Study of substrate dependent microstructural properties of sputtered Mo/CZTS heterojunctions using X ray diffraction

Abstract

Thin films of CZTS (Cu₂ZnSnS₄) were deposited using radiofrequency sputtering (RF) at varying sputtering powers on soda lime glass coated with molybdenum (Mo). Direct current (DC) sputtering was used to deposit Mo thin films at various sputtering powers. Rapid thermal processing (RTP) was employed to anneal the thin films that had been deposited at temperatures of 300, 400, and 500 °C. X ray diffraction (XRD) technique was used to probe thin films structurally. The microstructural characteristics, such as crystallite size and microstrain, were calculated. These properties, particularly crystallite size and microstrain, are critical in future applications as an absorber layer in a thin film solar cell. A comprehensive comparative study has been carried out using Scherrer method, Williamson-Hall method, Halder-Wagner method, Size-Strain plot method, and Wagner-Aqua method. Crystallite size and microstrain obtained in this work shows strong dependence on preferential orientation of DC sputtered Mo base layer. Crystallite size, microstrain measured shows similar trends. Microstrain obtained exhibits systematic relationship with variation in deposition parameters of DC sputtered Mo thin films and RF sputtered CZTS thin films. This dependency of CZTS microstructural features on base layer Mo growth conditions can be used in the future to apply CZTS as a solar cell absorber layer.