Refractive index of CdTe1-xSex thin films estimated by Swanepoel's method

Abstract

CdTe1-xSex thin films were deposited on a quartz and silicon substrate using the method of high-frequency magnetron sputtering. The chemical composition analysis and crystal structure refinement were examined using X-ray fluorescence spectroscopy and X-ray diffraction data. CdTe1-xSex thin films with x < 0.7 are crystallized in hexagonal structure (structure type – ZnO, space group P63mc (No. 186)) and in cubic structure (structure type – ZnS, space group F-43m (No. 216)) with x < 0.35. Unit-cell parameters decrease with increasing Se content in CdTe1-xSex thin films. The values of the optical band gaps for CdTe1-xSex thin films were estimated using the Tauc plot and from the maximum position of the first derivative of the transmittance dT/dλ. The study of optical functions is performed on the basis of the transmission spectrum measured experimentally using the Swanepoel's method. The spectral behavior of the optical functions, such as refractive index and real part of dielectric function is established. The dispersion of the refractive index is discussed in terms of the Wemple and Di Domenico single oscillator model.