Electronic and magnetic properties of group-V TMDs monolayers with defects: A first-principles study

By adopting the first-principles methods based on the density functional theory, we studied the electronic and magnetic properties of group-V MX₂ (M = V, Nb, Ta; X = S, Se, Te) monolayers with atomic-sized structural defects. We firstly studied the two phases of 1H and 1T. It shows that the formation energies of the 1T phase are lower compared with those of the 1H phase for VSe₂ and VTe₂. For the rest MX₂, the formation energies of the 1H phase are lower. Our results indicate that all the 1H and 1T phases of MX₂ are metal except for 1H-VSe₂ and 1H-VTe₂ which are semiconducting. For monolayers MX₂ with atomic-sized defects, our calculations predict that the diatomic X atoms vacancies of V_X-X and V_2X both cause the metal–semiconductor transition, and vacancies of V_M and V_X-X, as well as anti-site defect of M_X induce semiconductor–metal transition. Meanwhile, the total magnetic moments of the 1H and 1T phases of VX₂ increase with inducing the X atom vacancies including V_X, V_X-X and V_2X. Additionally, V_X vacancy and V_2X vacancy bring magnetism into the 1T-TaSe₂ and 1T-TaS₂, respectively.