Band gap energy determination by Absorption Spectrum Fitting (ASF) procedure and Lattice parameter for different composition of CdxZn1-xS thin films

Abstract

Cadmium zinc sulphide (Cd_xZ_1-xS) thin films have been chemically prepared unto glass substrates from CdS/ZnS bilayer and its post thermal annealing. Structural and Optical properties of the deposited Cd_xZ_1-xS thin films were studied using X-ray diffraction (XRD) and UV-Vis spectroscopy. The X-ray diffraction revealed a cubic structure with (111) preferential orientation. The lattice constants was determined using the Nelson-Riley plot analysis and the result obtained showed that the lattice parameters increase with increase in Cd composition. Starting with the Tauc model, the absorption spectrum fitting technique (ASF) was used in obtaining the optical band gap energy. The values of the direct band gap energy were seen to be in the range of 3.67 and 3.77 eV and depend on Cd_xZn_1-xS composition. The reported optical properties of Cd_xZn_1-xS ternary compound prepared under this present condition make the thin films useful as a buffer layer in thin film solar cells.

Keywords: Band gap energy, Williamson-Hall, Crystallite size.