Stability of metallic edges and Fermi-level pinning in transition-metal dichalcogenide nanoribbons

TL;DR

This study uses first-principles calculations to analyze the stability and electronic properties of transition-metal dichalcogenide nanoribbons, revealing persistent metallic edge states and Fermi-level pinning influenced by edge reconstruction and chalcogen chemical potential.

Contribution

It provides new insights into the stability and electronic structure of TMD nanoribbons with reconstructed edges containing chalcogen adatoms.

Findings

Metallic edge states are present in all studied nanoribbons.

Edge reconstruction with chalcogen adatoms is energetically favorable.

Fermi level of edge metallic phase is lower than that of the bulk 2D material.

Abstract

Nanoribbons of MoS$_2$ present a unique electronic structure that consists of a semiconducting bulk bounded by metallic edges; same holds for other Transition-Metal Dichalcogenides (TMDs) (Mo-,W-,S$_{2}$,Se$_{2}$). We perform first-principles calculations for TMD nanoribbons with reconstructed zig-zag metal terminated edges that contain chalcogen adatoms. All nanorobbons have possitive edge energies when the chemical potential of chalcogens is close to the energy of solids, and negative edge energies for high chemical potential. The reconstruction with two chalcogen adatoms is expected to be the most stable one. In all nanoribbons, a metallic phase is found near their edges, with the Fermi level of this metallic phase being lower than the Fermi level of the 2D material.