Band-Gap Tuning Of Electron Beam Evaporated Cds Thin Films

The effect of evaporation rate on structural, morphological and optical properties of electron beam evaporated CdS thin films have been investigated. CdS thin film deposited by electron beam evaporation method in 12nm/min and 60nm/min evaporation rates on glass substrates. X-ray diffraction, scanning electron microscopy, UV-Vis-NIR spectroscopy and Atomic Force Microscopy were used to characterize thin films. The x-ray diffraction analysis confirms that films have polycrystalline hexagonal phase and exhibited preferred orientation along the (002) plane. The crystallite size were calculated and found to be increased from 23 nm to 30 nm by increasing deposition rate. Results of Atomic Force Microscopy revealed that the RMS roughness values of the CdS films decreased as deposition rate increased. The relation between deposition rates and optical properties of deposited films was investigated. It was found that stoichiometric properties and band gap values of the deposited films are correlated to deposition rates. These dependencies are associated to the Cd/S ratio variation by deposition rate. The optical band gap values of CdS films increased slightly in a range of 2.32–2.34 eV for deposition rate varied from 12nm/min and 60nm/min .