A modified CVD method for the synthesis of monolayer MoS 2 and photoelectric improvement by HfO 2 passivation.

Molybdenum disulfide (MoS 2 ) is an emerging class of new materials with a wide range of potential practical applications. However, the uncontrollability of monolayer MoS 2 synthesized by traditional chemical vapor deposition method and the low responsivity of MoS 2 photodetectors limit its further development in the field of photoelectric detection. To achieve controlled growth of monolayer MoS 2 and construct MoS 2 photodetectors with a high responsivity, we propose a novel single crystal growth strategy of high-quality MoS 2 by controlling the Mo to S vapor ratio near the substrate, and deposit a layer of hafnium oxide (HfO 2 ) on the surface of MoS 2 to enhance the performance of the pristine metal-semiconductor-metal structure photodetector. At a reverse bias of 8 V, the HfO 2 passivated MoS 2 photodetector features an extremely high responsivity of1201AW-1,a response time of around 0.5 s, and a detectivity of7.7×1011Jones.Meanwhile, we deeply investigate the effect of the HfO 2 layer on the performance of the fabricated MoS 2 photodetector and propose a physical mechanism to interpret the obtained experiment results. These results might facilitate a better understanding on the performance modulation of the MoS 2 photodetectors and accelerate the development of MoS 2 -based optoelectronic devices.