Structure of Graphene

The structure of the synthetic graphene is studied primarily using atomic-resolution HRTEM imaging using state-of-the-art aberration-corrected machines. Most recently we have been part of the microscopy activities being undertaken using the Oxford-JEOL 2200MCO FEG-TEM in the Department of Materials. Monochromation of the electrons from the gun, combined with both probe and imaging CEOS spherical aberration correctors enable us to image graphene with resolution ~ 80 picometers. Fully resolved HRTEM images of single atoms in graphene are obtained.

We have revealed how few layer graphene sheets merge together, and strain that arises in distorted regions of few layer graphene from pinches in the film.

Our most recent activity has centered around defects, dislocations and disorder in monolayer graphene (see HRTEM image below).

We have also studied the dynamics of edge atoms in graphene, shown below. The edges of graphene are unique in that they are not fully bonded and therfore highly reactive with motion confined to 1D.

The image below is a series of images 10 seconds apart showing an extra atom arriving at the edge in triangular bonding form, then ejecting.

The image below shows a single atom edge, as well as bond breaking and reforming after 10 seconds of electron beam irradiation.

Stone-Wales bond rotations were captured at the edge. (10 s between images).

We study impurity atoms, such as Si, and their interaction with vacancies in graphene (See HRTEM movies below). Sequences of HRTEM images taken every 10 seconds can be compiled into a time-series that reveals dynamics. These movies show the dynamics of single Si atoms being trapped in mono and di vacancies in graphene.