Exploration of electrical contact type in two-dimensional WS2/Nb2CX2 (X = H, F, Cl) heterostructures

Seeking a proper electrode contact for two-dimensional transition-metal dichalcogenides is significant for ultrathin electronic devices. According to the first-principles computations and quantum transport simulations, the interfacial features of monolayer (ML) WS2 are systematically verified in contact with pristine and modified ML MXene (Nb2C/Nb2CH2/Nb2CF2/Nb2CCl2). Based on the computed tunneling and Schottky barriers in the vertical direction, these four systems can be classified into three types. The WS2/Nb2C system belongs to type-I, which represents significant interfacial coupling and serious metallization of WS2. The WS2/Nb2CH2 system belongs to type-II, in which the intermediate interfacial coupling and a few gap states are observed, forming quasi-Ohmic contact. The WS2/Nb2CX2 (X = F, Cl) systems belong to type-III, which exhibits weak interfacial interaction, forming n-type Schottky contact containing a barrier height of 0.60 eV and 0.17 eV for X = F and Cl, respectively. Furthermore, the quantum transport properties are simulated through constructing two-probe field-effect transistors models with MXene as electrodes. The n-type Schottky contacts are constructed for all systems in the lateral orientation. Our work provides an imperative understanding of the contact and transport features of ML WS2 and will improve the experimental construction of WS2-based electronic devices.