Oxygen Driven Defect Engineering of Monolayer MoS2 for Tunable Electronic, Optoelectronic, and Electrochemical Devices

Abstract

AbstractMolybdenum disulfide (MoS2), a two‐dimensional (2D) semiconducting material harbors intrinsic defects that can be harnessed to achieve tuneable electronic, optoelectronic, and electrochemical devices. However, achieving precise control over defect formation within monolayer MoS2, remains a notable challenge. Here, an in‐situ defect engineering approach for monolayer MoS2 using a pressure‐dependent chemical vapor deposition (CVD) process is presented. Monolayer MoS2 grown in a low pressure CVD conditions (LP‐MoS2) produces sulfur vacancy (Vs) induced defect‐rich crystals primarily attributed to the oxygen‐deficient growth conditions. Conversely, atmospheric pressure CVD‐grown MoS2 (AP‐MoS2) passivates these defects with oxygen from ambient conditions. This disparity in defect profiles profoundly impacts crucial functional properties and device performance. AP‐MoS2 shows a drastically enhanced photoluminescence, which is significantly quenched in LP‐MoS2 attributed to in‐gap electron donor states induced by the Vs defects. However, the n‐doping induced in LP‐MoS2 generates enhanced photoresponsivity and detectivity in fabricated photodetectors compared to the AP‐MoS2‐based devices. Defect‐rich LP‐MoS2 outperforms AP‐MoS2 as channel layers of field‐effect transistors (FETs), as well as electrocatalytic material for hydrogen evolution reaction (HER). This work presents a single‐step CVD approach for in situ defect engineering in monolayer MoS2 and presents a pathway to control defects in other monolayer 2D materials.