Design of MXene contacts for high-performance WS2 transistors

Abstract

Achieving low-resistance contact is crucial for enhancing the performances of nanoelectronic devices. To find high-performance WS2 transistors, we systematically investigated the interfacial properties of monolayer WS2 in contact with a series of MXenes (Ti2C, V2C, Cr2C, Zr2C, Hf3C2, and Ti3C2) using first-principles calculations. Analyses of the interface structure, effective potential, electron localization function, energy bands, and density of states of the MXene top contacts with monolayer WS2 indicated that Ti2C, Zr2C, Hf3C2, and Ti3C2 couple strongly with WS2, leading to the metallization of monolayer WS2 and the formation of ideal Ohmic contacts in the vertical direction. To further evaluate the performances of the WS2/MXene transistors, the quantum transport properties were simulated using the nonequilibrium Green’s function method. The results indicated that the WS2 transistors with Zr2C and Hf3C2 electrodes have small lateral Schottky barrier heights of 0 and 0.08 eV, respectively, implying the formation of Ohmic and quasi-Ohmic contacts in WS2/Zr2C and WS2/Hf3C2. It means that low-resistance contacts can be achieved at WS2/Zr2C and WS2/Hf3C2 systems, indicating that Zr2C and Hf3C2 are promising electrode for monolayer WS2 to form high-performance transistors. These findings provide vital insights for the design of high-performance nanoelectronic devices based on two-dimensional materials.