DFT exploration of sensor performances of two-dimensional WO3 to ten small gases in terms of work function and band gap changes and I-V responses

A combination of density functional theory (DFT) and nonequilibrium Green function (NEGF) based simulation was employed to investigate the prospects of two-dimensional (2D) WO3 materials for gas sensing applications. The target gas molecules considered are O2, N2, NH3, NO, CO, CO2, CH4, C2H6, HCHO, and H2S. Our computed binding energies suggested that the interactions between the gas molecules and 2D WO3 nano-layers cleaved from (0 0 1) plane of WO3 bulk crystal are stronger than those with some other 2D materials like graphene and borophene. The electronic properties of adsorption systems such as band gaps, work functions and partial density of states were calculated and compared to the bare substrates. The results demonstrate high sensitivity and selectivity of the 2D WO3 nano-layers towards NH3, NO, HCHO, O2 and H2S. The computation of transport properties such as transmission functions and current-voltage (I-V) characteristics indicated that the presence and absence of gas molecules on the 2D WO3 nano-layers can well realize the electronic device characteristics (ON and OFF) of gas sensors. Theoretical recovery times were also calculated to estimate the reusability of the 2D WO3 nano-layers based gas sensors. Our results suggest that the 2D WO3 nano-layers are promising candidates for sensing applications to NH3, NO, HCHO, O2 and H2S, better than graphene and borophene.