Nano Lett.http://dx.doi.org/10.1021/nl203224z (2011)

Progress in transmission electron microscopy (TEM) has achieved levels of precision where not only is it possible to image single atoms of light elements, but it is also possible to observe dynamic phenomena with the same spatial resolution. For example, Benedikt Westenfelder and colleagues have been able to observe what happens to hydrocarbon adsorbates on a graphene sheet when exposed to temperatures as high as 2,000 K. Current flowing through the graphene sheet was used to produce localised heat. Once a temperature of 300 K was reached the hydrocarbons were observed to form large layers of amorphous carbon. However, above 2,000 K, the amorphous carbon transformed into a polycrystalline graphene with a small grain size and a considerable number of free armchair edges. Aside from the importance for hydrocarbon transformation, the results demonstrate the power of low-energy TEM that could be extended to investigate other material systems.