Hopping transfer optimizes avalanche multiplication in molybdenum disulfide

Abstract

Recently, avalanche multiplication has been observed in TMDC-based FETs, enhancing sensor performance with high sensitivity. However, the high voltage required for operation can damage the FETs, making it crucial to reduce the breakdown voltage for effective sensing applications. Here, we demonstrate that the utilization of hopping transfer induced by high-density defects can effectively reduce the breakdown voltage in TMDCs FETs. By substituting oxygen atoms for sulfur atoms in a monolayer of MoS₂, we create MoS_2-xO_x, with x carefully adjusted within the range of 0–0.51. Oxygen doping reduces the bandgap of TMDCs and enhances ion collision rates. Moreover, higher levels of oxygen doping (x > 0.41) in MoS_2-xO_x exhibit nearest-neighbor hopping behavior, leading to a significant enhancement in electron mobility. These improvements result in a decrease in the breakdown voltage of avalanche multiplication from 26.2 V to 12.6 V. Additionally, we propose avalanche multiplication in MoS_2-xO_x as an efficient sensing mechanism to overcome the limitations of gas sensing. The MoS_2-xO_x sensors display an ultra-high response to NO₂ gas in the air, with a response of 5.8 × 10³ % to NO₂ gas of 50 ppb at room temperature, which is nearly two orders of magnitude higher than resistance-type gas detectors based on TMDCs. This work demonstrates that hopping transfer induced by high-density oxygen defects can effectively decrease the breakdown voltage of MoS_2-xO_x FETs, enhancing avalanche multiplication and serving as a promising mechanism for ultrasensitive gas detection.