Layer-dependent photoresponse of 2D MoS2 films prepared by pulsed laser deposition

Due to the layered structure and thickness-dependent bandgap of MoS2, it is intriguing to investigate the layer-dependent performance of MoS2 based photodetectors. In this work, centimeter-scale layered MoS2 films with different layer numbers are achieved by using pulsed laser deposition by controlling the number of laser pulses. The measurement of transport characteristics in the dark indicates a Schottky barrier contact formed at the Au/MoS2 interface. The obtained metal-semiconductor-metal MoS2 based photodetectors present a UV-to-NIR photoresponse with high stability. When the thickness of the film is decreased, the photoresponse of the MoS2 photodetectors gradually increases from multilayer to bilayer, and more importantly, a notable enhancement in the photoresponse for the monolayer can be observed. In particular, a photoresponsivity of 1.96 A W-1 is achieved in monolayer MoS2 samples under illumination with a wavelength of 300 nm. The physical mechanism responsible for the observation is discussed based on the layer dependent Schottky barrier variation and the indirect-to-direct energy band transition in MoS2. Our work provides an insight into layer-dependent optical behavior in MoS2 films, which should be helpful for developing further large-scale photosensing applications in the atomic limit.