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

Abstract

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.