Structure, surface morphology and optical properties of CuxZn1-xS/Au NPs layer for photodetector application

Abstract

CuZnS and CuZnS/Au NPs layer with different Cu/Zn content thin films have been deposited on heated glass substrate by spray pyrolysis technique at 330 °C and annealed at 450 °C for 1 hour. X-ray diffraction (XRD) results reveals that the structures of all prepared thin films are polycrystalline in nature, with preferential growth orientation along (111) plane corresponding to the cubic ZnS (sphalerite). Two low crystallinity of crystallographic phases corresponding to hexagonal CuS and monoclinic Cu2S were appeared with Cu/Zn different content. Strong diffraction peak of Au NPs appeared in CuZnS/Au NPs layer structure corresponding to the cubic Au gold phase oriented along (111) plane. Structure parameters such as crystallite size and number of crystalline, dislocation density and micro strain have been determined. Scanning Electron Microscopy (SEM) and Atomic force microscope (AFM) images of CZS, and CZS/Au NPs thin films shows smooth, uniform morphology and plated regularly with no detectable micro-cracks. The roughness and r.m.s. roughness was increased with increase of Cu/Zn content from 1.95 nm to 4.36 nm respectively, while it decreased with the exists of Au NPs layer from 20.9nm to 3.99 nm. The energy dispersion x-ray spectroscopy spectra demonstrate the stoichiometry of the deposited films. The optical properties results exhibits red shifted in the fundamental absorption edge towards low energies of CZS (Cu/Zn content) and CZS/Au Nps layer thin films. The optical energy gap has been decreased from (2.56 to 2.34 eV, and 2.62 to 2.32 eV) with respect to Cu/Zn content and Au Nps layer, respectively.