WS Transistors with Sulfur Atoms Being Replaced at the Interface: First-Principles Quantum-Transport Study.

Reducing the contact resistance is one of the major challenges in developing transistors based on two-dimensional materials. In this study, we perform first-principles quantum-transport calculations by adopting a novel type of partially sulfur-replaced edge contact metal/WSX/WS in order to lower the Schottky barrier height and in turn reduce the contact resistance. Here, the sulfur replacements produce a segment of the metamaterial WSX (X = P, As, F, and Cl), using group V or halogen atoms to substitute sulfur atoms on one side of a WS monolayer. We further compare the effects of such sulfur replacements on the interface metallization and bonding. Such WSX-buffered contacts exhibit contact resistances as low as 142 and 173 Ω·μm for the p-type Pt/WSP/WS and n-type Ti/WSCl/WS edge contacts, respectively. Moreover, ab initio molecular dynamics is employed to observe a stable standalone WSX monolayer at room temperature.