Search Results (394)

This study delivers a comprehensive evaluation of tantalum-based coatings designed as protective surface layers for cardiovascular stents, focusing on their mechanical durability, corrosion resistance, and surface properties relevant to hemocompatibility. Coatings consisting of tantalum (Ta), tantalum oxide (Ta₂O₅), and a bilayer Ta/Ta₂O₅ system were deposited onto 316L stainless steel using plasma-assisted reactive magnetron sputtering. Structural characterization confirmed a nanocrystalline β-phase for Ta, while Ta₂O₅ exhibited an amorphous, dense, grain-boundary-free morphology that provided superior crack resistance together with enhanced corrosion protection. The bilayer configuration demonstrated the highest overall performance by combining the hardness and mechanical support of Ta with the chemical inertness and stability of Ta₂O₅. This architecture achieved the greatest hardness (861.5 HV), improved toughness proxies expressed as H/E = 0.08 and H³/E² = 0.06 GPa, and a favorable modulus gradient that effectively reduced interfacial stress and increased adhesion. Electrochemical testing in Hanks’ Body Fluid showed a dramatic 1000-fold reduction in corrosion current when compared with uncoated stainless steel, surpassing the performance of both individual monolayers. Assessments of surface properties further demonstrated that hydrophilic, oxide-rich surfaces limited protein adsorption and platelet activation, with Ta₂O₅ and Ta/Ta₂O₅ coatings performing strongly. Overall, these findings indicate that Ta/Ta₂O₅ bilayers provide a multifunctional surface solution for next-generation stents. Full article

In the current work, the microstructural evolution and CO₂ sensing performance of tungsten trioxide (WO₃) thin films synthesized by reactive DC magnetron sputtering are investigated. Three specific thicknesses of 42, 66, and 131 nm were obtained and annealed at 500 °C, resulting in a stable monoclinic P2₁/n phase with a strong (200) preferred orientation. Gas sensing tests toward 10,000 ppm of CO₂ revealed that the 42 nm film achieves the highest sensitivity (92%) at an optimal operating temperature of 300 °C. Rietveld refinement and texture analysis (texture index, J) demonstrate that the superior performance of the thinnest film is driven by a synergy between its high surface porosity, a grain size comparable to the Debye length, and a high density of active sites on the (200) plane. While all films exhibit n-type semiconductor behavior, increasing thickness leads to microstructural densification and reduced texture, which hinders gas diffusion and operational stability. These findings establish thickness control as a critical parameter for engineering high-performance WO₃-based CO₂ sensors. Full article

The suppression of residual reflectivity in optical elements has become a hot research topic as it addresses the degradation of optical system imaging quality caused by stray light. Antireflective coatings on the outer surface of window glasses require low reflectivity, high hardness, and resistance to mechanical wear. This study investigates the role of reactive gas stoichiometry in tailoring the structure and performance of ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ antireflection (AR) coatings deposited on GG7i glass via capacitively coupled radio-frequency magnetron sputtering. First, the influence of three ${\mathrm{N}}_2$/${\mathrm{O}}_2$ flow ratios on the optical and mechanical properties of ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ films discussed under identical process parameters. Results show that the refractive index, hardness, and surface roughness of the ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ films increase with increasing ${\mathrm{N}}_2$/${\mathrm{O}}_2$ ratio and that the stress of the ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ films increases according to the Stoney formula. The wear resistance of the ${\mathrm{SiO}}_x$${\mathrm{N}}_y$ films combined with an antifingerprint (AF) coating is tested using steel wool. Experimental results show that the water contact angle of the AF decreases with increasing surface roughness of the film. Finally, on the basis of a comprehensive evaluation of optical and mechanical properties, the antireflection coating on the outer surface of the window glass was prepared by optimizing the process parameters. At $0^{°}$ incidence, the average reflectivity from 420 to 680 nm is <1%, the maximum value is <1.2%, the surface hardness is 17.2 GPa, and the water contact angle is ${100}^{°}$ after the steel wool wear test, showing its suitability for durable antifingerprint applications. This work provides a strategic pathway for designing high-performance optical coatings with tailored mechanical robustness. Full article

In this study, reactive radio frequency magnetron sputtering was used to deposit thin films. Gadolinium oxide was deposited on titanium nitride substrates at different deposition times and oxygen concentrations. Next, rapid thermal annealing and supercritical fluid treatment were performed. The three-dimensional profiler (alpha-step), X-ray diffractometer, and X-ray photoelectron spectroscopy were used to measure the thickness, surface morphology, crystal structure, and element analysis. Then, indium tin oxide was sputtered and deposited on the gadolinium oxide, which was covered with the metal mask to form a top electrode, thereby manufacturing a metal/insulator/metal resistive memory structure. Finally, a power meter was used to measure the characteristics of the resistive random access memory, including the current–voltage characteristics, and to explore the leakage current conduction mechanism and component durability. Full article

Given the increasing environmental degradation, this study investigates advanced zinc oxide (ZnO)-based materials for the mineralization of toxic compounds through the combined action of photo- and piezocatalysis. Two complementary strategies were employed to enhance catalytic efficiency. First, ZnO_1−xN_x thin films were deposited by reactive high-power impulse magnetron sputtering (R-HiPIMS) to reduce the band gap energy. Second, flower-like ZnO nanostructures were synthesized using the pulsed thermionic vacuum arc (p-TVA) technique to increase the specific surface area. Both systems were further modified by decoration with Ag₂O nanoparticles to improve charge separation. The R-HiPIMS technique offers significant advantages in terms of precise control over processing parameters, enabling accurate tuning of film properties, including microstructure, chemical composition, and electronic structure. However, films produced via R-HiPIMS generally exhibit lower photo-piezocatalytic activity compared to nanostructured counterparts, primarily due to their comparatively reduced effective surface area and limited charge separation efficiency. In contrast, the p-TVA technique enables the synthesis of nanostructured thin films with substantially enhanced photo-piezocatalytic performance. This improvement is attributed to the increased effective surface area and the promotion of more efficient electron–hole pair separation. The materials were comprehensively characterized in terms of optical properties (UV–Vis spectroscopy), chemical composition and bonding (XPS), crystalline structure (XRD), surface morphology (FE-SEM), and photo-piezocatalytic performance. Catalytic activity was evaluated via the degradation of methylene blue (MB) under visible light irradiation and mechanical vibrations. Nitrogen incorporation in ZnO_1−xN_x thin films led to an increase in photocatalytic efficiency from 20% to 28.7%, while the simultaneous application of light and mechanical stimulation increased efficiency to approximately 50%. Under identical irradiation conditions, Ag₂O-decorated ZnO and Ag₂O-decorated ZnO_1−xN_x exhibited photo-degradation reaction rate constants up to 65% higher than bare counterparts, attributed to reduced electron–hole recombination. ZnO nanostructures achieved degradation efficiencies of 59%, rising to 88.3% with Ag₂O decoration under solar illumination for 120 min. When combined with mechanical vibrations, after 60 min, the degradation efficiencies reached 93% for ZnO and 98% for Ag₂O/ZnO systems. A photodegradation mechanism of Ag₂O NPs-decorated ZnO heterostructures was proposed. Full article

Physicochemical modification of titanium implants aims to enhance early osseointegration by improving bioactivity. This study deposited and evaluated an anatase TiO₂ film on clinically relevant sandblasted, acid-etched titanium (Ti-SLA) to enhance in vitro bioactivity and osteogenic responses. An ~8 µm TiO₂-anatase coating was deposited on Ti-SLA by reactive pulsed DC magnetron sputtering. Surface characterization included FE-SEM, helium ion microscopy, and XRD. Wettability and surface free energy (SFE) were evaluated by contact angle analysis. In vitro bioactivity was assessed by hydroxyapatite (HA) formation in twofold-concentrated simulated body fluid (2× SBF). Osteoblast responses were evaluated through cell adhesion, viability, alkaline phosphatase activity, gene expression, and mineralization. The coating produced hierarchical multi-globular microstructures decorated with faceted anatase nanocrystals. Ti-SLA’s initial hydrophobicity converted to a superhydrophilic, high-energy surface with increased polar SFE. Homogeneous HA crystallites deposited exclusively on SLA-anatase in 2× SBF. SAOS-2 cells showed enhanced metabolic activity, ALP activity, osteogenic gene upregulation, and improved mineralized matrix, while primary human osteoblasts exhibited increased metabolic activity and calcium deposition. The anatase coating produced a superhydrophilic, high-energy micro-nano surface that accelerates HA formation and enhances osteoblast function in vitro, warranting in vivo validation for early osseointegration. Full article

Stainless-steel nitride thin films were deposited onto silicon substrates at different temperatures ranging from 150 to 600 °C using reactive magnetron sputtering. The influence of substrate temperature on nitrogen incorporation, surface roughness, microstructure, and mechanical properties was systematically investigated. X-ray photoelectron spectroscopy (XPS) analysis showed that the nitrogen content increased with substrate temperature, reaching a maximum value of 34 wt.% at 350 °C, while at higher substrate temperatures (450–600 °C), the nitrogen content decreased. X-ray diffraction analysis revealed that the coating structure strongly depends on the substrate temperature. At temperatures above 450 °C, the films comprise a multiphase structure consisting of CrN, bcc-Fe, and Ni. In contrast, films deposited below 450 °C are dominated by the S-phase, corresponding to a nitrogen-supersaturated fcc structure. Scanning electron microscopy (SEM) analyses confirmed microstructural evolution with substrate temperature, showing fine, compact grains at lower temperatures and coarser structures at higher temperatures. Surface roughness measured by a profilometer exhibited a minimum at 350 °C. The mechanical performance of the films was evaluated using micro-Knoop hardness measurements, together with the calculated elastic strain indicator (H/E) and resistance to the plastic deformation parameter (H³/E²). The results showed that hardness and these mechanical indicators reached their maximum values at a substrate temperature of 350 °C. These findings provide valuable insight into the deposition–structure–property relationships of stainless-steel nitride thin films for wear-resistant and protective coating applications. Full article

This paper presents a study on the development and optimisation of thin films of nickel-vanadium oxide (NiV_xO_y) deposited by DC reactive magnetron sputtering (RMS) controlled by P.E.M. (plasma emission monitoring). The hysteresis behaviour of the Ni emission signal as a function of oxygen incorporation was analysed using optical emission spectroscopy (OES), enabling the identification of critical working points along the hysteresis loop and their correlation with film growth mechanisms. Compared to the non-monotonic nature of the target discharge voltage signal, OES provided a simplified response for real-time process control. A set of coatings was deposited under various working pressures (0.6 and 2.0 Pa) and plasma emission monitoring (P.E.M.) conditions and was thoroughly characterised in terms of microstructure, composition, optical modulation, and electrochemical performance. Films deposited at high pressure and under 30% P.E.M. conditions showed an optimal balance between optical modulation (21%) and charge density (4 mC/cm²), which was attributed to the increased Ni³⁺ content and the surface cracks at low density. Full article

Niobium nitride (δ-NbN) coatings were deposited on AISI 316L austenitic steel using reactive DC magnetron sputtering. This study investigates the effects of air oxidation on the surface morphology, topography, roughness, nanohardness, adhesion, and wear resistance of NbN coatings. Their microstructure and thickness were analyzed by scanning electron microscopy (SEM), while surface morphology and roughness were assessed using atomic force microscopy (AFM), and surface topography was assessed by an optical profilometer. Nanohardness was measured using a Berkovich indenter. Adhesion was evaluated via progressive-load scratch testing and Rockwell indentation (VDI 3198 standard). Wear resistance was assessed using the “ball-on-disk” method. Both as-deposited and oxidized NbN coatings improved the mechanical performance of the substrate surface. Air oxidation led to the formation of an orthorhombic Nb₂O₅ surface layer, which increased surface roughness and reduced hardness. However, the brittle oxide also contributed to a lower coefficient of friction. Despite reduced adhesion and increased surface development, the oxidized coating exhibited a significantly lower wear rate than the uncoated steel, though several times higher than that of the non-oxidized NbN. Considering its good wear and corrosion performance, along with the bioactivity confirmed in earlier research, the oxidized NbN coating can be considered a promising candidate for biomedical applications. Full article

Tool steels are critical for high-load applications, e.g., forging and metal-forming, where they face thermal cracking, fatigue, erosion, and wear. This study evaluates the impact of gas nitriding and S-phase PVD coatings on the mechanical and tribological properties of four tool steels: 40CrMnNiMo8-6-4, 60CrMoV18-5, X50CrMoV5-2, and X38CrMoV5-3. Samples were heat-treated (quenched and tempered at 600 °C), then gas-nitrided at 575 °C for 6 h with nitriding potentials (Kn) of 0.18, 0.79, or 2.18, or coated via reactive magnetron sputtering in Ar/N₂ or Ar/N₂/CH₄ atmospheres at 200 °C or 400 °C. Characterization involved XRD, LOM, FE-SEM, GDOES, Vickers hardness (HV0.1), and ball-on-disk wear testing with Al₂O₃_ counter-samples. Gas nitriding produced nitrogen diffusion layers (80–200 μm thick) and compound layers (ε-Fe_(2-3)N, γ’-Fe₄N) at higher Kn, increasing hardness by 80–100% (up to 1100 HV0.1 for steel X38CrMoV5-3). S-phase coatings (1.6–3.6 μm thick) formed expanded austenite with varying N content, achieving comparable hardness (up to 1100 HV0.1) in high-N₂ atmospheres, alongside substrate diffusion layers. Both types of treatment enhance load-bearing capacity, adhesion, and durability, offering superior wear resistance compared to conventional PVD coatings and addressing demands for extended tool life in industrial applications. Full article

TiO_xN_y coatings are known for their good biocompatibility and corrosion resistance and have been previously explored for biomedical applications, including cardiovascular stents. In this work, emphasis is placed on a systematic investigation of the effect of substrate bias voltage on the structural, morphological, and mechanical properties of TiO_xN_y films deposited by reactive magnetron sputtering. TiO_xN_y coatings were deposited on 316L stainless steel substrates using a pure titanium target (99.99%) in an Ar–N₂–O₂ gas mixture at various substrate bias voltages (0 to −150 V). The influence of substrate bias on the deposition rate, structure, and mechanical properties of the films was investigated. X-ray diffraction (XRD) analysis revealed the sequential phase evolution from cubic TiN to oxynitride TiON and further to TiO₂ (anatase/rutile) with increasing negative substrate bias, indicating that ion bombardment energy plays a decisive role in determining the crystallinity and phase composition of the coatings. The coating deposited at −50 V exhibited the highest hardness (~430 HV) and good adhesion strength (critical load 20–25 N). Contact angle measurements confirmed the hydrophilic behavior of the coatings, which is favorable for biomedical applications. Full article

The effect of the multilayer structure of Cr/CrN coatings deposited by reactive magnetron sputtering on zirconium alloy E110 (Zr–1Nb) on their thermal stability and resistance to steam oxidation at 1100 °C was studied. Coatings with different numbers of alternating Cr and CrN sublayers (1, 2, 4, and 6) were fabricated using experimental methods of X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive analysis (SEM/EDS). It was shown that an increase in the number of alternating Cr and CrN sublayers leads to the preservation of the cubic phase of CrN, the formation of a dense structure, and a decrease in Cr–Zr interdiffusion. After testing, multilayer coatings retaining the internal structure and a sufficiently structurally dense Cr₂O₃ layer effectively ensured air penetration. The best thermal stability was demonstrated by a six-layer coating, ensuring minimal oxidation and preservation of the E110 substrate. Full article

Zinc oxide (ZnO) thin films were deposited by radio-frequency reactive magnetron sputtering at a cryogenic substrate temperature of −78 °C to explore a novel low-thermal-budget route for semiconductor growth. Despite the extremely low temperature, X-ray diffraction revealed spontaneous partial crystallization of wurtzite ZnO upon warming to room temperature, driven by strain relaxation and stress coupling at the ZnO/SiO₂ interface. Atomic-force and scanning-electron microscopies confirmed nanoscale hillock and ridge morphologies that correlate with in-plane compressive stress and out-of-plane tensile strain. Spectroscopic ellipsometry, modeled using a general oscillator (GO) mathematical model approach, determined a film thickness of 60.81 nm, surface roughness of 3.75 nm, and a direct optical bandgap of 3.40 eV. Photoluminescence spectra exhibited strong near-band-edge emission modulated with LO-phonon replicas at 300 K, indicating robust exciton–phonon coupling. This study demonstrates that ZnO films grown at cryogenic conditions can undergo substrate-induced self-crystallize upon warming, which eliminates the need for thermal annealing. The introduced cryogenic self-crystallization regime offers a new pathway for depositing crystalline semiconductors on thermally sensitive or flexible substrates where heating is undesirable, enabling future optoelectronic and photonic device fabrication under ultra-low thermal-budget conditions. Full article

Tantalum nitride (TaN) coatings are valued for their hardness, chemical inertness, and biocompatibility; however, they lack intrinsic antibacterial properties, which limits their application in biomedical environments. Introducing copper (Cu) into the TaN matrix offers a potential solution by combining TaN’s mechanical and chemical durability with Cu’s well-documented antimicrobial action. This study explores how varying copper incorporation affects the structural, electrical, photocatalytic, and antibacterial characteristics of TaCuN multilayer films synthesized via reactive magnetron sputtering. Three thin TaCuN films were fabricated using a high-power reactive magnetron co-sputtering system, varying the Cu target power to control the composition. Structural and morphological analysis was performed using X-ray diffraction (XRD), scanning/transmission electron microscopy (STEM/TEM), and energy-dispersive X-ray spectroscopy (EDS). Electrical conductivity was studied along and across the film surfaces at temperatures ranging from 20 to 375 K using AC impedance spectroscopy. Optical and photocatalytic properties were assessed using UV–Vis spectroscopy and methylene blue degradation tests. Antibacterial activity against Staphylococcus aureus was analyzed under visible light using CFU reduction tests. XRD and TEM analyses revealed a multilayered four-zone architecture with alternating Ta-, Cu-, and N-rich phases and a dominant cubic δ-TaN pattern. The layers exhibited pronounced conductivity anisotropy, with in-plane conductivity (~10³ Ω⁻¹ cm⁻¹) exceeding cross-plane conductivity by ~10⁷ times, attributed to the formation of a metallic conduction channel in the mid-layer. Optical spectra indicated limited light absorption above 300 nm and negligible photocatalytic activity. Increasing the Cu content substantially enhanced antibacterial efficiency, with the highest-Cu sample achieving 95.6 % bacterial growth reduction. Morphological evaluation indicated that smooth film surfaces (Ra < 0.2 μm) effectively minimized bacterial adhesion. Reactive magnetron sputtering enables the precise engineering of TaCuN multilayers, combining high electrical anisotropy with robust antibacterial functionality. The optimized TaCuN coating offers promising potential in biomedical and protective applications where both conductivity and microbial resistance are required. Full article

Yttrium oxide (Y₂O₃) films have been widely used as protective layers in plasma etching equipment, but achieving stoichiometric films with high deposition rates remains a challenge. In this study, Y₂O₃ films were fabricated by a medium-frequency reactive magnetron sputtering (MF-RMS) technique. The oxygen flow and target control voltage were regulated through a closed-loop feedback control system, which effectively solved the problem. The microstructure, mechanical, optical, and plasma etching properties were systematically investigated. The results showed that near-stoichiometric films can achieve a relatively high deposition rate. Increasing the deposition temperature induced a structural transition in the Y₂O₃ film from a predominantly cubic phase to a mixture of cubic and monoclinic phases. For Y₂O₃ films deposited at room temperature, increasing the bias voltage increased the deposition rate but reduced hardness and elastic modulus. The Y₂O₃ film deposited at 300 °C in the near-metallic mode exhibited the highest hardness and elastic modulus, reaching 13.3 GPa and 222.0 GPa, respectively. All Y₂O₃ films exhibited excellent transmittance and resistance to plasma etching. This study provides an effective protective strategy for semiconductor etching chambers. Full article