The influence of deposition rate on optical and microstructural characteristics of nanostructured ZnSe films prepared by thermal evaporation technique

In this research, ZnSe thin films were deposited on glass substrate by the thermal evaporation method with deposition rates of 0.2, 0.4, 0.6, and 0.8 nm/s and with a constant thickness of 250 nm. All samples were annealed for 100 minutes at a temperature of 400 °C. Various techniques such as UV–Vis spectrophotometer, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM) were used to investigate different physical parameters such as energy band gap, refractive index, extinction coefficient, dielectric constant, and porosity of the ZnSe thin films.  The influence of the deposition rate on the mentioned parameters was investigated. The XRD patterns showed that the ZnSe thin films have a cubic structure. The structural parameters such as lattice constant, crystallite size, strain, and dislocation density were determined for different samples. The maximum average transmittance of %93.1 in the visible wavelength region was obtained for the deposition rate of 0.6 (nm/s). The optical band gap was calculated using the derivation of absorption spectrum fitting (DASF) method, and the values of the energy bandgap were obtained in the range of 3.710.01 to 3.980.01 eV. The XRD results acquired from the Williamson-Hall method showed that the crystallites size and strain of different samples were achieved in the range of 21.61.1 to 42.92.3 nm and (0.610.02)×10-3 to (2.890.04)×10-3, respectively. Finally, the relation between the optical and microstructural properties of the ZnSe films was studied.