First-principles investigation on electrical and adsorption properties of the ZnO/Silicene heterostructures: The role of Ag and N co-doping and external electric field

Abstract

ZnO monolayer, Ag doped ZnO (Ag-ZnO), N doped ZnO (N-ZnO), Ag and N co-doped ZnO monolayer (Ag/N-ZnO) are modeled using first principles based on density functional theory (DFT). The band gap of silicene (SiE) is modulated by constructing ZnO/SiE, Ag-ZnO/SiE, N-ZnO/SiE, and Ag/N-ZnO/SiE heterostructures and N-ZnO monolayer is the best nanosheet to open the band gap of SiE, which increases by about 160 times. Ag/N-ZnO/SiE exhibits metallic properties to promote charge transfer between Ag/N-ZnO ML and SiE. In addition, electrical structures and adsorption properties of the heterostructure under external electric field are investigated. Results indicate that the external electric field regulates the band gap of the heterostructures, but also leads to semiconductor–metal transition. The reduced work function (WF) of the heterojunctions shows the possibility of application in gas sensing. For NO and NO2 molecules, Ag/N-ZnO/SiE shows the maximum adsorption energy (Ead) of −3.81 eV and −4.72 eV, respectively. These results demonstrate that Ag/N-ZnO can not only regulate the bandgap of SiE by constructing heterojunctions, but also has potential applications in nitrogen oxides gas sensors.