First-principles analysis of MoS2/Ti2C and MoS2/Ti2CY2(Y=Fand OH) all-2D semiconductor/metal contacts

Abstract

First-principles calculations are used to explore the geometry, bonding, and electronic properties of MoS${}_{2}$/Ti${}_{2}$C and MoS${}_{2}$/Ti${}_{2}$C${Y}_{2}$ ($Y$ $=$ F and OH) semiconductor/metal contacts. The structure of the interfaces is determined. Strong chemical bonds formed at the MoS${}_{2}$/Ti${}_{2}$C interface result in additional states next to the Fermi level, which extend over the three atomic layers of MoS${}_{2}$ and induce a metallic character. The interaction in MoS${}_{2}$/Ti${}_{2}$C${Y}_{2}$, on the other hand, is weak and not sensitive to the specific geometry, and the semiconducting nature thus is preserved. The energy level alignment implies weak and strong $n$-type doping of MoS${}_{2}$ in MoS${}_{2}$/Ti${}_{2}$CF${}_{2}$ and MoS${}_{2}$/Ti${}_{2}$C(OH)${}_{2}$, respectively. The corresponding $n$-type Schottky barrier heights are 0.85 and 0.26 eV. We show that the MoS${}_{2}$/Ti${}_{2}$CF${}_{2}$ interface is close to the Schottky limit. At the MoS${}_{2}$/Ti${}_{2}$C(OH)${}_{2}$ interface, we find that a strong dipole due to charge rearrangement induces the Schottky barrier. The present interfaces are well suited for application in all-two-dimensional devices.