Optical and energy properties of CdSe₁₋ₓSₓ thin films obtained by the method of high-frequency magnetron sputtering

Abstract

CdSe_1-xS_x (x = 0, 0.3, 0.4, 0.6, and 1) thin films were deposited on a quartz and silicon substrate using high-frequency magnetron sputtering. X-ray diffraction analysis estimated that the CdSe_1-xS_x thin films are crystallized in a hexagonal structure [structure type – ZnO, space group P6₃mc (No. 186)]. Spectral dependence of the optical transmittance between 300 and 1500 nm of the obtained thin films at room temperature was measured. Normalized integral optical transmittance, optical band gap, spin-orbit splitting, and the value of the bowing parameter of the CdSe_1-xS_x thin films are determined. The values of the optical band gaps for CdSe_1-xS_x thin films were estimated using the two methods (by Tauc plot and dT/dλ). Concentration dependences of the energy gaps connected with the leading optical transitions in CdSe_1-xS_x (Г₈^v–Г₆^c, Г₇^v–Г₆^c) and spin-orbit splitting are studied. It is shown that the concentration dependences of main optical transitions are quadratic. The principal explanation for this seems to be the Burstein–Moss effect, which is caused by the doping atoms' excess carriers (electrons and holes).