Defects-/doping-driven modulation of the electronic and magnetic properties of 2H- and Td-phase WTe2 monolayers: A first-principle study

As one of the transition metal dichalcogenides (TMDs) with layered structure, tungsten telluride (WTe2) has been known for its excellent electric and magnetic properties. Here, we applied density functional theory (DFT) to modify and simulate the structures of 2H-phase and Td-phase WTe2 using the first-principle calculations, and systematically investigated the impact of vacancy defects and substitutional doping on the electronic properties of them. Different types of point defect structures were constructed and their stability was proved by formation energy. Both of single and double vacancy defects are considered, and it shows that 2H-VW translates from semiconducting to semi-metallic, while 2H-VTe and 2H-V2Te remain direct band-gap and indirect band-gap semiconductors, respectively. Td-VTe induces spin polarization and Td-VW changes from semi-metallic to semiconductor. For substitutional dopants, the W or Te atom in 2H-phase and Td-phase WTe2 are substituted by Al, B, C, Co, Fe, N, P, Si atoms. The results show that, except for 2H-C and 2H-Si, all the doping systems of 2H-phase have obvious spin polarization and turn to be magnetic semiconductors. But these doped atoms hardly induce spin polarization in Td-phase WTe2 for the spin-up and spin-down states are mostly symmetrical in the density of state. This work is expected to play a positive role in understanding and regulating the properties of WTe2 and accelerating future applications of nanomaterials.