Growth And Photoelectric Properties Of Two-dimensional MoS2 Films Prepared By Pulsed Laser Deposition(PLD )

The pursuit of high performance electronic and/or optoelectronic devices based on two-dimensional(2D)layered materials is driven by both scientific interests and practical applications ranging from quantum information,astrophysics,environmental monitoring,to hardware development.In particular,direct growth of uniform large-scale 2D layered materials using a universal method is of vital importance for utilizing 2D layers into practical applications.Here,we report on the growth and transport properties of large-scale few-layer MoS2 back-gated field effect transistors(FETs)and the layer-dependent performance of MoS2 based photodetectors,fabricated using pulsed laser deposition(PLD)technique.Our results suggest that the PLD would be a suitable pathway to grow 2D layers for future industrial device applications.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 influence of different thickness of MoS2 films on photodetectors and the multilayer MoS2 thin films on FETs are studied.The results of the study are as follows:1.Raman spectroscopy and transmission electron microscopy results confirmed that the obtained MoS2 layers on SiO2/Si substrate are multilayers.The FETs devices exhibit a relative high on/off ratio of 5 ×102 and mobility of 0.124 cm2V-1S-1.2.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 responsivity 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.