those produced with the DCMS method, which means that they are more resistant to brittle fractures and wear and have very good antimicrobial properties. Full article

In the present study, copper (Cu) films were deposited on polyethylene terephthalate (PET) substrates using direct-current (DC) magnetron sputtering technology. A systematic investigation was conducted on the effects of process parameters, such as target power, gas flow rate, and substrate temperature, on the microstructure and properties of copper films. The results showed that an increase in the target power resulted in enhanced film grain size, accompanied by a reduction in resistivity and an improvement in adhesion strength. Furthermore, resistivity increased monotonically with elevated gas flow rates, whereas the adhesion strength was found to achieve its maximum at a flow rate of 350 mL/min. In addition, substrate temperature variations had negligible influence on the film grain size and resistivity; nevertheless, the adhesion progressively decreased with increasing substrate temperature. A set of optimal parameters (3 kW, 350 mL/min, −15 °C) was determined based on the comprehensive evaluation of deposition efficiency, conductivity and adhesion performance. The Cu film prepared under these conditions exhibited low resistivity (8.37 × 10⁻⁸ Ω·m) and improved adhesion strength (166 gf/mm). Therefore, it is concluded that high performance of metallized Cu films could be achieved by fine-tuning deposition parameters. Full article

Due to the exceptional corrosion resistance, chemical stability, and dense microstructure, carbon-based thin films are extensively employed in hydrogen energy systems. This study employed magnetron sputtering to fabricate amorphous carbon (a-C) films on SS316L substrates, aiming to improve the corrosion resistance of bipolar plates (BPs) in proton exchange membrane fuel cells (PEMFCs). Using a Taguchi design, the effects of working pressure, sputtering power, substrate bias, and deposition time on film properties were systematically examined and optimized. Films were examined via field emission scanning electron microscopy (FE-SEM), contact angle measurements, and electrochemical tests. Comprehensive evaluation by the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method identified optimal conditions of 1.5 Pa pressure, 150 W radio frequency (RF) power, −250 V bias voltage, and 60 min deposition, yielding dense, uniform films with a corrosion current density of 1.61 × 10⁻⁶ A·cm⁻² and a contact angle of 106.36°, indicative of lotus leaf-like hydrophobicity. This work enriches the theoretical understanding of a-C film process optimization, offering a practical approach for modifying fuel cell bipolar plates to support hydrogen energy applications. Full article

Silver thin films are widely utilized in plasmonic, electronic, and catalytic devices due to their excellent conductivity, optical properties, and surface activity. However, the nanostructure and performance of Ag films are highly dependent on deposition parameters, particularly during radio-frequency magnetron sputtering (RF-MS). In this study, we systematically investigate the effects of RF power, sputtering time, and substrate type on the growth behavior, crystallinity, and electrical conductivity of Ag films. Optical emission spectroscopy (OES) and Langmuir probe diagnostics were employed to analyze the plasma environment, revealing the evolution of electron temperature and plasma density with varying RF powers. Structural characterizations using XRD, SEM, and AFM demonstrate that higher RF power results in reduced grain size, increased film density, and improved crystallinity, while deposition time influences film thickness and grain coalescence. Substrate material also plays a key role, with Cu substrates promoting better crystallinity due to improved lattice matching. Electrical measurements show that denser films with larger grains exhibit lower sheet resistance. These findings provide a comprehensive understanding of the plasma–film interplay and offer strategic insights for optimizing silver nanofilms in high-performance optoelectronic and catalytic systems. Full article

Aluminum nitride (AlN), a III-V wide-bandgap semiconductor, has attracted significant attention for high-temperature and high-power applications. However, achieving p-type doping in AlN remains challenging. In this study, p-type AlN thin films were fabricated via magnetron sputtering using Mg-Al alloy targets with varying Mg concentrations (0.01 at.%, 0.02 at.%, and 0.5 at.%), followed by ex situ high-temperature annealing to facilitate Mg diffusion and electrical activation. The structural, morphological, and electrical properties of the films were systematically characterized using X-ray diffraction (XRD), white light interferometry (WLI), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Hall effect measurements. The results demonstrate that at a Mg doping concentration of 0.02 at.%, the films exhibit optimal crystallinity, uniform Mg distribution, and a favorable balance between carrier concentration and mobility, resulting in effective p-type conductivity. Increasing Mg doping leads to higher surface roughness and the formation of columnar and conical grain structures. While high Mg doping (0.5 at.%) significantly increases carrier concentration and decreases resistivity, it also reduces mobility due to enhanced impurity and carrier–carrier scattering, negatively impacting hole transport. XPS and EDS analyses confirm Mg incorporation and the formation of Mg-N and Al-Mg bonds. Overall, this study indicates that controlled Mg doping combined with high-temperature annealing can achieve p-type AlN films to a certain extent, though mobility and carrier activation remain limited, providing guidance for the development of high-performance AlN-based bipolar devices. Full article

In this study, silicon carbide (SiC) thin films for resistive random-access memory (RRAM) devices were successfully prepared using the radio-frequency magnetron sputtering method at deposition powers of 50 and 75 W for 1 h. The aluminum (Al) top electrode of the RRAM devices was also fabricated using thermal evaporator deposition. Additionally, the electrical properties of the SiC thin film RRAM devices were determined using a B2902A mechanism. The current–voltage (I–V) curves of the as-deposited SiC thin films at 50 and 75 W power levels were measured and analyzed. Specifically, the set and reset voltages for the RRAM devices deposited at 50 and 75 W were approximately 1.2 and −1.5 V, respectively. For the annealed samples, the memory windows of the 75 W SiC thin film RRAM devices treated at 300 °C were found to be around 10⁵. Full article

In this study, the electrochemical corrosion behavior of TiAlZrTaNb nitride thin films deposited on 304 stainless steel substrates was investigated. The thin films were synthesized using high-power impulse magnetron sputtering (HiPIMS) and are classified as high-entropy alloys (HEAs). The microstructure, morphology, and chemical composition of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), respectively. Corrosion resistance was evaluated through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests, employing tap water, acetic acid, and citric acid solutions at room temperature as electrolytes. The results demonstrated that the TiAlZrTaNbN coating exhibits a dense and homogeneous structure with a uniform elemental distribution. XRD analysis revealed the presence of face-centered cubic (FCC) crystalline phases, which significantly contribute to the coating’s corrosion resistance. Furthermore, the coating displayed exceptional corrosion performance in both acetic acid and citric acid electrolytes—simulating food environments with a pH ≤ 4.5—as revealed by a substantial reduction in corrosion current density and a positive shift in corrosion potential. These findings provide valuable insights into the properties of TiAlZrTaNbN coatings and underscore their potential for enhancing the durability of mechanical components employed in the food industry. Full article

The continuous discharge voltage waveform and phenomena between the electrode and substrate were explored in this paper to study the ultrasonic electro-spark deposition process. Additionally, the impact of ultrasonics on the ultrasonic electro-spark deposition process and the properties of the deposition layer were examined. The results show that the charge–discharge frequency of the ultrasonic electro-spark deposition process was commensurate with the discharge frequency of the ultrasonic electro-spark deposition power source, and the voltage waveform was stable. When ultrasonics is introduced, the molten droplet spray trajectory is efficiently guided, resulting in the spark spray trajectory displaying notable directional concentration characteristics. During a single charging and discharging phase, the electrode and substrate made roughly 15 mechanical contacts, 1 of which was discharging, and the remaining 14 were mechanically contacted reinforcement. The surface of the ultrasonic electro-spark deposition layer exhibited a sputtering morphology with no surface cracks. Phase structures such as Co₃W₃C, Fe₃W₃C, Fe₆W₆C, WC, and W₂C constituted the majority of the ultrasonic electro-spark deposition layer’s microstructure and showed strong metallurgical bonds with the substrate. The ultrasonic electro-spark deposition layer has a surface roughness of 2.554 μm, a cross-section porosity of 1.3%, and a maximum microhardness of 1038.8 HV_0.025. Comparative analysis demonstrates that the addition of ultrasonics can significantly enhance the deposition layer’s quality and performance. When compared to the electro-spark deposition layer, the surface roughness of the ultrasonic electro-spark deposition layer decreases by roughly 61.4%, the cross-sectional porosity decreases by around 57.5%, and the maximum microhardness increases by about 15.5%. Many cracks and much high surface roughness in the conventional electro-spark deposition layer are resolved by the ultrasonic electro-spark deposition technique, which is crucial for cold drawing mold surface strengthening. Full article

In this study, SiO₂ thin films were sputtered from a Si target using reactive HiPIMS (high-power impulse magnetron sputtering) in an argon–oxygen process gas. In order to understand the behavior of HiPIMS, the deposition process was studied by systematically varying the sputtering parameters and monitoring the current waveforms. A decaying transient was observed at the leading edge of the pulse, caused by the L-C term of the HiPIMS generator, the cable, and the target. To investigate the periodic transient, we used, to the best of our knowledge, for the first time, a standing wave ratio meter (SWR). In order to be able to deposit films with the desired properties, the target voltage and its associated current characteristics were also investigated. The formation of a distinct step-like shape in the current–voltage characteristics is observed during reactive sputtering. A simple physical model was used to determine the position and length of the plateau. The appearance of hysteresis, which is typical of reactive sputtering, was also observed. These findings may help us to better understand the mechanism of reactive HiPIMS deposition of SiO₂. Full article

By integrating cathodic arc evaporation (CAE) with magnetron sputtering (MS) or high-power impulse magnetron sputtering (HiPIMS), hard coatings with diverse multicomponent compositions can be fabricated. Depending on the deposition conditions, the coatings with nano-composite or nano-multilayered microstructures are produced. During the mixing deposition conditions, nano-composite coatings are fabricated, which can be tailored to possess combining properties of super hardness, low friction coefficient, and excellent thermal/chemical stability. For the deposition with larger rotating periods, layer-by-layer deposition was observed. By the nano-multilayered coating design, superior mechanical properties (hardness ≥ 35 GPa), modulated residual stresses, and enhanced high-temperature properties can be obtained. In addition, lubricious elements, low friction (friction coefficient < 0.4), and low wear (<10⁻⁵ mm³/N∙m) both at ambient temperature and high temperature can be realized. Among these coatings, some have been specifically designed to achieve outstanding cutting performance in high-speed cutting applications. Several nitride and oxide hard coatings, such as AlTiN, TiAlN/TiSiN, AlCrN/Cu, and AlCrO, were deposited using a hybrid industrial physical vapor deposition (PVD) coating system. The microstructure, mechanical properties, and cutting performance of these coatings will be discussed. Full article

Aluminum nitride (AlN) is a material of wide interest in the optoelectronics and high-power electronics industry. The deposition of AlN thin films at elevated temperatures is a well-established process, but its implementation on flexible substrates with conductive oxides, such as ITO-glass or ITO-PET, poses challenges due to the thermal degradation of these materials. In this work, the deposition and characterization of AlN thin films by reactive sputtering at a low temperature (RT and 100 °C) on ITO-glass and ITO-PET substrates are presented. The structural, optical, and electrical properties of the samples have been analysed as a function of the sputtering power and the deposition temperature. XRD analysis revealed the absence of peaks of crystalline AlN, indicative of the formation of an amorphous phase. EDX measurements performed on the ITO-glass substrate with a radiofrequency power applied to the Al target of 175 W confirmed the presence of Al and N, corroborating the deposition of AlN. SEM analyses showed the formation of homogeneous and compact layers, and transmission optical measurements revealed a bandgap of around 5.82 eV, depending on the deposition conditions. Electrical resistivity measurements indicated an insulating character. Overall, these findings confirm the potential of amorphous AlN for applications in flexible optoelectronic devices. Full article

Graphene/h-BN/Si heterostructures show considerable potential for future use in infrared detection and photovoltaic technologies due to their adjustable electrical behavior and well-matched interfacial structure. The near-lattice match between graphene and hexagonal boron nitride (h-BN) enables the deposition of low-defect-density graphene on h-BN surfaces. This study presents a thorough exploration of the low-frequency electrical noise behavior of graphene/h-BN/Si heterojunctions under both forward and reverse bias conditions at room temperature. Graphene nanolayers were directly grown on h-BN films using microwave plasma-enhanced CVD. The h-BN layers were formed by reactive high-power impulse magnetron sputtering (HIPIMS). Four h-BN thicknesses were examined: 1 nm, 3 nm, 5 nm, and 15 nm. A reference graphene/Si junction (without h-BN) prepared under identical synthesis conditions was also studied for comparison. Low-frequency noise analysis enabled the identification of dominant charge transport mechanisms in the different device structures. Our results demonstrate that grain boundaries act as dominant defects contributing to increased noise intensity under high forward bias. Statistical analysis of voltage noise spectral density across multiple samples, supported by Raman spectroscopy, reveals that hydrogen-related defects significantly contribute to 1/f noise in the linear region of the junction’s current–voltage characteristics. This study provides the first in-depth insight into the impact of h-BN interlayers on low-frequency noise in graphene/Si heterojunctions. Full article