The Interfacial Properties of Monolayer MX-Metal Contacts

Binary IV-VI chalcogenides MXs (SnS, SnSe, SnTe, GeS, GeSe, and GeTe), as a family two-dimensional (2D) semiconductor material, have a proper bandgap, high carrier mobility, stability in ambient conditions, and a pucker structure, hence they are potential channel materials for the next-generation electronic and optoelectronic devices. 2D MXs devices should directly contact the metal electrodes to inject suitable types of carriers, on account of the random dopant fluctuation. However, a Schottky contact is always formed at the interface, which degrades the performance of the MXs devices. Herein, we report the contact characteristics of the MXs field-effect transistors (FETs) with Graphene(Gr)/Ag/Au electrodes (two-interface model) by using quantum transport calculations and density functional theory. At the vertical interface, the MXs FETs form Van der Waals (vdW) contact type after being contacted with the Gr electrode, and an Ohmic contact is formed after being contacted with Ag and Au electrodes. At the lateral interface, the SnTe (armchair and zigzag), GeS (zigzag), and GeSe (zigzag) FETs with Gr electrode get a desired p-type Ohmic contact or quasi p-type Ohmic contact, suggestive of high device performance in such an MXs device. Our simulation provides a theoretical foundation for the choice of suitable electrodes in future ML MXs devices.