Distinct Reconstruction Patterns and Spin-Resolved Electronic States along the Zigzag Edges of Transition Metal Dichalcogenides

TL;DR

This study uncovers new reconstruction patterns and distinct electronic and magnetic edge states in transition metal dichalcogenides, with implications for spintronics and catalysis, using first-principles calculations.

Contribution

It reveals a universal (2x1) edge reconstruction pattern on M edges and distinct electronic/magnetic properties of M and X edges in MX2 monolayers.

Findings

M edges exhibit a universal (2x1) reconstruction with self-passivation.

X edges show different reconstructions depending on the material.

Distinct electronic and magnetic properties found at M and X edges.

Abstract

Two-dimensional transition metal dichalcogenides represent an emerging class of materials exhibiting various intriguing properties, and integration of such materials for potential device applications will necessarily encounter creation of different boundaries. Using first-principles approaches, here we investigate the structural, electronic, and magnetic properties along two inequivalent zigzag M and X edges of MX$_{2}$ (M=Mo, W; X=S, Se). Along the M edges, we reveal a previously unrecognized but energetically strongly preferred (2x1) reconstruction pattern, which is universally operative for all the MX$_{2}$, characterized by a self-passivation mechanism through place exchanges of the outmost X and M edge atoms. In contrast, the X edges undergo a more moderate (2x1) or (3x1) reconstruction for MoX$_{2}$ or WX$_{2}$, respectively. We further use the prototypical zigzag MoX$_{2}$ nanoribbons to demonstrate that the M and X edges possess distinctly different electronic and magnetic properties, which are discussed for spintronic and catalytic applications.