Effect of biaxial tensile-compressive deformation on the optoelectronic properties of monolayers of MoTe2 with adsorbed alkali metals X (X = Li, Na, K, Rb, Cs): a first principles

Abstract

Based on a first-principles approach, the effects of tensile-compression deformation on the structural stability, electronic structure, and optical properties of monolayers of MoTe2 adsorbed with alkali metal atoms X (X = Li, Na, K, Rb or Cs) were calculated. It was found that the structural stability of the MoTe2 monolayer after adsorption of Li atoms was the most stable, with the smallest adsorption and formation energies and the smallest adsorption height. The movement of the Fermi energy toward the conduction band makes the system an n-type semiconductor. Subsequently, the adsorbed Li-MoTe2 monolayers were selected for tensile-compressive deformation, and with the increase of tensile deformation, the band gap decreased to zero at 10% deformation and exhibited metallic properties. As compressive deformation grows, the band gap shifts from direct to indirect, and metallic characteristics emerge when deformation approaches −10%. The Te-s and Te-p orbital electrons near the Fermi energy level and Mo-d orbitals make the main contribution to the adsorbed alkali metal molybdenum ditelluride system. In terms of optical characteristics, the MoTe2 system after alkali metal adsorption deformation is blue-shifted/ red-shifted at the absorption/reflection peak. These discoveries may help to broaden the possible applications of MoTe2 in low-dimensional electron-emitting devices.