Improved Temporal Response of MoS Photodetectors by Mild Oxygen Plasma Treatment.

Temporal response is an important factor limiting the performance of two-dimensional (2D) material photodetectors. The deep trap states caused by intrinsic defects are the main factor to prolong the response time. In this work, it is demonstrated that the trap states in 2D molybdenum disulfide (MoS) can be efficiently modulated by defect engineering through mild oxygen plasma treatment. The response time of the few-layer MoS photodetector is accelerated by 2-3 orders of magnitude, which is mainly attributed to the deep trap states that can be easily filled when O or oxygen ions are chemically bonded with MoS at sulfur vacancies (SV) sites. We characterized the defect engineering of plasma-exposed MoS by Raman, PL and electric properties. Under the optimal processing conditions of 30 W, 50 Pa and 30 s, we found 30-fold enhancements in photoluminescence (PL) intensity and a nearly 2-fold enhancement in carrier field-effect mobility, while the rise and fall response times reached 110 ms and 55 ms, respectively, at the illumination wavelength of 532 nm. This work would, therefore, offer a practical route to improve the performance of 2D dichalcogenide-based devices for future consideration in optoelectronics research.