Photoresponsivity Enhancement of Monolayer MoS₂ by Silicon Quantum Dots

Hybrid 2D/0D structures with various 2D materials and 0D quantum dots (QDs) have been studied to overcome the limitations of 2D materials. In this work, a hybrid structure with MoS₂ and silicon quantum dots (Si QDs) as a photodetector is developed. The I–V transfer characteristics show a threshold voltage shift after decorating Si QDs on MoS₂, which results from an n-type doping effect to the MoS₂ channel from the Si QDs. The field-effect mobility of the MoS₂/Si QDs device is increased by ≈5.8 times compared with that of the bare MoS₂ device. It is understood that the mobility enhancement is attributed to the surface defect passivation of MoS₂ at the interface with Si QDs. It is observed that the photoresponsivity of the MoS₂/Si QDs structure is improved by ≈7.7 times compared with that of the bare MoS₂ device under 500 nm illumination. Additionally, it is observed that the photoluminescence (PL) intensity of MoS₂ is increased about 4.5 times after decoration of Si QDs. The band alignment as type I at the interface between the Si QDs and MoS₂ is interpreted. The mobility enhancement and the photoexcited charge transfer (CT) between the MoS₂ and the Si QDs due to the illumination lead to enhancing the photoresponsivity of the MoS₂/Si QDs hybrid structure.