Electrical Doping Effect of Vacancies on Monolayer MoS2

Abstract

Doping of transition-metal dichalcogenides (TMDCs) is an effective way to tune the Fermi level to facilitate the band engineering required for different types of devices. For TMDCs, a controversy abounds with regard to the doping role played by vacancy-type defects. Here, we report a detailed study based on first-principles calculations proposing that the native sulfur vacancies (VS) can significantly alter the electrical doping level in MoS2 and tune the material to exhibit conventional n- or p-type semiconductor characteristics. In particular, we reveal that the lower concentration of the single VS (2.8 and 6.3%) yields p-type characteristics, whereas the higher concentration of the single VS or a cluster of VS (12.5, 18.8, and 25.0%) yields n-type characteristics. The trend is consistent with previous X-ray photoelectron spectroscopy and scanning tunneling microscopy results. Employing this method of tuning the electron doping level, we modeled a commonly used metal–semiconductor interface to demonstra...