Thickness-Dependent Structural, Electrical, and Optical Properties of ZnS Thin Films Deposited by Thermal Evaporation

Abstract

Zinc sulfide (ZnS) thin films are deposited onto an ultrasonically clean glass substrate, by using the thermal evaporation technique at room temperature. The film thickness was varied in the range from 400 nm to 1300 nm. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive analysis of X-rays (EDAX) are used to characterize the structural properties of films. The electrical and optical properties of films are characterized with a dc two-point probe, the Hall effect, and ultra-violet visible absorption spectra. The XRD spectra indicate that the thin films have polycrystalline nature and possess the cubic structure with (111) preferential orientation. The diffraction patterns are sharpen with increase in the film thickness. Scanning electron microscope data disclose that the films have nanograins approximately 97.89 nm in size. A reduction in the resistivity shows that the films are semiconductors in nature. For a film thickness of 1200 nm, the maximum mobility is 26.03 × 101 cm2/Vs, minimum resistivity is 0.08 × 106 (Ohm·cm), and band gap is 3.26 eV.  The film thickness has been optimized on the basis of the observed properties.