First-principles investigation on the interface of transition metal dichalcogenide MX₂ (M = Mo, W; X = S, Se) monolayer on Al₂O₃(0 0 0 1)

By performing first-principles calculation, we studied the interface of transition metal dichalcogenides MX₂ (M = Mo, W; X = S, Se) monolayer on Al₂O₃(0 0 0 1) substrate for applications in field effect transistor. We firstly examined the 1H, 1T and ZT phases of MX₂ monolayers and found that the 1H structure is the best channel material among the three polytypes of MX₂. 1H MX₂ on both the Al and O terminated Al₂O₃(0 0 0 1) substrate are energetically favorable. Systems of MX₂ on Al-terminated Al₂O₃(0 0 0 1) substrate have larger band gaps than the counterpart of O-terminated Al₂O₃(0 0 0 1) substrate. More importantly, WS₂ on Al-terminated Al₂O₃(0 0 0 1) substrate is the most stable one and has a direct band gap of 1.79 eV. Furthermore, we investigated the effect of intrinsic defects on the electronic properties of WS₂/Al₂O₃(0 0 0 1) interface. Our calculation results show that Al, W, S vacancy exhibit p-type doping and n-type doping is obtained for O vacancy, and all of these vacancy defects induce defect states in the band gap for both the Al terminated and O terminated WS₂/Al₂O₃ systems.