Search Results (3,774)

Adhesion strength, toughness, and resistance to frictional heating are critical characteristics for suppressing premature coating delamination and protecting the substrate from plastic deformation. This study investigates the synergistic role of intermediate adhesion-promoting layers on the mechanical and tribological performance of diamond-like carbon (DLC) coatings deposited on tool steel substrates via high-power impulse magnetron sputtering (HiPIMS). Nanoindentation and micro-scratch testing were conducted to evaluate single-layer TiAlN, single-layer DLC, and multilayer DLC/TiAlN coating architectures. Owing to the TiAlN interlayer beneath the DLC topcoat, the multilayer DLC/TiAlN system demonstrated superior composite hardness and interfacial adhesion strength. Microstructural characterization via SEM-EDS and Raman spectroscopy confirmed that a dense, columnar TiAlN interlayer with a high aluminum concentration provided vital load-bearing capacity for the overlying DLC film. During dry CNC turning tests on aluminum and steel alloys, the multilayer DLC/TiAlN coating exhibited the lowest cutting forces, cutting temperatures, and surface roughness. The architecture effectively suppressed flank and crater wear, which reduced the chip compression ratio and mitigated plastic shear strain at the tool–chip interface. This synergistic interaction within the DLC/TiAlN coating system minimizes tribological degradation, demonstrating high potential for demanding machining applications. Full article

MoSi₂ coatings are promising protective materials for hot-section components in aerospace applications, where long-term durability is an important concern. Increasing the coating thickness has been proposed as an important strategy for improving their long-term durability. To prepare MoSi₂ coatings with different thicknesses, a Mo precursor layer with a thickness of 30 μm was deposited by direct-current (DC) magnetron sputtering, followed by pack siliconizing at 1300 °C for 3, 5 and 7 h, respectively. The phase composition, thickness, microstructure and mechanical properties were characterized. The results showed that the Mo coating reached a thickness of approximately 30 μm after 18 h of magnetron sputtering, exhibiting a columnar structure without obvious defects. The thicknesses of MoSi₂ coatings were 86.5 μm, 94.7 μm, and 104.3 μm, respectively, showing an approximately linear increase with pack siliconizing time within the investigated range of 3–7 h. The coatings obtained after 3 and 5 h consisted of three sublayers, including an outer MoSi₂ layer, an intermediate (Mo,Nb)₅Si₃-type layer, and an inner Mo/Nb-rich layer. After 7 h, the intermediate layer was no longer clearly distinguishable, and no distinct residual Mo/Nb-rich inner layer was observed. The coating was therefore predominantly composed of MoSi₂, indicating that 7 h represents a practical threshold for essentially complete silicidation of the 30 μm-thick Mo precursor layer under the present conditions. Within the investigated range of 3–7 h, the mean microhardness, elastic modulus and fracture toughness of the MoSi₂ coating increased approximately linearly with pack siliconizing time, with increases of approximately 31.5 HV_0.3, 24.6 GPa and 0.56 MPa·m^1/2, respectively. The results demonstrate that combining a 30 μm-thick Mo precursor layer with subsequent pack siliconizing provides an effective route for fabricating thick MoSi₂-based coatings exceeding 100 μm, together with controllable microstructural evolution and mechanical properties. The potential benefit of such coating thickening for oxidation resistance remains to be verified in future oxidation tests. Full article

A spectrally resolved optical waveguide resonance sensor modified with perovskite film is proposed. The sensor is based on a Kretschmann configuration consisting of a coupling prism, an indium tin oxide (ITO) glass, a gold film, a mesoporous TiO₂ layer, and a perovskite film. In the fabrication process, a gold film was first deposited onto the ITO glass by magnetron sputtering, followed by the deposition of a mesoporous TiO₂ layer via a sol–gel method, and finally a perovskite film was prepared using a two-step process. The thicknesses of the mesoporous TiO₂ and perovskite layers were measured by a scanning electron microscope. Using the measured film thicknesses, the sensor structure was simulated based on Fresnel theory, yielding the resonance spectra. The fitted resonance wavelength is in good agreement with the experimentally measured resonance wavelength, confirming the accuracy of the adopted model. To further evaluate the sensing performance, a four-layer structure (prism/Au/mesoporous TiO₂/analyte) and a five-layer structure (prism/Au/mesoporous TiO₂/perovskite/analyte) were employed to detect different concentrations of ammonia, ethanol, and isopropanol vapors. The experimental results demonstrate that, at an incident angle of 13°, the perovskite-modified sensor exhibits higher sensitivity toward all three vapors compared with the unmodified sensor, achieving a sensitivity of 3.584 nm/(mmol·L⁻¹) for ethanol. Full article

Biomedical-grade stainless steel (316L) is susceptible to corrosion in human body fluids, and the subsequent release of metallic ions may contribute to adverse health effects. Silicon nitride (SiN), a biocompatible material, offers strong adhesion and serves as an effective barrier on metallic substrates, significantly reducing the corrosion rate of 316L stainless steel. The corrosion resistance of the SiN coating is influenced by the sputtering deposition parameters. In this study, SiN thin films were deposited at varying power levels to optimize the corrosion resistance of 316L stainless steel. Surface and electrochemical characterization techniques were employed. The findings demonstrate that the thin film deposited at 60 W exhibits the highest corrosion resistance, attributed to its reduced apparent porosity (1.3%). Full article

Low magnetic damping and narrow ferromagnetic resonance (FMR) linewidth are essential for efficient spin-wave excitation in magnonic devices. We investigate how a combination of deposition techniques, interface engineering, and consequent thermal treatment affects magnetic losses in thin permalloy (Py, Ni₈₀Fe₂₀) films prepared by electron-beam evaporation and magnetron sputtering. Broadband vector network analyzer FMR, atomic force microscopy, and electromagnetic simulations were used to correlate linewidth, surface morphology, and spin-wave excitation. Comparable minimum linewidths were reached by both deposition routes: approximately 23 Oe at 4 GHz for the best electron-beam-evaporated film and approximately 21 Oe for a 20 nm TaN/Py/TaN structure. Electron-beam-evaporated films proved sensitive to substrate choice, surface preparation and—in the absence of plasma cleaning—deposition temperature, whereas the magnetic field applied during growth had only a weak effect. After magnetic annealing, however, only the TaN-encapsulated structure retained its narrow linewidth, while the uncapped films broadened substantially. Simulations further showed that linewidth reduction enhances the excitation efficiency and visibility of standing spin-wave modes. These results indicate that comparable losses are achievable through several process routes, whereas retaining them through thermal processing requires interface engineering—a distinction that matters for integrating Py films into magnonic and spintronic devices. Full article

This study assessed whether surface engineering can improve the durability of metal components in hip joint endoprostheses by reducing friction, abrasive wear, and corrosion at the head–socket interface. Single-layer TiN coatings and multilayer TiN + (Ti,N)₃P + Ti₃P + (Ti,Ni) coatings were deposited on Ti6Al4V alloy using plasma- and PVD-based processes and tested in combination with Chirulen 1020 ultra-high-molecular-weight polyethylene. Tribological performance, surface condition, microstructure, and chemical composition were evaluated before and after wear testing. The results showed that coating type and deposition method influenced the behavior of the friction pair. The most promising systems were Ti6Al4V coated with titanium nitride by sputtering or plasma spraying and Ti6Al4V with the multilayer coating, both paired with Chirulen 1020. The multilayer-coated Ti6Al4V head combined with a Chirulen 1020 cup provided the most favorable friction-pair performance, indicating its potential to reduce wear-product formation and extend implant service life. Full article

Ti owes its clinical durability to a protective passive oxide film; however, repetitive toothbrushing and fluoride exposure may disrupt this interface and increase its susceptibility to tribocorrosion. This in vitro study investigated the electrochemical behaviour and surface integrity of commercially pure titanium (CpTi) grade II coated with Ta₂O₅ or ZrO₂ after simulated toothbrushing. CpTi discs were divided into three groups: CpTi, CpTi/Ta₂O₅, and CpTi/ZrO₂. The coatings were deposited by reactive DC magnetron sputtering. Film thickness and adhesion were assessed by step-height and tape tests. Simulated toothbrushing was performed for 22,080 cycles/2 Hz under a load of 200 gf in either Fusayama artificial saliva (AS) or a fluoridated dentifrice (FD) slurry with AS (1:2 w/w). Surface morphology, elemental composition, topography, roughness, crystalline structure, and wettability were evaluated using SEM/EDS, AFM, XRD, and static and dynamic contact angle (CA) measurements. Electrochemical behaviour was assessed by OCP, EIS, and potentiodynamic polarisation. Toothbrushing induced cyclic OCP shifts consistent with depassivation and repassivation, with surface- and medium-dependent electrochemical responses (p ≤ 0.001). CpTi exhibited a more active electrochemical state, higher i_corr, and more pronounced surface alterations. Both coatings significantly improved i_corr and corrosion rate (CR) (p < 0.001). Ta₂O₅ provided the greatest electrochemical protection, reducing the CR by approximately 95% versus 77% for ZrO₂. Topographical response to F brushing was also surface-dependent (p < 0.001). Roughness was unchanged after corrosion but surface-dependent after toothbrushing (p < 0.001), while wettability increased after corrosion (p ≤ 0.003) and CAH was surface-dependent (p = 0.003). Within the limitations of this in vitro study, Ta₂O₅ and ZrO₂ coatings enhanced the electrochemical response of CpTi under simulated oral-hygiene challenges, with Ta₂O₅ providing the strongest overall protection, suggesting that oxide surface modification is a promising strategy for improving the tribocorrosion behaviour of Ti-based dental materials. Full article

Nickel oxide (NiO_x) thin films are promising p-type transparent semiconductors for optoelectronic and energy-conversion devices. This study investigates the role of radio-frequency (RF) sputtering power in the growth evolution, microstructural development, and functional properties of NiO_x thin films deposited at room temperature. The RF sputtering power was varied from 75 to 150 W, while the deposition time was adjusted to maintain an approximately constant thickness of ~110 nm. The films were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), optical transmittance, and electrical measurements. AFM and SEM analyses revealed an evolution from relatively smooth surfaces at low RF sputtering powers toward increased surface roughness at higher powers. XRD confirmed polycrystalline NiO_x with a face-centered cubic structure, showing a preferential orientation shift from (111) to (200) and a maximum crystallite size of 14.73 nm at 125 W. Electrical resistivity showed a non-monotonic dependence on RF sputtering power, ranging from 25.39 to 309.85 kΩ·cm, indicating that the electrical response cannot be explained solely by crystallite size. Thickness-dependent analysis revealed an evolution from early-stage nucleation toward more developed columnar growth. Finally, comparison with dip-coating and AACVD revealed distinct structure–property relationships among the deposition routes. Full article

Gold-to-gold (Au–Au) bonding forms an oxide-resistant metallic interface without solder or conductive adhesive, making it attractive for heterogeneous integration, MEMS sealing, optoelectronic packaging, and flexible hybrid electronics (FHEs). This review focuses on low-temperature and room-temperature surface-activated Au–Au direct bonding and emphasizes the roles of surface roughness and activation state. Compared with thermocompression bonding (TCB), low-temperature and room-temperature bonding impose stricter surface requirements because heat and pressure in TCB can deform asperities and increase real contact area. Room-temperature bonding instead depends strongly on the surface condition before contact. Successful bonding generally requires very smooth Au surfaces, activation, and contamination control. Reported roughness ranges from below 0.5 nm for smooth sputtered or transferred Au films to tens or hundreds of nanometers for rough plated Au before smoothing. Smoothing strategies can therefore expand the direct-bonding process window. Plasma activation removes contaminants and increases surface reactivity; Ar plasma promotes strong bonding, whereas O₂ plasma can form Au oxide and weaken the interface. Water-vapor plasma-assisted bonding (WVPAB) further enables bonding on rougher electrodes and flexible polymer substrates. Applications include optoelectronic integration, MEMS hermetic packaging, heterogeneous integration, and FHE. Remaining challenges include wafer-scale roughness control, activated-surface lifetime, patterned Au bonding, long-term reliability, and mechanism-based process optimization. Full article

TiN/CrN multilayer coatings with bilayer periods of 20 and 30 nm and TiN:CrN layer thickness ratios of 1:1, 1:2 and 2:1 were deposited on 40Kh steel substrates by pulsed direct current magnetron sputtering (pDCMS). The phase composition (XRD), microstructure (SEM), mechanical (nanoindentation, scratch testing), tribological (dry sliding and boundary lubrication), and corrosion (potentiodynamic polarization in 3.5 wt.% NaCl) characteristics of the coatings were examined. Increasing the TiN volume fraction increased nanohardness and elastic modulus reaching a maximum H³/E² = 0.186 GPa. The Λ30-TiN(20)/CrN(10) coating showed the best adhesion (L_c1 = 14.4 N, L_c2 = 17.7 N, CPR_S = 48 N²) and the lowest wear rate both under dry sliding and under boundary lubrication (1.2 × 10⁻⁵ mm³/(N·m)). In contrast, CrN dominance (Λ30-TiN(10)/CrN(20)) sharply degraded the tribological behaviour (the wear rate increased by almost an order of magnitude) and caused catastrophic localized pitting in the corrosion tests. At the same time, the best corrosion resistance (E_corr ≈ −0.47 V, the most extended quasi-passive region) was achieved at the smallest bilayer period. A balanced composition, Λ20-TiN(10)/CrN(10), owing to the highest density of interlayer boundaries, effectively blocks through-thickness growth defects. The architectures that are optimal in terms of mechanical/tribological and of corrosion criteria do not coincide, which indicates that the TiN:CrN ratio has to be chosen according to the dominant type of service loading. The results obtained show that varying the thickness ratio of the TiN and CrN layers at bilayer periods of 20 and 30 nm makes it possible to tune the balance of hardness, wear resistance, adhesion and corrosion resistance of multilayer coatings on structural steels. Full article

Strontium titanate (SrTiO₃) is a stable, non-toxic perovskite oxide that has attracted interest for photovoltaic and optoelectronic applications, including third-generation photovoltaic devices. However, the production of ceramic targets with suitable density and microstructure for sputtering deposition remains a technological challenge. This study investigates a processing route for SrTiO₃ ceramic targets and their application in thin-film heterostructures. SrTiO₃ powders were synthesized by the Pechini method and densified by Spark Plasma Sintering (SPS), followed by deposition by RF Magnetron Sputtering of thin films. Structural and morphological analyses confirmed the formation of predominantly cubic SrTiO₃ and the densified microstructure of the ceramic target. The optical band gap of the films, determined using the Tauc method for an indirect transition, was 3.42 eV for the as-deposited film and 3.35 eV after annealing. The resulting FTO/SrTiO₃/CdTe/CdCl₂/Au heterostructure exhibited a measurable photoelectric response, with localized photovoltage reaching approximately 400 mV, and photovoltaic parameters of Jsc = 4.32 μA/cm², Voc = 9.75 mV, and FF = 21.4%. These findings demonstrate the feasibility of the proposed processing route for producing SrTiO₃ thin films and their integration into photoactive heterostructures. Full article

TiO₂ nanotubes and ZnO thin films were investigated as oxide-based memristive systems for resistive switching and state-endurance applications under variable environmental conditions. TiO₂ nanotubes were synthesized by electrochemical anodization, while ZnO thin films were deposited on Ti substrates by DC magnetron sputtering. Structural, chemical, and morphological properties were examined by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. TiO₂ exhibited a vertically aligned nanotubular morphology, whereas ZnO showed a granular thin-film surface. Electrical characterization was performed using Au top electrodes and Ti as the bottom electrode under atmospheric pressure and high-vacuum conditions, with temperature varied from 353 K down to 77 K. Both materials exhibited hysteretic current–voltage behavior associated with resistive switching, although their response was strongly influenced by morphology, defect distribution, and environmental conditions. TiO₂ nanotubes showed stable high- and low-resistance states, with an ON/OFF ratio of approximately 4.65, indicating robust state endurance. The observed behavior was attributed to oxygen-vacancy-mediated transport, filament stabilization, and interface effects. These results highlight the relevance of comparing TiO₂ and ZnO nanostructures for identifying oxide systems capable of maintaining resistive states under temperature and pressure variations, supporting their potential for low-power non-volatile memory applications. Full article

In this work, TiO₂ and TiO₂:Co nanotubes were fabricated via electrochemical anodization, using Ti (99.99% purity) and Ti/Co foils as the anode and cathode. Cobalt was deposited onto the Ti foils using the DC magnetron sputtering technique under a working pressure of 2.5 × 10⁻² Torr. The resulting nanotubes exhibited wall nodes and an average length of 308.6 ± 13.07 nm for TiO₂ and 92.63 ± 2.846 nm for TiO₂:Co. The synthesized structures were characterized by X-ray diffraction (XRD), identifying anatase as the predominant phase, accompanied by an amorphous halo. Two types of MSM devices were fabricated to study bulk and surface conduction: a transverse configuration (TE/(TiO₂, TiO₂:Co)/Ti), with top electrodes (TE) of Al or Au, and a coplanar configuration (Al/TiO₂/Al). Surface topography and surface-potential variations were investigated using Atomic Force Microscopy (AFM) and Kelvin Probe Force Microscopy (KPFM), respectively. The device behavior is mainly governed by the TE/TiO₂ junction due to the absence of an energy barrier at the TiO₂/Ti interface. All samples exhibit asymmetric I–V behavior with higher conduction under positive bias. The Au/TiO₂/Ti device showed the lowest resistance among the Ti BE structures, displaying Schottky behavior with low reverse current leakage and a shift in the zero-current crossing depending on the scan direction. Barrier heights near the zero-current crossing, calculated via the thermionic emission model, were 0.91 eV and 0.70 eV for the reverse and forward directions, respectively. Ideality factors and series resistance exceeded 6.8 and 40 kΩ, respectively, suggesting additional transport mechanisms. In addition, magnetization as a function of the applied field was generated in the TiO₂:Co nanotubes, evidencing their ferromagnetic-like behavior. Full article

Stable electrical contacts must maintain mechanical integrity and low electrical resistance under fretting conditions, but the influence of deposition-induced residual stress on coated rough interfaces remains unclear. In this paper, 2.8 μm AgNi coatings containing 1–8 at.% Ni were deposited by magnetron sputtering. Their microstructure, mechanical properties, residual stress, resistivity, and coupled force–resistance responses were examined over 20 displacement-controlled radial-fretting cycles to resolve the early-cycle evolution from initial asperity accommodation to electromechanical stabilization. A residual-stress-aware multiasperity model was developed to interpret the stabilized high- and low-load electrical responses by coupling elastic–plastic asperity contact with finite-thickness constriction resistance and conducting-spot interactions. Increasing Ni content increased the magnitude of the compressive residual stress from 35.3 to 312.3 MPa. The stabilized R_min increased from 0.464 ± 0.028 to 0.575 ± 0.029 mΩ, whereas R_max decreased from 3.064 ± 0.151 to 1.797 ± 0.083 mΩ across the composition series. The cycle-resolved histories showed that R_min was weakly cycle-dependent, whereas R_max increased markedly in the low-Ni coatings as the return-point preload progressively relaxed. At the stabilized cycle, the multiasperity model reproduced the contrasting composition-dependent resistance trends at the high- and low-load endpoints. A paired sensitivity analysis showed that residual stress had a minor influence on R_min but reduced R_max by up to 20.3% by suppressing accumulated plastic settlement and preserving the return-point conducting network. These results reveal a mechanical–electrical design trade-off in which Ni enrichment increases high-load resistance but is associated with improved preload retention and early cycle-to-cycle electrical stability. Full article

Maintaining low leakage current with high capacitance density in metal–insulator–metal (MIM) capacitors is essential for next-generation dynamic random-access memory (DRAM) scaling. Rutile TiO₂ is a promising high-k dielectric; however, its narrow bandgap causes high leakage, while defect-free stabilization in ultrathin films remains challenging. RuO₂/TiO₂/Ru MIM capacitors were fabricated using a reactive direct current (DC)-sputtered RuO₂ bottom electrode, followed by TiO₂ growth by direct plasma atomic layer deposition (DP-ALD) or remote plasma atomic layer deposition (RP-ALD) and rapid thermal annealing in O₂ to reduce defects. Rutile TiO₂ was deposited directly on highly crystalline RuO₂ under both plasma modes, suggesting that RuO₂ crystallinity governs TiO₂ phase evolution. The RP-ALD film replicated the RuO₂ grain morphology, yielding higher roughness than that of the DP-ALD film. Moreover, the RP-ALD film exhibited lower oxygen-vacancy density and improved stoichiometric stability. The RP-ALD-fabricated capacitors exhibited a higher dielectric constant and lower leakage current density at 0.8 V than the DP-ALD-fabricated capacitors (~100 and ~1.76 × 10⁻⁶ A/cm² vs. ~97 and ~1.41 × 10⁻⁴ A/cm², respectively). Ion bombardment during DP-ALD likely promoted oxygen-vacancy-related defect formation, whereas RP-ALD mitigated such damage, improving leakage characteristics. This work highlights the potential of RP-ALD-based RuO₂/TiO₂/Ru MIM capacitors for next-generation DRAM. Full article