First principles studies on the electronic and contact properties of single layer 2H-MoS₂/1T'-MX₂ heterojunctions

Constructed via in-plane heterojunction contacts between the semiconducting 2H phase (as the channel) and the metallic 1T' phase (as the electrode), two-dimensional (2D) transition metal dichalcogenide (TMD) field-effect transistors (FETs) have received much recent attention because they significantly reduce contact resistance. In this paper, ab initio quantum transport simulation is done to study and predict the electronic states and contact properties of the 2H-MoS₂/1T'-MX₂ (WS₂, TaSe₂, NbSe₂, MoSe₂, TaS₂, and NbS₂) in-plane heterojunctions. It is found that the interfacial states are not obvious and the fluctuation of the average electron density at the 1T'/2H phase boundary is small for all 2H-MoS₂/1T'-MX₂ heterojunctions. The average electrostatic potential differences (ΔV) are all negative, which is beneficial to promote the charge transfer from 1T'-MX₂ to 2H-MoS₂. Moreover, the p-type Schottky contact of the 2H-MoS₂/1T'-MX₂ heterojunctions is formed and the Φ_SB,P values are 0.609 eV, 0.625 eV, 0.641 eV, 0.617 eV, 0.469 eV and 0.477 eV for 1T'-WS₂, 1T'-TaSe₂, 1T'-NbSe₂, 1T'-MoSe₂, 1T'-TaS₂, and 1T'-NbS₂, respectively. The results provide theoretical guidance for designing two-dimensional material devices.