Growth Optimization and Study on Structural, Morphological, Optical and Electrical Properties of As-Deposited Zinc Sulfide Thin Films Fabricated by Radio-Frequency Magnetron Sputtering Technique at Room Temperature

Abstract

The deposition of Zinc Sulfide (ZnS) thin films is optimized using a radio-frequency (RF) magnetron sputtering technique with variable RF power to minimize deposition steps and lower the fabrication costs. Room temperature as-deposited film growth optimization is conducted by studying their structural, morphological, optical, and electrical properties. The target power and deposition rate were related by a slope of 0.1648 and a linear correlation coefficient (R) of 0.9893. Only one significant peak for the films in the XRD pattern indicated that the films are of a single crystalline structure. All the deposited thin films exhibited a ZB structure. It is observed that the micro-strain ranged from 36.00x10-3 to 4.14x10-3, and that of dislocation density ranged from 6.68 to 0.08 Line/cm2. The optical energy band gaps of as-deposited ZnS films at different deposition power were found from 3.31 to 3.37 eV. The average transmittance percentage was increasing from 71.63% to 84.29%, above 400 nm wavelength. The films exhibited n-type conductivity with bulk carrier density in the order of 1012 cm-3. The carrier concentration and mobility ranged from 2.84x1011 to 3.98x1012 cm-3 and 1.06 to 27.68 cm2/Vs, respectively. The minimum and maximum resistivity of 1.01x104 and 2.52´105 Ω-cm were noted for the film deposited at 90 and 60W power, respectively.