Effect of substrate temperature on photoconductivity, structural, and optical properties of vacuum evaporated Zinc Telluride films

Zinc telluride thin films were prepared by vacuum evaporation onto glass and quartz substrates at different substrate temperatures. The effect of the substrate temperature on the structural, optical and photoconductivity properties were studied. The crystalline structure was found to be cubic structure with average lattice parameters ranged between 6.140 ± 0.005 and 6.081 ± 0.005 Å. The film crystallites were preferred oriented with (1 1 1) planes and the crystallite size increased with temperature. Optical properties were performed in the spectral range from 300 to 2500 nm to determine the optical constants. The band gap increased from 2.62 to 3.24 eV as the substrate temperature varied from 298 to 510 K. The photoconductivity obeyed two distinct conduction mechanisms. At high fields, the photoconduction obeyed Poole–Frenkel type and at low fields it was ohmic. The regions of Poole–Frenkel conductivity were found to extend to lower fields with increased of ambient temperatures.

► ZnTe thin films were prepared by vacuum evaporation on quartz substrates.
► Highly (1 1 1) oriented ZnTe films were grown at different substrate temperatures.
► Optical properties were performed in the spectral range 300–2500 nm.
► Photoconductivity obeyed two distinct conduction mechanisms.
► Regions of conductivity were extend to lower fields with ambient temperatures.