Influence of angle deposition on the properties of ZnTe thin films prepared by thermal evaporation

摘要

Thin films of ZnTe were deposited at angles of 0 degrees, 20 degrees, 40 degrees, 60 degrees and 80 degrees by thermal evaporation. The chemical, structural, morphological, optical, and photocurrent properties of ZnTe thin films were investigated. The elemental composition of the films was investigated by energy dispersive x-ray spectroscopy (EDX) and x-ray photoelectron spectroscopy (XPS). EDX and XPS analyses showed that at lower angles (0 degrees and 20 degrees), the deposited films were Te-rich, at 40 degrees, the deposited film was nearly stoichiometric; and at higher angles (60 degrees and 80 degrees), the deposited films were Zn-rich. X-ray diffraction (XRD) analysis showed that all films were polycrystalline. X-ray diffraction patterns showed that lower-angles-deposited films had an extra peak at 2 theta = 36.47 degrees that belongs to Te element. Atomic force microscopy analysis revealed that the surface roughness of films was increased by increasing the deposition angle from 0 degrees to 80 degrees because shadowing effect raised due to an oblique angle. It was observed that higher-angles-deposited films (ZnTe-60 degrees, and ZnTe-80 degrees) showed less transmittance and high reflectance compared to lower-angles-deposited films because of high metallic Zn content in these films. Current voltage (I-V) measurements showed that nearly stoichiometric (ZnTe-40 degrees) film showed better photocurrent response compared to non-stoichiometric films (ZnTe-0 degrees, ZnTe-20 degrees, ZnTe-60 degrees, and ZnTe-80 degrees).