Synthesis of thermally evaporated ZnSe thin film at room temperature

Abstract

Zinc selenide (ZnSe) thin film on glass substrates were prepared by thermal evaporation under high vacuum using the quasi-closed volume technique at room temperature (300 ± 2 K). The deposited ZnSe properties were assessed via X-ray diffraction, atomic force microscope (AFM), UV-Vis specrophotometry, Raman spectroscopy, photo-luminescence, Fourier transform infrared spectroscopy (FT-IR) and spectroscopic ellipsometry. The X-ray diffraction patterns of the film exhibited reflection corresponding to the cubic (111) phase (2θ = 27.20°). This analysis indicated that the sample is polycrystalline and have cubic (Zinc blende) structure. The crystallites were preferentially oriented with the (111) planes parallel to the substrates. The AFM images showed that the ZnSe films have smooth morphology with roughness 6.74 nm. The transmittance spectrum revealed a high transmission of 89% in the infrared region (≥ 600 nm) and a low transmission of 40% at 450 nm. The maximum transmission of 89.6% was observed at 640 nm. Optical band-gap was calculated from the transmission data of specrophotometry, photo-luminescence and ellipsometry and was 2.76, 2.74 and 2.82 eV respectively. Raman spectroscopic studies revealed two longitudinal optical phonon modes at 252 cm -1 and 500 cm -1. In photoluminescence study, the luminescence peaks was observed at 452 nm corresponding to band to band emission. FT-IR study illustrated the existence of Zn-Se bonding in ZnSe thin film. The optical constants were calculated using spectroscopic ellipsometry and were determined from the best fit ellipsometric data in the wavelength regime of interest from 370–1000 nm. These results manifested excellent room temperature ZnSe synthesis and characteristics for opto-electronics technologies.