Structural Properties of Vacuum Evaporated ZnS Thin Films

Abstract

Thin films of zinc sulphide was deposited on to a glass substrate which is well rinsed in a 10 -6 Torr vacuum. Quartz crystal monitor method was used to determine the film thickness. ZnS films and a typical diffraction pattern of the as-grown ZnS thin films were subjected to X-Ray Power Diffraction (XRD) analysis. A ZnS thin film of lower and higher thicknesses has an amorphous structure and polycrystalline nature with cubic structure respectively. Evaluation of the structural parameters such as micro strain, lattice constant (a), inter-planar distance (d), dislocation density and grain size (D) have been carried out. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) was employed to find the grain size of the particles and to study about the surface smoothness. Films with different thicknesses and their grain sizes were calculated. The resolution and magnification was kept at 20µm and 5000x respectively and the SEM micrographs of different thicknesses were analyzed. It is clearly observed that the tiny Nano sized grains are engaged in a fibrous-like structure. This clearly points towards the glassy nature and amorphous phase of ZnS thin films. The AFM micrograph indicates that as the thickness increases, the particle size and the surface roughness of ZnS thin films also increases. The Energy-dispersive X-ray spectroscopy (EDAX) confirms the presence of sulphur, zinc and oxygen in all the films.