Character of defect states in vacancy-doped MoTe2 monolayer: Spatial localization, flat bands and hybridization gap

The structural and electronic properties of vacancy-doped 1H and 1T' MoTe2 monolayers are systematically investigated based on first-principles calculations. Te vacancy is found energetically favored over Mo vacancy for both phases, and Te double vacancy is more favored as it is formed by missing two Te atoms from opposite sides. Vacancy induced defect states are strongly spatially localized on the atoms within two or three shell surrounding the point defect. This strongly localized nature leads to weak dependence of the defect formation energy on defect concentrations, sharply peaked density of states, and flat bands. Moreover, the calculation suggests that Te vacancy opens a band gap in the 1T' MoTe2 monolayer, which can be tuned by lattice strain or external force. These results might give a guidance for the research on the application of MoTe2 in electronics and optoelectronics.