Structural, Optical and Thermo Electrical Properties of Nanostructured Vacuum Evaporated CdS Thin Films

Nano structured thin films having different thickness of CdS were deposited by thermal evaporation techniques, onto precleaned amorphous glass substrate at room temperature. The structural properties of films were evaluated by XRD, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The quantitative analysis was done by Energy Dispersive Analysis for x-ray to determine atomic % of the material used. The optical band gaps of the films were measured by using optical absorption spectra. Thermo Electrical parameters such as Fermi energy (0.098 to 0.006 eV), absorption coefficient (1.04 to 1.16) have been estimated. The x-ray diffraction analysis confirms that films are polycrystalline in nature having orthorhombic structure with a preferential orientation along the (040) plane. The degree of such a preferred orientation was found to increase with film thickness. The lattice parameters (a= 14.315, b = 14.568 and c= 14.074 angstrom) and crystallite size (ID) were calculated and found to be 242.9 nm. Unit cell volume is found to be 2935. SEM investigation confirms that films were uniformly deposited over the surface and particles were granular in nature. The particle size was determined by using SEM and found to be 6.88 - 10.86 nm. It is found that CdS is direct band gap material having value of 2.42 eV.