Heterobilayer CaS/CaSe: A promising sensor for environmental toxic NO2 gas with high selectivity and sensitivity

A new hetero CaS/CaSe bilayer sensor for environmental toxic NO2 gas is reported with excellent adsorption energy, quick recovery time and large sensitivity. A total of sixteen possible locations for NO2 molecule are considered on both the CaS and CaSe surfaces of CaS/CaSe for investigation under density functional theory (DFT) and DFT-D2 method of Grimme. The dynamical stability of CaS/CaSe and spin-polarized band structure and density of states are calculated to understand the effect of NO2 adsorption on the CaS/CaSe surface. The charge transfer of between NO2 and CaS/CaSe surface is understood through charge density maps. The recovery time for desorption of NO2 molecules from the CaS/CaSe surface is also calculated for the developed sensor. In order to understand the performance of our developed sensor, electronic charge transport device is modeled and NO2 sensitivity is calculated under the non-equilibrium Green's function (NEGF) framework. The present work identifies two-dimensional hetero CaS/CaSe bilayer as an excellent sensor for environmental toxic NO2 gas molecule for future relevant applications.