In the present study, the effect of S and Se substitution on structural, electrical and optical properties of AgGa(Se2-xSx) thin films has been investigated. AgGa(Se0.5S0.5 )2 thin films were prepared by using the thermal evaporation method. X-ray diffraction (XRD) analysis has revealed that the transformation from amorphous to polycrystalline structure took place at about 450 oC. The detailed information about the stoichometry and the segregation mechanisms of the constituent elements in the structure has been obtained by performing both energy dispersive X-ray analysis (EDXA) and X-ray photoelectron spectroscopy (XPS) measurements. AgGaSe2 thin films were deposited by using both electron-beam (e-beam) and sputtering techniques. In e-beam evaporated thin films, the effect of annealing on the structural and morphological properties of the deposited films has been studied by means of XRD, XPS, scanning electron microscopy (SEM) and EDXA measurements. Structural analysis has shown that samples annealed between 300 and 600 oC were in polycrystalline structure with co-existance of Ag, Ga2Se3, GaSe, and AgGaSe2. The variation of surface morphology, chemical composition and bonding nature of constituent elements on post-annealing has been determined by EDXA and XPS analyses. AgGaSe2 thin films were also prepared by using sputtering technique. XRD measurements have shown that the mono-phase AgGaSe2 structure is formed at annealing temperature of 600 oC. The crystal-field and spin-orbit splitting levels were resolved. These levels around 2.03 and 2.30 eV were also detected from the photospectral response measurements. Thin films of Ag-Ga-S (AGS) compound were prepared by using AgGaS2 single crystalline powder and deposition of the excess silver (Ag) intralayer with double source thermal evaporation method. As a consequence of systematic optimization of thickness of Ag layer, Ag(Ga,S) with the stoichiometry of AgGa5S8 and AgGaS2 were obtained and systematic study to obtain structural, electrical and optical properties was carried out.

abstract: Amorphous oxide semiconductors are promising new materials for various optoelectronic applications. In this study, improved electrical and optical properties upon thermal and microwave processing of mixed-oxide semiconductors are reported. First, arsenic-doped silicon was used as a model system to understand susceptor-assisted microwave annealing. Mixed oxide semiconductor films of indium zinc oxide (IZO) and indium gallium zinc oxide (IGZO) were deposited by room-temperature RF sputtering on flexible polymer substrates. Thermal annealing in different environments - air, vacuum and oxygen was done. Electrical and optical characterization was carried out before and after annealing. The degree of reversal in the degradation in electrical properties of the thin films upon annealing in oxygen was assessed by subjecting samples to subsequent vacuum anneals. To further increase the conductivity of the IGZO films, Ag layers of various thicknesses were embedded between two IGZO layers. Optical performance of the multilayer structures was improved by susceptor-assisted microwave annealing and furnace-annealing in oxygen environment without compromising on their electrical conductivity. The post-processing of the films in different environments was used to develop an understanding of mechanisms of carrier generation, transport and optical absorption. This study establishes IGZO as a viable transparent conductor, which can be deposited at room-temperature and processed by thermal and microwave annealing to improve electrical and optical performance for applications in flexible electronics and optoelectronics. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2011