Direct Imaging of Graphene Edges: Atomic Structure and Electronic Scattering

TL;DR

This study uses atomic-resolution STM to analyze graphene edges, revealing atomic-scale zigzag and armchair orientations and associated electronic scattering patterns, advancing understanding of edge-related electronic properties.

Contribution

It provides the first detailed atomic-scale imaging of graphene edges and correlates edge structure with electronic scattering phenomena.

Findings

Most edges are zigzag-oriented with atomic roughness.

Standing wave patterns are observed near armchair edges.

Electronic backscattering occurs at armchair edges but not zigzag edges.

Abstract

We report an atomically-resolved scanning tunneling microscopy (STM) investigation of the edges of graphene grains synthesized on Cu foils by chemical vapor deposition (CVD). Most of the edges are macroscopically parallel to the zigzag directions of graphene lattice. These edges have microscopic roughness that is found to also follow zigzag directions at atomic scale, displaying many ~120 degree turns. A prominent standing wave pattern with periodicity ~3a/4 (a being the graphene lattice constant) is observed near a rare-occurring armchair-oriented edge. Observed features of this wave pattern are consistent with the electronic intervalley backscattering predicted to occur at armchair edges but not at zigzag edges.