Importance of Many-Body Dispersion in the Stability of Vacancies and Antisites in Free-Standing Monolayer of MoS₂ from First-Principles Approaches

Defects in MoS2 monolayer play a vital role in altering the electric and optical properties, which is a crucial factor in various semiconducting and optoelectronic devices. In the present work, we have investigated the thermodynamic stability of point defects in MoS2 monolayer by means of first-principles-based density functional theory (DFT) and ab initio atomistic thermodynamics. We have considered three vacancies and five antisites in our system, viz., Mo vacancy (VMo), SMo antisite, S2Mo antisite, S vacancy (VS), MoS antisite, S2 vacancy (VS2), MoS2 antisite, and 2MoS2 antisite. Our approach includes (i) the two-body van der Waals interaction under Tkatchenko–Scheffler scheme and (ii) many-body dispersion to account the effect of polarization on the defects’ stability. The many-body dispersion has posed a significant change in the pattern of stable defects. Hence, we report the stable defect states as observed by hybrid DFT with many-body dispersion as VS–2, VMo–2, and SMo–2 in n-type MoS2 monolayer and VS+2, VMo+2, and S2Mo+2 in p-type MoS2 monolayer. Among these stable defect states, SMo–2 and S2Mo+2 states have tuned the band gap of MoS2 monolayer in the range of 1.1–1.8 eV. Therefore, their optical response in comparison to pristine has inferred their applicability in photovoltaics. Finally, we obtain that these defects have significant concentration in the finite temperature range of 50–1000 K. Our results, therefore, predict the p-type defect states in MoS2 monolayer that would be helpful in device fabrications.