One- and two-dimensional diffusion of metal atoms in graphene

Individual Au and Pt atoms in layers consisting of one or two graphene planes have been monitored in real time at high temperature by high-resolution TEM. The material was synthesized in an arc discharge and consisted of multi-walled nanotubes, onion-like graphitic nanoparticles, and some more or less isolated graphenic sheets. metal atoms replace carbon atoms and are located in single or multiple vacancies. Metal atoms with considerable off-plane positions can be excluded. Several images were recorded with the viewing direction along the layers, that is, where the layers are locally aligned parallel to the electron beam. The migration of Au or Pt atoms was also studied in multi-walled carbon nanotubes, from which the measured migration distances within certain time intervals for the diffusion coefficients could be derived.