Influence of mono- and bi-vacancy doped alkaline-earth metals on the optoelectronic properties of monolayer defective state MoTe2: A first-principles study

The effects of single-vacancy and double-vacancy doping with alkaline-earth metals on the stability, electronic structure, charge transfer, and optical properties of molybdenum ditelluride in the monolayer defective state (MoTe₂) have been investigated using first-principles methods. It is found that the structure of the molybdenum ditelluride system is more stable after double Te vacancies, with direct band-gap to indirect band-gap transitions occurring in single Te vacancies and Mo vacancies, and semiconductor to quasi-metal transitions occurring in double Mo vacancies. The binding energy in the defect state system of molybdenum ditelluride after vacancy defects is always negative, and the structure remains stable. In this paper, the most stable double Te vacancy state was selected for substitutional doping with alkaline-earth metals, and the Be atoms were doped with the largest amount of morphology, and Ca atoms were doped with the most pronounced decrease in band gap value. The direct band-gap semiconductor is maintained after doping with Be atoms. Doping with Mg, Sr and Ba changes the band-gap from direct to indirect. The double Te defect state MoTe₂ doped with Ca atoms has a tendency to transition to a quasi-metal. Regarding photoelectric properties, the system is blue-shifted on both the absorption and reflection peaks.