Synthesis of Monolayer MoS2 Films and Tuning Its Photoelectric Properties via Interface Engineering

Two-dimensional (2D) materials have received considerable attention for their applications in nextgeneration optoelectronics but are limited by the synthesis of large-area films and the challenges in device optimization. In this study, a uniform MoS 2 monolayer film was synthesized by a simple chemical vapor deposition (CVD) method. Phototransistors based on the resulting MoS 2 films were fabricated and their photoelectric properties were compared with that of a device with synthesized triangular MoS 2 sheets. The results show that the photoresponsivity of the film-based phototransistor is 1180 mA/W at a power density of 1 mW/cm 2 , far exceeding (15 times) that of the sheet-based phototransistor. Furthermore, with mild vacuum annealing, the photoresponsivity and photoresponse speed in the film-based phototransistor demonstrated a simultaneous increase, in which the photoresponsivity reached up to 105 A/W with a decreased photoresponse/recovery time from 9 s/22 s to 5 s/8 s under illumination. This satisfactory improvement after vacuum annealing can be attributed to the removal of oxygen atoms from sulfur vacancies and a reduced inherent van der Waals gap at the MoS 2 /Au interface, which facilitates the trapping of photogenerated electrons and promotes carrier separation. Our work provides a promising strategy for high-performance 2D photodetectors via rational synthesis and interface engineering.