Point defects in the 1T′ and 2H phases of single-layer MoS2 : A comparative first-principles study

Abstract

The metastable 1T' phase of layered transition metal dichalcogenides has recently attracted considerable interest due to electronic properties, possible topological electronic phases and catalytic activity. We report a comprehensive theoretical investigation of intrinsic point defects in the 1T' crystalline phase of single-layer molybdenum disulfide (1T' -MoS2), and provide comparison to the well-studied semiconducting 2H phase. Based on density functional theory calculations, we explore a large number of configurations of vacancy, adatom and antisite defects and analyse their atomic structure, thermodynamic stability, electronic and magnetic properties. The emerging picture suggests that, under thermodynamic equilibrium, 1T' -MoS2 is more prone to hosting lattice imperfections than the 2H phase. More specifically, our findings reveal that the S atoms that are closer to the Mo atomic plane are the most reactive sites. Similarly to the 2H phase, S vacancies and adatoms in 1T' -MoS2 are very likely to occur while Mo adatoms and antisites induce local magnetic moments. Contrary to the 2H phase, Mo vacancies in 1T' -MoS2 are expected to be an abundant defect due to the structural relaxation that plays a major role in lowering the defect formation energy. Overall, our study predicts that the realization of high-quality flakes of 1T' -MoS2 should be carried out under very careful laboratory conditions but at the same time the facile defects introduction can be exploited to tailor physical and chemical properties of this polymorph. arXiv:1804.04575v1 [cond-mat.mtrl-sci]

Defect engineered MoSSe Janus monolayer as a promising two dimensional material for NO2 and NO gas sensing

“…The structural stability of the defect containing monolayers is defined using the formation energy as = − + ; where, and are the total energies for defect containing monolayer and pristine monolayer respectively, and is the total energy of the removed atom 40 26,41,44,45 . The similar observations are also noticed and reported based on the formation energy of chalcogen vacancy included TMDCs based monolayer [46][47][48] . The formation energy of chalcogen vacancy included monolayers is less than the other defects, that's why the observation of chalcogen vacancy defects is more common.…”

Molecular chemistry approaches for tuning the properties of two-dimensional transition metal dichalcogenides

“…69 Its defects and their influences on various physical properties have been extensively investigated, both experimentally [157][158][159][160][161][162][163][164][165][166][167] and theoretically. 165,[168][169][170][171][172][173][174] In comparison, a relatively smaller number of works have focused on other TMDs, and in particular MoWSeS materials. 172,[175][176][177][178][179][180] Vacancies are a common type of point defects in ultrathin TMD samples and have been found in multiple forms ─ e.g.…”

Charge density wave phase, Mottness, and ferromagnetism in monolayer 1T−NbSe2

“…The latter is, to the best of our understanding, responsible for the recurrent occurrence of CDWs in the 1T dichalcogenides and lead to stronger distortions when the filling is closer to half-filling, as e.g. in 1T -MoS 2 [47] or ReS 2 [48], in which strong metal-metal bonds are formed. The Fermi surface is typical of group V 1T dichalcogenides and displays pseudo-nesting, favouring density wave instabilities with incommensurate wave vectors Q i = Q ICDW b i , where b i (i = 1, 2, 3) are the three reciprocal lattice vectors of a triangular lattice and Q ICDW ≈ 0.25 − 0.33 [2,49], depending on materialdependent details of the electronic structure.…”