Optical Properties of CdTe:In Thin Films Deposited by PVD Technique

Abstract

CdTe:In thin films on glass substrates were obtained by physical vapor deposition. Thin films were obtained with different thicknesses (by setting of different deposition time τ) at the constant temperature of substrate and temperature of evaporation. Identification of CdTe thin films was performed by the measurements of spectral distribution of optical transparency. Region of the fundamental absorption was observed in the transmission spectra. The films are characterized by high transparency in near infrared region and moderate transmission coefficient which varies from 52 % to 85 %. All of the films demonstrated very sharp absorption edge near 800 nm. Moreover, observed interference in optical transparency spectra is an indication of the uniform thickness of deposited films. The Swanepoel method is used to calculate maximum ТМ() and minimum Tm() transmission curves by parabolic interpolation to experimentally determined positions of interference maxima and minima. Sharp increase of the refraction index at wavelengths  1000 nm is due to decreased transmission near the fundamental absorption edge of thin films of indium-doped cadmium telluride. Main optical constants were determined, such as theoretical film thickness, refraction index, and absorption coefficient.