Tuning the threshold voltage from depletion to enhancement mode in a multilayer MoS2 transistor via oxygen adsorption and desorption

Abstract

Selective chemical doping in two-dimensional (2D) molybdenum disulfide (MoS₂) is attractive for tailoring electrical properties according to device requirements. However, the ultra-thin 2D nature of MoS₂ makes it difficult to realize effective doping by conventional ion implantation. Here, a simple method based on low-temperature (150 °C) annealing in air is developed for effective chemical doping in MoS₂. We have demonstrated that the threshold voltage (V_th) of multilayer MoS₂ FET can be effectively tuned from depletion mode (V_th = −1.8 V) to enhancement mode (V_th = 1.1 V) by annealing in air at 150 °C. An energy band model based on electron trapping/detrapping due to oxygen adsorption on the MoS₂ surface is proposed to explain the underlying mechanism. The model is consistent with an oxygen adsorption–desorption process evidenced by vacuum annealing that recovers the V_th to its original value. These results can provide a simple approach for V_th engineering and make a significant step toward 2D nanoelectronic device applications.