Performance prediction of 2D vertically stacked MoS2-WS2 heterostructures base on first-principles theory and Pearson correlation coefficient

The gas sensor made of two-dimensional (2D) material heterojunction has superior gas sensitivity, but the response mechanism has not been systematically investigated for a long time. In this work, the changes in total density of states (TDOS), partial density of states (PDOS), band gap (BG), and differential charge density (DCD) are investigated by first-principles calculations, revealing the response mechanism of NO2 adsorption by V-MoS2-WS2. The theoretical response value and recovery time of the sensor are described by the Boltzmann transport theory. The theoretical response recovery time and response value are analyzed by Pearson correlation coefficient, and the main influencing factors are BG and electron transfer. Through bader charge analysis, it is found that the electron transfer in the response process of the gas sensor is not only the transfer between the material surface and gas but also that the internal metal atoms provide electrons to be transferred to the gas molecules through the non-metal atoms. This discovery effectively explains the transient and steady-state processes of sensor response, fills the gap in the response mechanism of gas sensors prepared by 2D material heterojunction, and lays the theoretical foundation for the development of 2D material heterojunction gas sensors.