Point defects in the 1T' and 2H phases of single-layer MoS_2: A comparative first-principles study

摘要

The metastable 1T' phase of layered transition metal dichalcogenides has recently attracted considerable interest due to electronic properties, possible topological 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'-MoS_2) 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 analyze their atomic structure, thermodynamic stability, and electronic and magnetic properties. The emerging picture suggests that, under thermodynamic equilibrium, 1T'-MoS_2 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'-MoS_2 are very likely to occur while Mo adatoms and antisites induce local magnetic moments. Contrary to the 2H phase, Mo vacancies in 1T'-MoS_2 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'-MoS_2 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.