Effect of Deposition Time On Chemically Synthesized CuS Thin Film for Photodetectors

Abstract

In the current era, transition metal chalcogenides have attracted much attention because of their capability of large-area deposition with diverse applications in the field of optoelectronic, photoelectric conversion, solar cells, and lithium-ion batteries. In this work, covellite copper sulfide (CuS) thin film has been deposited on the glass substrates by the low-cost chemical bath deposition (CBD) method with 1:4 molar ratio of copper and sulfur at 60 °C with a variation of deposition time 1 hr, 2 hr, and 3 hr. The structural, electrical, and optical properties of CuS thin film deposited at different deposition times have been investigated. XRD confirms the presence of the covellite phase of copper sulfide thin film. Raman spectroscopy reveals a prominent peak at 475 cm-1, corresponding to the vibration of the stretching mode of the S-S bond, which depicts the formation of the covellite phase of copper sulfide thin film. The crystallinity of CuS thin film is found to be increased with an increase in the deposition time. The Hall effect measurement system has revealed the p-type nature of CuS thin film. The carrier concentration of CuS thin film is found to be decreased with an increase in deposition time. The mobility of CuS thin film has been enhanced up to 29.49 cm2/ (V.s) with an increase in deposition time due to an increase in crystallite size. Hence, the resistivity of CuS thin film decreases with an increase in deposition time due to the free movement of charge carriers. The current-voltage plot shows the ohmic nature of CuS thin film, indicating a good metal-semiconductor contact that allows free movement of charge carriers between metal and semiconductor. The CuS thin film, deposited for 3 hr, exhibits the highest photocurrent under the illumination of visible light. The CuS thin film, deposited for 3 hr, possesses a carrier concentration of 7.4×1018 cm-3, and mobility of 29.49 cm2/(V.s), which can be a suitable candidate for fabrication of photodetector.