Structural and optical properties of Zn–In–Te thin films deposited by thermal evaporation technique

Abstract

Annealing effects on structural and optical properties of the thermally evaporated Zn–In–Te (ZIT) thin films have been investigated. The structural and the compositional analyses were carried out by means of X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDXA). The as-grown and annealed ZIT films had polycrystalline structure and the preferred orientation changed from (220) to (112) direction with increasing annealing temperature. The optical properties and constants were determined by transmittance measurements in the wavelength range of 200–2000nm. The effect of annealing on the optical parameters was determined by using Single Oscillator Model (SOM), Envelope Model (EM) and Cauchy Method. The absorbance studies revealed that the films had three distinct transitions in the high absorption region because of the tetragonal distortion, and that was used to evaluate the splitting energies of crystal-field and spin–orbit splitting. The fundamental optical band gap values were found to be lying in the range of 1.51 and 1.72eV and the notable change of the band gaps due to annealing temperatures was observed. Finally, the Urbach energies were calculated and it was observed that the band tail energies were increasing with increasing annealing temperature.