Missing-atom defects on these dichalcogenides were studied by using the projector augmented-wave method, based upon density functional theory. It was found that the presence of vacancies resulted in localized electronic states in the surface band-gap. These could affect scanning tunnelling microscopic images. On the basis of the results, it was suggested that hole and trimer defects could be attributed to single missing chalcogen, and single missing metal atom defects, respectively. The chalcogen vacancy systems behaved in a similar manner in both materials. However, MoTe2 with a metal vacancy constituted a Jahn-Teller system, whereas the equivalent MoS2 system did not.

J.C.Caulfield, A.J.Fisher: Journal of Physics - Condensed Matter, 1997, 9[18], 3671-86