No abstract

No abstract

No abstract

No abstract

The (Si)GeSn films have been grown with and without carrier gases on Si substrate using a cold-wall ultra-high vacuum chemical vapor deposition system. Material characterization of the films grown with Ar carrier gas using X-ray diffraction and transmission electron microscopy shows achievement of higher quality films. Optical characterization of the films with photoluminescence shows enhancement in material quality of the films at 350 and 400ºC growth temperatures. Increase in the pressure results in higher Sn incorporation and higher photoluminescence intensity. Spectroscopic ellipsometry data confirms the change in the GeSn bandgap towards lower energies.

The CdS:Cl thin films have been prepared using thermally evaporated, CdCl 2 -mixed CdS powder at 200°C substrate temperature. The percentage of CdCl 2 in the mixture varied from 0% to 0.20%. The electrical properties and the grain size of the deposited films were investigated. The results show that light doping, resistivity, carrier concentration, and mobility follow Seto's model for polycrystalline material. However, with heavy doping, these properties undergo a saturation trend. The saturation behavior can be understood in terms of the rapid formation of the A-center complexes in the films. The deposited films were annealed at 250°C and 300°C.The resistivity of pure and lightly doped CdS films increased with annealing temperature, whereas carrier concentration and mobility in these films decreased. However, for the higher doping concentrations, the resistivity decreased, whereas carrier concentration and mobility showed improvement. These changes in electrical properties of the deposited films with annealing and doping concentration are attributed to a reduction in the lattice defect sites in CdS upon annealing. The experimental results are interpreted in terms of a modified version of Seto's model for polycrystalline materials.

A metal-induced crystallization (MIC) technique was used to produce large-grain poly-crystalline silicon. Two sets of samples were prepared by first sputtering Al onto glass substrates. For one set of samples, hydrogenated amorphous silicon (a-Si:H) was sputtered on top of the Al without breaking the vacuum. For the second set, the samples were taken out of the vacuum chamber and exposed to the atmosphere to grow a very thin layer of native aluminum oxide before sputter depositing the a-Si:H. Both sets of samples were then annealed at temperatures between 400 and 525°C for 40 min. X-ray diffraction patterns confirmed the crystallization of the samples. Scanning Auger microanalysis was used to confirm that the a-Si:H and Al layers exchanged positions in this structure during the crystallization process. Auger mapping revealed the formation of large grain poly-silicon (10-20 m). A model is proposed to explain how the crystallization process progresses with anneal temperature.

The effect of a native silicon dioxide layer on metal-induced crystallization of hydrogenated amorphous silicon ͑a-Si:H͒ was investigated. Several samples, deposited by the plasma-enhanced chemical vapor deposition technique, were exposed to different ambients for different times to allow for the growth of SiO 2 layers of different thicknesses. Then, aluminum was used to crystallize the samples using metal-induced crystallization at temperatures far below the solid-phase crystallization temperature of a-Si. In this study, we focused on the effects of the native oxide layer on crystallization and crystallization rates of the samples, as determined by X-ray diffraction. Following crystallization, scanning electron microscopy, environmental scanning electron microscopy, energy dispersive spectroscopy, and atomic force microscopy were used to examine and compare the morphology and chemical composition of the surface of the different samples. Finally, an explanation of the findings is presented.