Effect of Na atom adsorption on the electronic structure of F-doped modified MoTe2 systems in the presence of an electric field: first principles

Abstract

Abstract Abstract
The effect of electronic structure and charge transfer on the adsorption of alkali metal sodium atoms by halogen-fluorine atom doped molybdenum ditelluride (MoTe2) has been investigated using a first-principles approach. It was found that the molybdenum ditelluride system underwent a direct bandgap semiconductor-to-metal transition after doping with halogen fluorine atoms. Upon adsorption of alkali metal Na atoms, the conduction band of the F-MoTe2 system shifts from metal to direct bandgap semiconductor. This semiconductor-to-metal-to-semiconductor bandgap modulation method can be well applied to photovoltaics. In addition, we discuss three potential adsorption sites: the hollow site (H), the bridge site (B) and the top site (T). The results showed that all three adsorption sites could be stabilized for adsorption. Subsequently, we selected the most stable B site and applied an electric field ranging from -0.5 eV/Å to 0.5 eV/Å to the system. At an electric field strength of -0.5 eV/Å, the system transforms from a direct bandgap semiconductor to a metal. In terms of density of states, F-s, F-p, Te-s, Te-p, and Mo-d pass the Fermi energy level, increasing carrier concentration. It is hoped that these studies will play an important role in improving the photoelectric conversion efficiency.
Keywords: first principles; F doping; Na adsorption; applied electric field; electronic structure.