A modified CVD method for the synthesis of monolayer MoS₂ and photoelectric improvement by HfO₂ passivation

Abstract Molybdenum disulfide (MoS₂) is an emerging class of new materials with a wide range of potential practical applications. However, the uncontrollability of monolayer MoS₂ synthesized by traditional chemical vapor deposition method and the low responsivity of MoS₂ photodetectors limit its further development in the field of photoelectric detection. To achieve controlled growth of monolayer MoS₂ and construct MoS₂ photodetectors with a high responsivity, we propose a novel single crystal growth strategy of high-quality MoS₂ by controlling the Mo to S vapor ratio near the substrate, and deposit a layer of hafnium oxide (HfO₂) on the surface of MoS₂ to enhance the performance of the pristine metal-semiconductor-metal structure photodetector. At a reverse bias of 8 V, the HfO₂ passivated MoS₂ photodetector features an extremely high responsivity of 1201 {AW}⁻¹, a response time of around 0.5 s, and a detectivity of 7.7×{10}¹¹ Jones. Meanwhile, we deeply investigate the effect of the HfO₂ layer on the performance of the fabricated MoS₂ 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 MoS₂ photodetectors and accelerate the development of MoS₂-based optoelectronic devices.