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Stability and dopability of native defects and group-V and -VII impurities in single-layer MoS2

We investigate the native defects, the Mo substitutional impurities of the group-VB and -VIIB elements, and the S substitutional impurities of the group-VA and -VIIA elements in single-layer MoS2, through density-functional theory calculations. It is found that the S-vacancy (V_S) and S-interstitial (S_i) are low in formation energy, about ~1 eV, in Mo- and S-rich conditions, respectively, but the carrier doping ability of the V_S and S_i is found to be poor, as they are deep level defects. The V, Nb, and Ta (group-VB) and Re (group-VIIB) impurities are found to be easily incorporated in single-layer MoS2, as Mo substitutional defects, where the V, Nb, and Ta are shallow acceptors and the Re is the only shallow donor among the considered. The unintentional n-type doping in single-layer MoS2 exfoliated from the naturally grown MoS2 bulk materials is suggested to originate from the Re impurity.