Kalpathy B. Sundaram

Characterization and optimization of zinc oxide films by r.f. magnetron sputtering

Abstract Zinc oxide films were deposited by a r.f. magnetron sputtering using a zinc oxide target. The deposited films were characterized as a function of deposition temperature, pressure, argon-oxygen gas flow ratio, target-substrate distance. The deposition conditions were optimized to give good quality films suitable for the fabrication of surface acoustic wave device. The films deposited at temperatures as low as 250 °C yielded surface acoustic wave device quality.

Deposition and optical studies of silicon carbide nitride thin films

Thin films of silicon carbide nitride (SiCN) have been prepared by reactive radioactive frequency (r.f.) sputtering using SiC target and nitrogen as the reactant gas. Deposition rates are studied as a function of deposition pressures and argon-nitrogen flow ratios. The optical absorption studies indicated the band edge shifting of the films when the nitrogen ratios are increased during deposition. Fourier transform infrared spectroscopy (FTIR) analysis on the films indicated several stretching modes corresponding to SiC, SiN and CN compositions.

Work function determination of zinc oxide films

Zinc oxide-silicon heterojunctions were fabricated using both n- and p-type silicon. The zinc oxide films were deposited by the magnetron sputtering process at various substrate temperatures to form these devices. The electrical properties of these devices were measured and the work function of the zinc oxide was evaluated from these properties.

A Highly Efficient 200 000 RPM Permanent Magnet Motor System

This paper presents the development of an ultra-high-speed permanent magnet synchronous motor (PMSM) that produces output shaft power of 2000 W at 200 000 rpm with around 90% efficiency. Due to the guaranteed open-loop stability over the full operating speed range, the developed motor system is compact and low cost since it can avoid the design complexity of a closed-loop controller. This paper introduces the collaborative design approach of the motor system in order to ensure both performance requirements and stability over the full operating speed range. The actual implementation of the motor system is then discussed. Finally, computer simulation and experimental results are provided to validate the proposed design and its effectiveness

X-ray and electron diffraction studies of chemically vapour-deposited tin oxide films

Abstract Transparent conducting tin oxide films were prepared by a chemical vapour deposition technique which was carried out by the oxidation of stannous chloride. The films were deposited at various substrate temperatures in the range 350–500°C. X-ray and electron diffraction studies indicated that the films were polycrystalline. Films deposited at higher substrate temperatures showed better crystallinity than those deposited at lower temperatures.

Optical absorption studies on tin oxide films

Transparent electrically conducting SnO2 films were prepared by the chemical vapour deposition technique. The films were deposited at substrate temperatures of 400, 450 and 500 degrees C by stannous chloride oxidation. The optical absorption studies, using unpolarised light, indicated that the deposition temperature is an important parameter influencing the optical properties of the films. The absorption edge for the films occurs at about 3.7 eV. The films also indicated direct transitions at about 3.95 eV and indirect transitions at about 3.27 eV.

Deposition and x-ray photoelectron spectroscopy studies on sputtered cerium dioxide thin films

Cerium dioxide is a rare earth oxide material that can be useful in various optical and electronic applications because of its high refractive index and its dielectric constant. The purpose of this study was to conduct an x-ray photoelectron spectroscopy analysis of sputtered cerium dioxide thin films. The thin films were deposited onto glass substrates using rf magnetron sputtering. A cerium dioxide target was used and various oxygen–argon gas flow ratios under different sputtering power levels were used for deposition. The results presented here characterize the properties of the rf sputtered cerium dioxide thin films under different deposition conditions.

Characterization and optimization of cerium dioxide films deposited by r.f. magnetron sputtering

Abstract Cerium dioxide (CeO2) films were deposited on glass substrates by an r.f. magnetron sputtering process. The deposition rates were studied as a function of the molar fraction of oxygen in the system for various input power levels. The deposition conditions were optimized to obtain good quality films for optical transmission.

Polishing mechanism of tantalum films by SiO 2 particles

Dishing and erosion are major problems in conventional chemical mechanical planarization of copper/barrier layers. Understanding the polishing mechanism of the different materials involved can assist in providing a solution to these issues. Chemical mechanical polishing of tantalum was performed using alumina and silica particles dispersed in deionized water at pH 6. Tantalum shows a higher removal rate in silica slurry compared to alumina slurry. To examine the polishing mechanism of tantalum in silica slurry, the surface structure of the film was investigated by X-ray photoelectron spectroscopy (XPS). Various electrochemical techniques were used to characterize the surface film formation, dissolution and the interaction between silica particles and tantalum film. XPS and electrochemical results indicate that tantalum film may react with silica particles to form Ta-O-Si bonds on the surface. The mechanical tearing of Ta-O-Si bonds leads to the removal of Ta2O5 as a lump, resulting in higher removal rates of tantalum in silica slurry.

Chemical vapour deposition of tin oxide films and their electrical properties

Transparent electrically conducting SnO2 films were prepared by chemical vapour deposition technique. The films were obtained at various deposition temperature ranging from 350 to 500 degrees C by stannous chloride oxidation. The SnO2 films thus produced have a conductivity of 50-700 (ohm cm)-1, an n-type carrier concentration of 1*1019-6*1020 cm-3 and a Hall mobility of 7.8-31.2 V-1 s-1 depending on the deposition conditions. The studies on the variation of conductivity with temperature indicated two donor activation energies for the films.