ELECTRONIC-STRUCTURE AND SCANNING TUNNELING MICROSCOPE IMAGES OF MISSING-ATOM DEFECTS ON MOS2 AND MOTE2 SURFACES

Missing-atom defects on the transition metal dichalcogenides MoS2 and MoTe2 have been studied using the projector augmented-wave method, bas ed on ab initio density functional theory. The presence of the vacanci es results in localized electronic states in the surface band gap whic h can affect the STM image, and on the basis of our results we believe that the hole and trimer defects such as those observed by Fuchs et a l could be explained by single-missing-chalcogen and single-missing-me tal-atom defects respectively. It is found that the chalcogen vacancy systems behave in a similar way for both MoS2 and MoTe2; however, the system of MoTe2 with a metal vacancy is discovered to be a Jahn-Teller system, while the equivalent MoS2 system is not. The effects that thi s has on the atomic and electronic structure and the STM images are di scussed.