Photoconductivity of acid exfoliated and flash-light-processed MoS₂ films

MoS₂ has been studied intensively during recent years as a semiconducting material in several fields, including optoelectronics, for applications such as solar cells and phototransistors. The photoresponse mechanisms of MoS₂ have been discussed but are not fully understood, especially the phenomenon in which the photocurrent slowly increases. Here, we report on a study of the photoresponse flash-light-processed MoS₂ films of different thicknesses and areas. The photoresponse of such films under different light intensities and bias voltages was measured, showing significant current changes with a quick response followed by a slow one upon exposure to pulsed light. Our in-depth study suggested that the slow response was due to the photothermal effect that heats the MoS₂; this hypothesis was supported by the resistivity change at different temperatures. The results obtained from MoS₂ films with various thicknesses indicated that the minority-carrier diffusion length was 1.36 µm. This study explained the mechanism of the slow response of the MoS₂ film and determined the effective thickness of MoS₂ for a photoresponse to occur. The method used here for fabricating MoS₂ films could be used for fabricating optoelectronic devices due to its simplicity.