Vacancy localization effects on MX2 transition-metal dichalcogenides: A systematic ab initio study

Two-dimensional transition-metal dichalcogenide (MX2) vacancy formation energetics are extensively investigated. Within an ab initio approach, we study the MX2 systems, with M = Mo, W, Ni, Pd, and Pt, and X = S, Se, and Te. Here we classify that chalcogen vacancies are always energetically favorable over the transition-metal ones. However, for late transition metals Pd 4d, and Pt 5d the metal vacancies are experimentally achievable, bringing up localized magnetic moments within the semiconducting matrix. By quantifying the localization of the chalcogen vacancy states we show that it rules the intra- and intervacancy interactions that establish both the number of vacancy states neatly lying within the semiconducting gap, as well as its electronic dispersion and spin-orbit coupling splitting. Combining different vacancies and phase variability 1T and 1H of the explored systems allows us to construct a guiding picture of the vacancy state localization.

Automated summary

This study extensively investigates the energetics of vacancy formation in two-dimensional transition-metal dichalcogenides (MX2). It is found that chalcogen vacancies are always energetically favorable, but metal vacancies in late transition metals such as Pd and Pt can be experimentally achieved and introduce localized magnetic moments. The localization of the chalcogen vacancy states determines the intra- and intervacancy interactions, as well as the number, electronic dispersion, and spin-orbit coupling splitting of vacancy states within the semiconducting gap.