Effects of post-deposition annealing on the structure and optical properties of Y2O3 thin films

Y₂O₃ thin film waveguides were prepared by RF magnetron sputtering. The effects of post-deposition annealing on the structure and optical properties have been investigated. The structural evolution of Y₂O₃ films with annealing temperature was investigated by X-ray diffraction (XRD). Spectroscopic ellipsometry was employed to determine the optical properties of Y₂O₃ films annealed at various temperatures. It was found that with increasing annealing temperature, the refractive index (n) of Y₂O₃ films increases. The optical band gap of Y₂O₃ films shifts to higher energy after higher temperature annealing, which is likely due to the reduction of defects and the change of crystalline structure in Y₂O₃ films.     

Fabrication of YbAl3 film via annealing amorphous Yb-Al film deposited by RF magnetron sputtering

YbAl₃ single-phase bulk alloy was synthesized by melting at 1258 K using raw Yb and Al metals in the ratio of 1:2.2. A sputtering YbAl₃ target was prepared using the precursor YbAl₃ bulk alloy with the spark plasma sintering process. An amorphous Yb-Al film was fabricated by RF magnetron sputtering using the YbAl₃ target, and a single-phase crystalline YbAl₃ film was fabricated by annealing the amorphous Yb-Al film at temperatures higher than 923 K in Ar atmosphere.     

Structure, conductivity, and optical absorption of Ag2−xO films

Evaporation of Ag in the presence of an electron cyclotron resonance (ECR) oxygen plasma was used to deposit Ag_2−xO films with a range of stoichiometries onto r-plane sapphire substrates. A quartz crystal oscillator (QCO) was used to accurately measure the silver and oxygen arrival rates and establish the O/Ag flux ratio needed to produce films with nominal Ag₂O stoichiometry. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis indicates that the Ag_2−xO films are not single phase but contain signatures of coexisting Ag₂O and AgO components. XRD shows that the lattice matching with the r-plane sapphire substrate causes the Ag₂O phase to grow with <002> heteroepitaxial crystallites coexisting with crystallites having <111> normal and random in-plane orientation. The AgO phase also forms with crystallites having <002> heteroepitaxy as well as crystallites with <111> normal and random in-plane orientation. The mixed phase Ag_2−xO films exhibit approximately 77% optical transmission over the visible range (500 nm to 700 nm) and have a single absorption edge near 3.3 eV. Four-point van der Pauw conductivity and Hall effect measurements indicate that the Ag_2−xO films are p-type with a conductivity on the order of 3 × 10^− 3 Ω^− 1 cm^− 1.     

Effect of sputtering pressure and post-annealing on hydrophilicity of TiO2 thin films deposited by reactive magnetron sputtering

A series of TiO₂ thin films was deposited onto glass substrates without intentional heating or biasing by magnetron sputtering of a titanium target using Ar/O₂ reactive mixtures over a broad range of total sputtering pressures from 0.12 Pa to 2.24 Pa. Each of the film types was deposited by the threshold poisoned mode at a specific given oxygen flow rate monitored in-situ by optical emission spectroscopy. Both the sputtering pressure and thermal annealing are the key factors for the TiO₂ films to yield fast-response superhydrophilicity with a water contact angle of 5°. The mechanism of superhydrophilicity for the TiO₂ films deposited by high-pressure sputtering will be discussed based on empirical studies of X-ray diffractometry, high-resolution scanning microscopy and atomic force spectroscopy.     

Effects of process parameters on the LaNiO3 thin films deposited by radio-frequency magnetron sputtering

LaNiO₃ thin films were deposited by radio-frequency magnetron sputtering on both (100) Si and platinized Si substrates. The effects of relative oxygen ratio, substrate and annealing temperatures on the microstructure and the electrical properties of the films were investigated. The La/Ni ratio was found to be influenced by the relative oxygen ratio. On the other hand, the orientation of LaNiO₃ was significantly influenced by the substrate temperature. Highly (100)-oriented LaNiO₃ thin films were obtained on SiO₂/Si(100) and Pt/Ti/SiO₂/Si substrates when the substrates temperature was 300 °C with the relative oxygen ratio below 33%. In addition, the (100)-oriented LaNiO₃ showed the lower resistivity than that of random-oriented LaNiO₃.     

Effect of substrate temperature on the structure and optical properties of ZnO thin films deposited by reactive rf magnetron sputtering

Zinc Oxide films were deposited on quartz substrates by reactive rf magnetron sputtering of zinc target. The effect of substrate temperature on the crystallinity and band edge luminescence has been studied. The films deposited at 300 °C exhibited the strongest c-axis orientation. AFM and Raman studies indicated that the films deposited at 600 °C possess better overall crystallinity with reduction of optically active defects, leading to strong and narrow PL emission.     

Microstructure and mechanical properties of TiAlN/SiO2 nanomultilayers synthesized by reactive magnetron sputtering

TiAlN/SiO₂ nanomultilayers with different SiO₂ layer thickness were synthesized by reactive magnetron sputtering. The microstructure and mechanical properties were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nano-indentation. The results indicated that, under the template effect of B1-NaCl structural TiAlN layers, amorphous SiO₂ was forced to crystallize and grew epitaxially with TiAlN layers when SiO₂ layer thickness was below 0.6 nm, resulting in the enhancement of hardness and elastic modulus. The maximum hardness and elastic modulus could respectively reach 37 GPa and 393 GPa when SiO₂ layer thickness was 0.6 nm. As SiO₂ layer thickness further increased, SiO₂ transformed back into amorphous state and broken the coherent growth of nanomultilayers, leading to the decrease of hardness and elastic modulus.     

Photo-fixation of SO2 in nanocrystalline TiO2 films prepared by reactive DC magnetron sputtering

We report on photo-fixation of SO₂ onto nanostructured TiO₂ thin films prepared by reactive DC magnetron sputtering. The films were exposed to 50 ppm SO₂ gas mixed in synthetic air and illuminated with UV light at 298 and 473 K. The evolution of the adsorbed SO_x species was monitored by in situ Fourier transform infrared specular reflection spectroscopy. Significant photo-fixation occurred only in the presence of UV illumination. The SO₂ uptake was dramatically enhanced at elevated temperatures and then produced strongly bonded surface-coordinated SO_x complexes. The total SO_x uptake is consistent with Langmuir adsorption kinetics. The sulfur doping at saturation was estimated from X-ray photoelectron spectroscopy to be ~ 2.2 at.% at 473 K. These films were pale yellowish and had an optical absorption coefficient being ~ 3 times higher than in undoped film. The S-doped films exhibit interesting oleophobic properties, exemplified by the poor adherence of stearic acid. Our results suggest a new method for sulfur doping of TiO₂ to achieve combined anti-grease and photocatalytic properties.     

Effect of annealing on the electrodeposited Cu2O films for photoelectrochemical hydrogen generation

Cu₂O films were electrodeposited on stainless steel substrates followed by Ar annealing for photoelectrochemical hydrogen generation. Plating variables including time and pH for the plating bath were explored to obtain desirable film qualities. X-ray diffraction (XRD) patterns indicated that the as-deposited Cu₂O films exhibited preferred orientations in (200) and (111) planes from the plating bath of pH 9 and pH 11, respectively. Images from scanning electron microscope (SEM) revealed pyramid-like grains in 1 µm size for the Cu₂O films from pH 9 plating bath and large plate-like grains in 3-8 µm size from pH 11 plating bath. Identical results from SEM and XRD were obtained from the Cu₂O films at longer plating time. After annealing at 350 °C for 30 and 60 min, the Cu₂O phase was nicely maintained but SEM images demonstrated coarser grains. Photoelectrochemical activity for H₂ generation was obtained on the Cu₂O films before and after annealing by recording relevant photoelectrochemical currents at − 0.3 V in 0.5 M aqueous Na₂SO₄ solution. For the Cu₂O films from both baths, substantial increments in photoelectrochemical current were observed for the annealed samples as opposed to as-deposited ones. The largest photoelectrochemical current was obtained at 0.143 mA/cm² from the Cu₂O film of pH 9 plating bath with 60 min annealing, which exhibited a 560% increase over the as-deposited sample. We attributed the enhanced photoelectrochemical current to the improved crystallinity and reduced defects for the annealed Cu₂O films.     

Optoelectronic properties of sputter-deposited Cu2O-Ag-Cu2O treated with rapid thermal annealing

Cu₂O and two types of Cu₂O-Ag-Cu₂O (CAC) multilayered thin films were deposited on glass substrates using DC-magnetron sputtering. For CAC films, the mass thickness of Ag layer was controlled at 3 nm. After deposition, some of these films were annealed using a rapid thermal annealing (RTA) system at 650 °C, in order to create embedded Ag particles. AC films were used to study the clustering effect of Ag in Ar atmosphere, as well as for forming the 2nd type of CAC film by covering another Cu₂O layer on the annealed AC structure. A UV-VIS-NIR photometer, a Hall measurement system, and a I-V measurement system were used to characterize the optical and electrical properties of these films with and without RTA. The results show that 2-dimensional Ag layer can transform into many individual particles due to its high surface tension at annealing temperature, no matter when the annealing was carried out. For CAC films, without annealing, the optical transmission and the resistivity are decreased with the inserted Ag layer. After annealing, both the transmission and resistivity are increased, possibly due to the clustering effect of Ag layer. Most importantly, it is found that the embedded Ag particles can increase the light absorption in the NIR-IR region, which can increase photo-induced current.     

Tribological properties of WS2 composite film prepared by a two-step method

In order to extend the application range of solid lubricant WS₂, the author adopted a two-step method to prepare WS₂ film; namely, W film was first fabricated on the AISI 1045 steel by magnetron sputtering method, and then treated by low temperature ion sulfuration to obtain WS₂ composite film. XRD was used to analyze the phase structure of the WS₂ composite film; its surface and worn scar morphologies were analyzed with SEM + EDS; X-ray stress determinator was utilized to measure its residual stress; the nano-hardness and elastic modulus of WS₂ composite film were surveyed by a nano-indentation tester. The tribological properties were investigated on a ball-on-disk wear tester under dry condition. The results showed that WS₂ composite film had much better anti-friction and wear-resistance properties than the original 1045 steel and sulfurized layer.     

Microstructure and tribological behavior of WS2-Ag composite films deposited by RF magnetron sputtering

WS₂-Ag composite films were deposited on medium carbon steel substrate by RF magnetron sputtering method. The morphology and microstructure of the composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tribological behavior was investigated using a ball-on-disk tribometer in vacuum and in humid air. In the range of Ag content of the film from 4.2 at.% to 40.4 at.%, Ag phase dispersed in amorphous WS₂ matrix, and it changed from amorphous to crystalline structure with the increase of Ag content. The friction coefficients of composite films in humid air were lower and more stable than those of pure WS₂ film, and the environmental sensitivity of tribological behavior decreased obviously with the addition of Ag in the films. At the content of 16.2 at.% Ag, the composite film was dense and adherent, and exhibited excellent tribological performance both in vacuum and in humid air.     

Microstructures of ITO films deposited by d.c. magnetron sputtering with H2O introduction

ITO films were deposited by d.c. magnetron sputtering with/without H₂O introduction. The structural and optoelectrical properties of the films were analyzed in detail. The films deposited with H₂O introduction exhibited an entirely amorphous structure, whereas the as-deposited films deposited without H₂O introduction exhibited a polycrystalline In₂O₃ structure. The amorphous ITO films deposited under the high H₂O partial pressure were confirmed to contain a much higher concentration of hydrogen inside the films by secondary ion mass spectroscopy, which remained after post-annealing at 350 °C. The crystallization temperature of the films subjected to post-annealing was increased to higher than 220 °C. These stable amorphous ITO films had a wet-etching rate in oxalic acid solution two orders of magnitude higher than that of the films deposited without H₂O introduction.     

Preparation of amorphous FexSi(1 − x) film using unbalanced magnetron sputtering

The preparation of iron-silicon films was performed onto Si (100) substrates by microwave electron cyclotron resonance (ECR) plasma source enhanced unbalance magnetron sputtering. The compositions, microstructures and properties of films under different sputtering powers and annealing conditions were characterized by AES, GAXRD, TEM and absorption spectrum techniques. The results described that the amorphous iron silicon films can be easily prepared by unbalance magnetron sputtering. Even the Fe/Si ratio deviated far from 1:2, such as Fe/Si = 1:14.8 or 1:10, the amorphous iron silicon film with semiconductor properties can also be obtained, which suggests that the Fe/Si ratio is not the only factor to determine whether the samples have semiconducting properties in iron silicon amorphous. After annealing at 850 °C for 4 h, the microstructure of nanometer β-FeSi₂ embedded into amorphous Si still possesses semiconducting characteristics.     

Control of the optical properties of silicon and chromium mixed oxides deposited by reactive magnetron sputtering

The development of mixed-oxide thin films allows obtaining materials with better properties than those of the different binary oxides, which makes them suitable for a great number of applications in different fields, such as tribology, optics or microelectronics. In this paper we investigate the deposition of mixed chromium and silicon oxides deposited by reactive magnetron sputtering with a view to use them as optical coatings with an adjustable refractive index. These films have been characterized by means of Rutherford backscattering spectrometry, Auger electron spectroscopy, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy and spectroscopic ellipsometry so as to determine how the deposition conditions influence the characteristics of the material. We have found that the deposition parameter whose influence determines the properties of the films to a greater extent is the amount of oxygen in the reactive sputtering gas.     

Photocatalytic TiO2 films deposited on cenosphere particles by pulse magnetron sputtering method

In the present study, TiO₂ films were deposited on the surface of cenosphere particles using the modified magnetron sputtering equipment under different working conditions. The resulting films were characterized by field emission scanning electron microscopy (FE-SEM), Atomic Force Microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The FE-SEM and AFM results show that the grain sizes and root-mean-square (RMS) roughness values of the TiO₂ films increase with the increase in deposition time and film thickness. The XRD results indicate that the film was TiO₂ film and sputtering time is an importance condition to influence the films crystal. With the increasing of sputtering time, the crystallization of the TiO₂ film was increased. The XPS results show that only TiO₂ films existed on the surface of cenosphere particles. In addition, the photocatalytic activities of these films were investigated by degrading methyl orange under UV irradiation. The results suggest that the photocatalytic activity of cenosphere particles with anatase TiO₂ films is remarkable and this catalyst can be applicable for the photocatalytic degradation of other organic compounds under UV lights.     

Influence of N2 partial pressure on mechanical properties of (Ti,Al)N films deposited by reactive magnetron sputtering

The influence of the nitrogen partial pressure on the mechanical properties of (Ti,Al)N films deposited by DC reactive magnetron sputtering using a Ti-Al mosaic target at a substrate bias of −100 V is investigated. Nanoindentation tests reveal that with increasing N₂ partial pressure, the film hardness and elastic modulus increase initially and then decrease afterwards. The maximum hardness and elastic modulus are 43.4 GPa and 430.8 GPa, respectively. The trend is believed to stem from the variations in the grain size and preferential orientation of the crystals in the (Ti,Al)N films fabricated at varying N₂ partial pressure. The phenomenon is confirmed by results acquired using glancing angle X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS).     

Characterization of SiO2 and TiO2 films prepared using rf magnetron sputtering and their application to anti-reflection coating

Preparation of TiO₂ and SiO₂ films for optical applications was attempted using conventional rf magnetron sputtering in the sputtering ambient with various O₂/Ar+O₂ ratios and at substrate temperatures between room temperature and 400 °C. X-ray photoelectron spectroscopy (XPS) and optical spectroscopy investigations indicated that oxygen addition in the sputtering ambient was essential for growing TiO₂ films with stoichiometric compositions and good transmittance, while SiO₂ films had a stoichiometric composition of O/Si ratio=2.1-2.2 and were highly transparent in the visible wavelength region, independent of gas composition in the growing ambient. It was also identified from scanning electron microscope (SEM), atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FTIR) measurements that the structural characteristics of both TiO₂ and SiO₂ films were significantly improved with O₂ addition in the sputtering ambient, showing smoother surface morphologies and higher resistances to water absorption when compared with films grown without O₂ addition. Heating of the substrate between 200 and 400 °C considerably increased the refractive index of TiO₂ layers, resulting in dense structures along with an improvement of crystallinity. For optical applications, AR coatings composed of 2-4 multi-layers on glass were designed and manufactured by stacking in turn the SiO₂ and TiO₂ films at room temperature and O₂/Ar+O₂=10%, and the performance of the produced coatings was compared with simulation results.     

Photocatalytic Zn-doped TiO2 films prepared by DC reactive magnetron sputtering

Zn-doped TiO₂ films were prepared by means of pulsed DC reactive magnetron sputtering method using Ti and Zn mixed target. The deposition condition was optimized to produce uniform and transparent TiO₂ films. Titanium was in the Ti⁴⁺ oxidation state in all Zn-doped TiO₂ films. The zinc oxide deposited on the substrate was in the fully oxidized state of ZnO. Increase of zinc concentration inhibited the crystal growth in the TiO₂ films. The surface morphology gradually changed from crystalline to amorphous along with the increase of doped zinc concentration. The optical transmittances of these films decreased only slightly with increasing zinc concentration due to very similar band edges of ZnO and anatase TiO₂. The doped ZnO had weak influence on light absorption of the TiO₂ films. When zinc concentration was very low (<1 at%), the photocatalytic activities of the doped films had nearly no difference from that of pure TiO₂ film. Photocatalytic activities decreased obviously in the films containing high amount of zinc oxide.     

Photocatalytic activity of TiO2 thin films deposited by RF magnetron sputtering

Nano-TiO₂ thin films were deposited on silicon and glass substrates by radio-frequency (RF) magnetron sputtering using TiO₂ ceramic target and characterized by X-ray diffractometer, X-ray photoelectron spectrometer, atomic force microscope, and ultraviolet-visible spectrophotometer. Photocatalytic activity was evaluated by light induced degradation of 5 ppm methyl orange solution using a high pressure mercury lamp as lamp-house. It was found that the film as deposited is polymorph, with energy gap of 3.02 eV, and can absorb visible light. The film was repeatedly used for six times in degradation of 5 ppm methyl orange, and the degradation rates of methyl orange solution are 36.566%, 33.112%, 32.824%, 32.248%, 30.521% and 28.794%, respectively. After ultrasonic treatment in de-ionized water for ten minutes, the degradation rate of methyl orange solution resumes to 33.975%.