PNAS 106, 10103 (2009), doi:10.1073/pnas.0905193106, http://www.youtube.com/watch?v=dPJBalMZ824&feature=channel_page, http://www.nanowerk.com/news/newsid=11108.php
We induced sublimation of suspended few-layer graphene by in situ
Joule-heating inside a transmission electron microscope. The graphene
sublimation fronts consisted of mostly {1100} zigzag edges. Under
appropriate conditions, a fractal-like โcoastlineโ morphology was
observed. Extensive multiple-layer reconstructions at the graphene
edges led to the formation of unique carbon nanostructures, such as sp2-bonded
bilayer edges (BLEs) and nanotubes connected to BLEs. Flat
fullerenes/nanopods and nanotubes tunneling multiple layers of graphene
sheets were also observed. Remarkably, >99% of the graphene edges
observed during sublimation are BLEs rather than monolayer edges
(MLEs), indicating that BLEs are the stable edges in graphene at high
temperatures. We reproduced the โcoastlineโ sublimation morphologies by
kinetic Monte Carlo (kMC) simulations. The simulation revealed
geometrical and topological features unique to quasi-2-dimensional (2D)
graphene sublimation and reconstructions. These reconstructions were
enabled by bending, which cannot occur in first-order phase
transformations of 3D bulk materials. These results indicate that
substrate of multiple-layer graphene can offer unique opportunities for
tailoring carbon-based nanostructures and engineering novel
nano-devices with complex topologies.