Effect of Annealing Temperature on the Structural and Optical Properties of ZnS Thin Films

In this paper, we have demonstrated the phase transformation from cubic ZnS to hexagonal ZnO by high temperature thermal annealing. The films were grown on Si (001) substrate by thermal evaporation system using ZnS powder as source material. The grown films were characterized using X-Ray diffraction (XRD), Photoluminescence (PL), Four Point Probe, Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Diffraction (EDX). As-deposited ZnS film has mixed phases but high temperature annealing leads to transition from cubic to hexagonal phase. O atom attained sufficient energy during annealing and replaced the S atom in the crystal. PL spectra of as-grown sample exhibits a characteristics green emission at 2.4 eV of ZnS but annealed samples consist of band to band and defect emission of ZnO at 3.29 eV and 2.5 eV respectively.