Healing Donor Defect States in CVD-Grown MoS₂ Field-Effect Transistors Using Oxygen Plasma with a Channel-Protecting...

Molybdenum disulfide (MoS₂ ), a metal dichalcogenide, is a promising channel material for highly integrated scalable transistors. However, intrinsic donor defect states, such as sulfur vacancies (V_s ), can degrade the channel properties and lead to undesired n-doping. A method for healing the donor defect states in monolayer MoS₂ is proposed using oxygen plasma, with an aluminum oxide (Al₂ O₃ ) barrier layer that protects the MoS₂ channel from damage by plasma treatment. Successful healing of donor defect states in MoS₂ by oxygen atoms, even in the presence of an Al₂ O₃ barrier layer, is confirmed by X-ray photoelectron spectroscopy, photoluminescence, and Raman spectroscopy. Despite the decrease in 2D sheet carrier concentration (Δn_2D = -3.82×10¹² cm^-2 ), the proposed approach increases the on-current and mobility by 18% and 44% under optimal conditions, respectively. Metal-insulator transition occurs at electron concentrations of 5.7×10¹² cm^-2 and reflects improved channel quality. Finally, the activation energy (E_a ) reduces at all the gate voltages (V_G ) owing to a decrease in V_s , which act as a localized state after the oxygen plasma treatment. This study demonstrates the feasibility of plasma-assisted healing of defects in 2D materials and electrical property enhancement and paves the way for the development of next-generation electronic devices.