Anomalous elastic properties of RF-sputtered amorphous TeO2+x thin film for temperature-stable SAW device applications.

The anomalous elastic properties of TeO2+x thin films deposited by rf diode sputtering on substrates at room temperature have been studied. The deposited films are amorphous, and IR spectroscopy reveals the formation of Te-O bond. X-ray photoelectron spectroscopy confirms the variation in the stoichiometry of TeO2+x film from x=0 to 1 with an increase in the oxygen percentage in processing gas composition. The elastic parameters of the films in comparison to the reported values for TeO2+x single crystal are found to be low. However, the temperature coefficients of elastic parameters of all deposited films exhibit anomalous behavior showing positive values for TC(C11) in the range (32.0 to 600.0)x10(-4) degrees C(-1) and TC(C44)=(35.0 to 645.5)x10(-4) degrees C(-1) against the negative values TC(C11)=-2.7x10(-4) degrees C(-1) and TC(C44)=-0.73x10(-4) degrees C(-1) reported for TeO2+x single crystal. The variation in the elastic parameters and their temperature coefficients is correlated with the change in the three-dimensional network of Te-O bonding. The anomalous elastic properties of the TeO2+x films grown in 100% O2 are useful for potential application in the design of temperature stable surface acoustic wave devices.     

Vapor growth and properties of thin film ZnSxSe1−x

ZnS_xSe_1?x has been heteroepitaxially deposited onto GaAs by hydrogen vapor transport in an open-tube reactor. ZnS_xSe_1?x alloy films over the entire composition range were grown and determined to be monocrystalline. The effects of reactant partial pressure and substrate temperature on alloy composition have been investigated. Capacitance-voltage measurements on Au/ZnS_xSe_1?x Schottky diodes indicated donor densities of the order of (0.7?20) × 10¹⁵cm^?3 in films grown under zinc-rich conditions.     

Electrical transport properties of bulk amorphous Gex Se1−x

d. c. -Conductivity measurements have been made as a function of temperature (80–330 K) on bulk amorphous samples of Ge_xSe_1?x (0.1 ? x ?0.7), in order to identify the conduction mechanism and to observe the effect of selenium -doping on the d. c.-conductivity of germanium. It is found that for samples with a low concentration of selenium (0. 5? x ? 0. 7 ), conduction in the high temperature region (330-180 K) is due to thermally assisted tunneling of electrons in the localized states at the conduction band edge, and in the low temperature region (80–190 K), conduction takes place through variable range hopping in the localized states near the Fermi level. The addition of selenium is found to increase the amorphicity of the samples. In the samples with a relatively high content of selenium (0.1 ? x ? 0.4), conduction in the entire temperature range of investigation is due to the thermally assisted tunneling of holes in the localized states at the valence band edge.     

Optical properties of thin film Au-MgF2 cermets

The preparation of thin films of cermets of gold in magnesium fluoride and the ellipsometric determination of the optical constants of the materials of the films are described. The results for materials of two compositions are compared with predictions based on the Maxwell Garnett expression for the complex refractive index of cermets in terms of the refractive indices of the constituents. It is shown that reasonable agreement between experimentally determined and theoretical values of the refractive indices of the cermets can be approached only if the restriction of the mean free paths of the conduction electrons in the gold particles is taken into account.     

非晶态TiO2-Ag薄膜的光催化性能研究

采用磁控溅射技术在玻璃基片上制备了非晶态的TiO2-Ag薄膜,用XRD、XPS、STS和椭圆偏光测厚仪等对薄膜的晶体结构、表面成分、电子结构和薄膜厚度进行了测试分析.试验和测试结果表明,薄膜呈非晶态,在薄膜表面存在单质Ag,其与Ti的原子浓度比为1.8:1.STS测试得到薄膜的禁带宽度为1.8eV.对10mg/L的亚甲基蓝溶液光催化脱色实验表明,随着薄膜厚度的增加,光催化脱色率递增,当厚度达360nm时,薄膜对亚甲基蓝的脱色率在2h达90%以上,当厚度＞360nm时,光催化脱色率不再增加;对2mg/L罗丹明B溶液光催化脱色实验表明,其脱色率对薄膜厚度的增加不敏感,薄膜对罗丹明B的脱色率在3h内达到88.7%.     

Effect of thermal annealing time on optical and structural properties of TeO2 thin films

TeO₂ thin films were deposited on quartz substrates by rf reactive sputtering technique from a Te metal target. The obtained samples were annealed in an argon atmosphere at 450 °C for different annealing times up to 90 min. X-ray diffraction studies revealed that the as-grown samples were amorphous and there was no appreciable change in structure for a short annealing time. Thin films became polycrystalline with the tetragonal (α-phase) structure of tellurium dioxide crystal with the increase of the thermal annealing time. The refractive index and optical energy gap of the films were calculated by modelling transmittance spectra. The optical energy gap decreased continuously from 3.83 eV to 3.71 eV with increasing thermal annealing time.     

Optical properties of Tm3+-doped TeO2-WO3 glasses

Tm³⁺-doped TeO₂-WO₃ glasses have been prepared and their absorption spectra have been measured in the visible to IR (up to 7 μm) spectral region. Luminescence measurements have shown that the glasses have emission bands at 1.45 and 1.8 μm. An attempt was made to remove OH groups from the glasses using KBF₄ and an inert atmosphere during the glass preparation. The results demonstrate that a low OH content can be achieved only by combining these approaches. The 1.8-μm emission intensity in “dry” glass is a factor of 6 higher than that in the OH-containing glasses. The relevant Judd-Ofelt parameters have been calculated.     

Fabrication of TiO2 thin film memristor device using electrohydrodynamic inkjet printing

In this paper, we are reporting the fabrication of memristor device (Ag/TiO₂/Cu) using electrohydrodynamic inkjet printing technology. The titanium oxide (TiO₂) active layer was deposited using electrohydrodynamic atomization technique. The metal electrodes were patterned by using electrohydrodynamic printing technique. The crystalline nature, surface morphology and optical properties of as deposited TiO₂ films were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and UV-visible spectroscopic analysis respectively. XRD and SEM studies revealed that the presence of anatase TiO₂ with uniform deposition. The optical transmittance of the deposited TiO₂ films was observed to be 87% in the visible region. The fabricated memristor device (Ag/TiO₂/Cu) exhibits bipolar resistive switching behavior within the low operating voltage (± 0.7 V). Our results ensure that the printed technology provides breakthrough solution in the electronic memory device fabrication.     

The effect of oxygen partial pressure on the properties of RF-sputtered Al2O3 thin films

Aluminum oxide thin films are used as insulating and passivating layers in a variety of microelectronic and other applications. RF bias sputtering was used to deposit Al₂O₃ films. The effects of oxygen partial pressure on the deposition rate, argon content, refractive index, etch rate, substrate temperature and uniformity were characterized by alpha-step scan, EDX, AES, XPS, STEM, X-ray diffraction and ellipsometry.     

用于微测辐射热计的氧化钒薄膜的光电性能研究

采用磁控溅射方法在p-Si(100)衬底上制备了VO2和择优取向的V6O13混合相成分的薄膜.利用X射线衍射(XRD)分析、原子力显微镜(AFM)、傅立叶红外光谱(FT-IR)分析及四探针测试方法,研究了薄膜的相成分和红外吸收特性,并测试分析了薄膜的电学热稳定性.研究结果表明,通过这种方法制备的氧化钒薄膜具有较低的电阻率和较高的电阻温度系数(TCR),并且具有良好的热稳定性,可以作为微测辐射热计的热敏材料.     

Thermal stability and crystallization of amorphous Si1−xBx, Si1−xPx and Si1−xSbx alloy thin films

The thermal stability and crystallization of the amorphous Si_1−xP_x, Si_1−xB_x and Si_1−xSb_x alloy systems have been studied by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). It was found that the amorphous Si-P and Si-B alloys have a high thermal stability and crystallize at temperatures as high as 1150°C, whereas amorphous Si-Sb alloys are unstable and crystallize already at 350°C. The thermal stability is explained by strong Si-P and Si-B bonds, whilst the instability is explained by the weakening of Si-Si bonds by the presence of Sb atoms (< 17 at.% Sb) and by weak Si-Sb and Sb-Sb bonds (> 17 at.% Sb). The thermal stability and instability of the amorphous alloys were correctly predicted from calculated Gibbs free energy diagrams (GFED). The calculated GFED were also used together with the observed crystallization temperatures to successfully predict the first crystalline phase to form in the Si-P and Si-B systems. The first crystalline phases that formed were Si (< 40 at.% B and < 30 at.% P), a newly reported phosphide, Si₁₂P₅ (30 at.% P), and SiP (> 30 at.% P).     

Development of smooth CuInGa precursor films for CuIn1 − xGaxSe2 thin film solar cell applications

CuInGa precursor thin films were deposited using a CuGa (75-25 at.%) and an In 3″ diameter target material simultaneously by RF magnetron sputtering. The precursor films were deposited on Si and glass substrates at − 80 °C and room temperature, and characterized by Rutherford backscattering spectroscopy, Auger electron spectroscopy, scanning electron microscopy, atomic force microscopy and X-ray diffraction. The effects of gun power density and substrate temperatures on resulting precursor film properties were investigated. Precursor films deposited at − 80 °C have a smooth morphology with a 75% reduction in all roughness values and are more dense and homogeneous in structure compared to precursors deposited at room temperature. Therefore these precursors will result in better selenization process reproducibility.     

Some experimental results on the magnetic properties of thin amorphous (Gd1−xCox)1−yMoy films

The influence of the molybdenum content of thin amorphous (Gd_1?xCo_x)_1?yMo_y films was studied. Samples were prepared with an r.f sputtering technique with values of x ranging from 0.66 to 0.97 and y ranging from 0.04 to 0.14. It was found that the concentration of molybdenum influences the saturation magnetization, the g factor and the uniaxial anisotropy field. The anisotropy constant is greatly influenced by molybdenum, especially near the compensation concentration.     

MD simulations of amorphous SiO2 thin film formation in reactive sputtering deposition processes

Silicon Dioxide (SiO₂) thin film deposition processes were studied with the use of classical Molecular Dynamics (MD) simulations combined with Monte Carlo (MC) simulations. The MC simulations are shown to efficiently emulate thermal relaxation processes during deposition. Dependence of deposited film properties on the incident kinetic energies is examined from the numerical simulations.     

CuGaSe2 thin films for photovoltaic applications

Of the I-III-VI₂ group chalcopyrites, CuInSe₂ has already proved its suitability for thin film solar cells owing to its excellent optical and transport properties. CuGaSe₂ is expected to exhibit comparable properties from this point of view. With its band gap of 1.7 eV it is a candidate for use in photovoltaic tandem systems.

The preparation of CuGaSe₂ thin films by means of the vacuum evaporation of the constituent elements (four-temperature method) is described. The structural, electrical and optical properties of these films were investigated. Secondary electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction examination and measurements of the optical transmission, resistivity and thermoelectric power were used to determine the film properties relative to the preparation parameters and stoichiometry. The growth conditions were optimized for solar cell applications. Heterojunctions were prepared by the in situ evaporation of Zn_xCd_1−xS onto the CuGaSe₂ films. The characteristic data of the cells are a short-circuit current of 6 mA and an open-circuit voltage of 620 mV at an illumination at air mass 1.5 on an area of 1 cm².     

Microstructure and electrochemical properties of magnetron-sputtered LiCoO2/LiNiO2 multi-layer thin film electrode

LiCoO₂ single-layer and LiCoO₂/LiNiO₂ multi-layer thin film electrodes were successfully fabricated by magnetron sputtering. Their microstructure and electrochemical properties were investigated. Once annealed, both films had the (0 0 3) preferred orientation to minimize the surface energy. The initial discharge capacity of the multi-layer thin film was approximately 53.1 μAh/cm² μm, which was higher than that of the LiCoO₂ single-layer thin film having similar thickness. The capacity retention of the multi-layer thin film was superior to that of the single-layer thin film. These findings indicate that the multi-layer thin film is a promising cathode material for the fabrication of high-performance thin film batteries.     

Sn1−x Pbx O2 sputtered thin films as photoanodes for photoelectrochemical cells

Pb_x Sn_1?x O₂ thin films have been prepared by glow discharge. These films have been characterized by X-ray and microprobe analysis. The photoelectrochemical behaviour shows anodic and cathodic corrosion either in the dark or under illumination. The onset of photocurrent is pH dependant. Photocurrent versus the wavelength is shifted to the visible range of the spectrum when lead content increases.     

Comparison of the photoelectric properties of the system TiO2−x with the system TiO2−xFx

The system TiO_2?x has been prepared and its photoelectric properties have been characterized as a function of x. A comparison is made between the members of the systems TiO_2?x and TiO_2?xF_x. The role of vacancies is discussed in connection with the differences between the photoelectric behaviors observed in the two systems.     

Preparation of paratellurite TeO2

Raw materials for the growth of Paratellurite TeO₂ single crystal were prepared by oxidizing metallic Te with boiling concentrated nitric acid, and large single crystals of Paratellurite were successfully grown from the melt. Simulation experiments of the crystal pulling demonstrated the fluid-flow conditions in the melt.     

Magnetization and crystal structure of RF-sputtered nanocrystalline CuFe2O4 thin films

Cu-ferrite films were deposited on glass substrates by RF-magnetron sputtering in pure Ar and mixture of (Ar + O₂) environment. The XRD studies of the as-deposited films indicate nanocrystalline cubic spinel structure. The observed increase in the intensity of (400) line at the expense of (220) line with increase in O₂ content is ascribed to the change in distribution of Cu and Fe-ions among tetrahedral A-site and octahedral B-sites. The highest saturation magnetization (M_S) of 264 emu/cm³ (in-plane) and 188 emu/cm³ (out of-plane) was obtained for the as-deposited films in pure Ar. The high deposition rate in reducing atmosphere leads to the formation of Cu⁺ ions which prefer occupation of the A-site in the spinel structure displacing Fe³⁺ cations to occupy the B-sites giving rise to the change in cation distribution among A and B-sites and consequently leading to high value of M_S. The decrease in M_S value with increase in oxygen content is ascribed to the decrease in film growth rate and Cu⁺ concentration which allow the cations to take up their preferable sites. The observed change in the film properties with environment is due to the presence of multivalent copper and iron ions with differing site preferences.