Strain effects on the behavior of isolated and paired sulfur vacancy defects in monolayer MoS2

Abstract

We investigate the behavior of sulfur vacancy defects, the most abundant type of intrinsic defect in monolayer MoS2, using first-principles calculations based on density functional theory. We consider the dependence of the isolated defect formation energy on the charge state and on uniaxial tensile and compressive strain up to 5%. We also consider the possibility of defect clustering by examining the formation energies of pairs of vacancies at various relative positions, and their dependence on charge state and strain. We find that there is no driving force for vacancy clustering, independent of strain in the material. The barrier for diffusion of S vacancies is larger than 1.9 eV in both charged and neutral states regardless of the presence of other nearby vacancies. We conclude that the formation of extended defects from S vacancies in planar monolayer MoS2 is hindered both thermodynamically and kinetically.

Hydrogen adsorption on MoS2-surfaces: a DFT study on preferential sites and the effect of sulfur and hydrogen coverage

“…Even though the differences are rather small (−0.06 eV, −0.10 eV and −0.04 eV), already the observation that the energetic cost of forming divacancies is approximately equal to forming monovacancies can intuitively be regarded as rather surprising. Nevertheless, this behavior is in line with results reported by Le et al 63 as well as Sensoy et al 64 . In the latter work it is shown that the defect-induced lattice reorganization in the 2H-MoS 2 basal plane is very small and local, and that the interaction between isolated monovacancies is negligible.…”

Stability of direct band gap under mechanical strains for monolayer MoS2, MoSe2, WS2 and WSe2

“…In this work, we simulate the Young's modulus of monolayer TX 2 cells and investigate the band structures of hexagonal and orthorhombic monolayer TX 2 cells under a wide range of strain amplitudes in different directions using first-principles methods. This theoretical method has been used in many previous studies in TMDs [23][24][25][26][27]. Our aim is to theoretically explore the relationship between the Young's modulus and the width of the direct band gap region.…”

CoFFEE: Corrections For Formation Energy and Eigenvalues for charged defect simulations

“…In particular, the scheme proposed by Freysoldt, Neugebauer and Van de Walle (FNV) has gained a lot of popularity owing to its consistency in deriving accurate corrections for charged defects in numerous materials [26]. This scheme has been extended to low-dimensional systems as well, and shown to perform well [38,39,40,41,42,43,44]. However, a generalized correction scheme implementation that works with bulk as well as low-dimensional systems is absent in the various DFT packages, or as an independent package [45,46].…”