Search

ZnO thin films are synthesized by an ultrasonic spray pyrolysis method, with the deposition temperature in a range between 250–450 °C. The obtained thin films are analyzed by X‐ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL). The samples are used in a photocatalytic experiment to compare the degradation efficiency by methylene blue decomposition under UV irradiation. XRD patterns confirm a polycristalline wurtzite structure with preferred orientation along the (002) plane. AFM images reveal an important change in the shape and size of the grains constituting the surface. The roughness values are in the range of 17–93 nm. Thickness values of thin films deposited at 250, 350, and 450 °C are ≈0.9, 2.3, and 1.4 µ, respectively. From PL characterization, the spectra are found to be sensitive to the deposition temperature, where emission peaks with different forms and intensities are observed. One peak at 389 nm is attributed to the recombination of free excitons, and other peaks between 403–522 nm correspond to violet, blue, and green emissions indicating the presence of Zn vacancies, Zn interstitials, and oxygen vacancies, respectively, in the ZnO structure. The photocatlytic results show that the best photocatalytic efficiency of 88% is achieved by ZnO thin film deposited at 450 °C. [ABSTRACT FROM AUTHOR]

Zirconium nitride films are deposited onto stainless steel AISI 316L and silicon (100) by radio frequency magnetron sputtering at different nitrogen flow ratios [N2/(Ar+N2)] varied between 0 and 0.25). Scanning electron microscope, atomic force microscopy, X‐ray diffraction (XRD), and Raman are used to investigate the surface morphology and microstructure of the thin films. The mechanical and electrochemical properties of all coatings are evaluated and compared with the uncoated AISI 316L to explore the efficiency of surface modification. The XRD and Raman analysis show that all the films are crystalline. This shows that the increased nitrogen content leads to a transformation from hexagonal α‐Zr phase to cubic c‐Zr and then to mixed α‐Zr and face centered cubic c‐ZrN phases. The films deposited with nitrogen flow ratio of 0.2 show the highest hardness of 32.2 GPa. Using the potentiodynamic polarization method, the corrosion behavior of the films is studied in Hank's solution. The comparison between uncoated and coated substrates shows a decrease in corrosion current density for all coated samples. [ABSTRACT FROM AUTHOR]

In order to study the influence of the substrate bias on the properties of ZrN thin films deposited by radio-frequency magnetron sputtering for biomedical application. Films of ZrN were grown onto 316L stainless steel substrate using radio-frequency (rf) magnetron sputtering from a pure zirconium target in Ar - N2 gas mixture. The substrate bias voltage was varied from 0 to −100 V, which produces a variation in the structural and electrochemical properties of the obtained films. The deposited films were characterized by X-Rays Diffraction, Atomic Force Microscopy, scanning force microscopy and potentiodynamic polarization. [ABSTRACT FROM AUTHOR]

ZrO2 thin films were deposited on 316L stainless steel substrate by a radio-frequency magnetron sputtering system. The substrate bias voltage, the working gas rate and the reactive gas fraction in the gas mixture were varied. These variations produce a variation in the deferent properties of the obtained films. The deposited films were characterized by X-Rays Diffraction, Atomic Force Microscopy, nano-indentation and potentiodynamic polarization. The experimental results show that the film thickness and the roughness of the films are highly influenced by the plasma parameters. XRD results show that the monoclinic phase is predominant in unbiased deposited films. The best anti-corrosion performance and hardness were obtained for ZrO2 deposited with a substrate bias voltage of −75 V, Ar rate of 6 sccm and oxygen fraction of 25%. [ABSTRACT FROM AUTHOR]

In this study, a negative substrate bias voltage is used to tune the structural, morphological, mechanical and electrochemical properties of TiAlN coatings fundamental for protective coating applications. TiAlN thin films have been deposited on glass, (001)Si and stainless steel substrates by RF magnetron sputtering at a power density of 4.41 W/cm2. The deposition rate was determined from X-ray reflectivity measurements to 7.00 ± 0.05 nm/min. TiAlN films used in this work were deposited for 60 min to yield a film thickness of 420 nm. Structural analysis has shown that TiAlN coating forms a cubic (fcc) phase with orientations in (111), (200), (220) and (222) planes. The deposited coatings present maximum hardness (H = 37.9 GPa) at −75 V. The dependence of hardness and Young's modulus and corrosion resistance on microstructure has been established. Electrochemical studies by potentiodynamic polarization in aggressive environment (3.5 wt.% NaCl) have revealed that stainless steel substrate with TiAlN coating exhibits excellent corrosion resistance. [ABSTRACT FROM AUTHOR]

Titanium oxide (TiO2) films have been synthesized on quartz, silicon and textured silicon substrates by chemical ultrasonic spray deposition. The textured silicon substrate was carried out using Na2CO3 solution. The sample surface exhibits uniform pyramids with an average height of 5 µm. In this paper, particular attention is given to the TiO2 films prepared by spray ultrasonic system using Tetra iso-Propoxide Orthotitanate Titanium (TPOT) as a precursor. The solutions were sprayed onto substrates heated at various temperatures 350 - 550 °C. The properties of films as a function of temperature parameter were investigated using structural and optical analysis. According to XRD, FTIR and Micro-Raman spectroscopies, the anatase phase was found and exhibits nanograins of 9 to 15 nm in size. The indirect and direct bad gap were found to increase by increasing substrate temperature due to the decreasing of nanograins size and were estimated to be around 3.28 and 3.38 eV. A transmittance higher than 80% was found. This paper reports on anti-reflection coating application of TiO2 layers due to its good transparency and appropriate refractive index varies between 2.19 - 2.40 at λ = 632.8 nm as a function of temperature determined by UVVisNIR spectrophotometer and Ellipsometry. To achieve optimum anti-reflection characteristics different anti-reflection designs were experimentally examined with polished and textured substrates. The average reflectance of the polished silicon used in this study is 39%, with TiO2 it decreases to 9%. The textured surface reduces the average reflectance of silicon to be around 14% and it decreases dramatically to 5% after deposition of a single layer of TiO2 as an anti-reflection coating. The gain in density of the short-circuit photocurrent assigned to the reduction of reflection losses up to 44% and 58% were predicted with TiO2 single-coating in polished and textured silicon substrates respectively. [ABSTRACT FROM AUTHOR]

In this paper, we report an experimental evidence of the impact of applied a low magnetic field ( B<10~mT ) during negative bias temperature instability (NBTI) stress and recovery, on commercial power double diffused MOS transistor. We show that both interface (\Delta Nit) and oxide trap (\Delta Not) induced by NBTI stress are reduced by applying the magnetic field. This reducing is more pronounced as the magnetic field is high. However, the dynamic of interface trap during stress and recovery phase is not affected by the applied magnetic field. While, the dynamic of oxide trap is affected in both stress and recovery phases. [ABSTRACT FROM PUBLISHER]

The aim of this study is to investigate the influence of plasma deposition parameters (the pressure and the substrate bias voltage Vs) on structure, surface morphology, hardness and electrochemical behavior (studied by potentiodynamic polarization and optical microscope (OM) in aggressive environment NaCl 3.5 wt%) of TiAlN coatings. The coatings were deposited by reactive RF magnetron sputtering (13.56 MHz). They were carried out during 60 min and their thickness was approximately 1 μm. Structural analysis shown that TiAlN coating crystallized in cubic (fcc) and hexagonal (hcp) structure with orientations in (1 0 0), (1 1 1), (2 0 0), (1 1 0), (2 2 0) and (3 1 1) planes. The deposited coatings present maximum hardness ( H = 25.75 GPa) and Young's modulus ( E = 479.82 GPa) at low pressure (20 mTorr) and −60 V of negative substrate bias. Also, mechanical properties ( H & E ) were strongly influenced by coatings density and grain size. Electrochemical tests revealed that XC48 steel substrate covered with TiAlN coating exhibits excellent corrosion resistance. [ABSTRACT FROM AUTHOR]

• ZrO 2 films were deposited on stainless steel 316L by RF magnetron sputtering. • The ZrO 2 coated 316L are hydrophobic. • Bioactivity tests in vitro demonstrate the formation of a hydroxyapatite layer on the films surface. The zirconia (ZrO 2) films were deposited using radio-frequency magnetron sputtering (RFMS) from a pure zirconium target in Ar-O 2 gas mixture with different percentage of the oxygen. The effect of Oxygen percentage on the film's characteristics was investigated by Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and tribology test. Also, the contact angle of the films was measured in order to evaluate their hydrophobicity. Additionally, in vitro test in artificial blood plasma and further SEM observations were performed to study bioactivity of the films. The experimental results showed that the roughness, the porosity and the thickness of the films depend on the oxygen percentage. According to XRD and Raman spectroscopy results, the films present a polymorph phase of monoclinic and tetragonal. Zirconia films at low oxygen percentage showed better hydrophobic behavior with 114.5° at 15% of oxygen. These films also exhibit a lower friction coefficient and wear rate (0.22 and 6 × 10−07 mm3/m respectively). However the best bioactive behavior was exhibited by the films deposited at 25% of oxygen due to their higher roughness and porosity. In fact, it was found that the bioactivity of the films is highly dependent on the porosity and roughness of the films. [ABSTRACT FROM AUTHOR]

In this work, TiO2 layers are synthetized on Ti6Al4V alloy substrate by electrochemical anodizing process in fluoride‐containing alkaline electrolytes and under different applied voltages (10, 20, and 30 V). The scanning electron microscopy (SEM) reveals a nearly regular and vertical alignment of TiO2 nanotubes (≈80–100 nm) for specimen treated at 20 V and an agglomerate of particles with no particular orientations for those specimens treated at 10 and 30 V. The X‐ray diffraction (XRD) indicates the formation of mixed phases of anatase and rutile. Wettability measurements exhibit hydrophilic and superhydrophilic surfaces, according to the anodization parameters. The electrochemical impedance spectroscopy (EIS), performed in a simulated body fluid (Hank's solution), reveals an increase in corrosion resistance for a bias potential of 20 V (262 kΩ) owing to the evolution in TiO2‐layer thickness, and then decreases for higher anodizing potential values due to the chemical dissolution of the obtained layer. TiO2 nanostructured layers for biomedical application are synthesized on Ti6Al4V substrate by electrochemical anodizing process in fluoride‐containing alkaline electrolyte under different applied voltages. The effects of anodizing parameters on the morphology, crystal phases, and the surface wettability are investigated. The electrochemical test in a simulated body fluid (Hank's solution) indicates the best corrosion resistance for specimen anodized at 20 V. [ABSTRACT FROM AUTHOR]