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

TL;DR

This study uses density-functional theory to analyze native defects and impurities in single-layer MoS2, revealing their formation energies, doping abilities, and implications for unintentional doping.

Contribution

It provides detailed insights into defect formation energies and dopability of native and impurity defects in single-layer MoS2, highlighting Re as a shallow donor.

Findings

V_S and S_i have low formation energies but poor doping ability.

Re acts as a shallow donor, explaining unintentional n-type doping.

V, Nb, Ta are shallow acceptors when substituting Mo.

Abstract

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.