First-principles study of electronic and sodium-ion transport properties of transition-metal dichalcogenides

Two-dimensional (2D) layered materials such as transition-metal dichalcogenides TS2(1-m)X2m (T = Mo, W; X = Se, Te) are available in mono and bilayers forms. The Rashba spin splitting is induced by the breaking of inversion symmetry in monolayer. The electronic structure of TS2(1-m)X2m is sensitive to an applied electric field. The perpendicular electric field can tune the energy gap. The semiconductor-metal transition appears under the critical electric field in the MoSSe/WSSe heterobilayer, and MoSTe/WSTe heterobilayer exhibits metal character due to spin-orbit coupling. Moreover, the results show that during sodiation/desodiation processes single-phase transition occurs with one one-dimensional (1D) transportation paths of sodium ions in MoS2, suggesting fast diffusion. Our results provide important insights into a wide range of applications of spin-polarized semiconductors and energy storage for transition-metal dichalcogenides TS2(1-m)X2m.