Controlled Gas Molecules Doping of Monolayer MoS₂ via Atomic-Layer-Deposited Al₂O₃ Films

MoS₂ as atomically thin semiconductor is highly sensitive to ambient atmosphere (e.g., oxygen, moisture, etc.) in optical and electrical properties. Here we report a controlled gas molecules doping of monolayer MoS₂ via atomic-layer-deposited Al₂O₃ films. The deposited Al₂O₃ films, in the shape of nanospheres, can effectively control the contact areas between ambient atmosphere and MoS₂ that allows precise modulation of gas molecules doping. By analyzing photoluminescence (PL) emission spectra of MoS₂ with different thickness of Al₂O₃, the doped carrier concentration is estimated at ∼2.7 × 10¹³ cm^-2 based on the mass action model. Moreover, time-dependent PL measurements indicate an incremental stability of single layer MoS₂ as the thicknesses of Al₂O₃ capping layer increase. Effective control of gas molecules doping in monolayer MoS₂ provides us a valuable insight into the applications of MoS₂ based optical and electrical devices.