High-Resolution Scanning Tunneling Microscopy Imaging of Mesoscopic Graphene Sheets on an Insulating Surface

TL;DR

This paper demonstrates high-resolution STM imaging of single-layer and few-layer graphene on silicon dioxide, revealing the honeycomb structure and differences from bulk graphite, indicating high-quality monolayer samples.

Contribution

First high-resolution STM images of single-layer graphene on an insulating surface, showing atomic structure and defect absence.

Findings

Single-layer graphene exhibits honeycomb atomic structure in STM images.

Few-layer graphene shows surface symmetry similar to bulk graphite.

High-quality, defect-free monolayer graphene was achieved.

Abstract

We present scanning tunneling microscopy (STM) images of single-layer graphene crystals examined under ultrahigh vacuum conditions. The samples, with lateral dimensions on the micron scale, were prepared on a silicon dioxide surface by direct exfoliation of single crystal graphite. The single-layer films were identified using Raman spectroscopy. Topographic images of single-layer samples display the honeycomb structure expected for the full hexagonal symmetry of an isolated graphene monolayer. The absence of observable defects in the STM images is indicative of the high quality of these films. Crystals comprised of a few layers of graphene were also examined. They exhibited dramatically different STM topography, displaying the reduced three-fold symmetry characteristic of the surface of bulk graphite.