Mesoscopic scale study of lateral dynamics of Sn intercalation of the graphene buffer layer on SiC

The dynamics of Sn intercalation of the buffer layer (BL) on SiC was investigated with a frozen-in diffusion front using Kelvin Probe Force Microscopy. The technique allows to laterally distinguish between intercalated regions and the pristine BL. Comparing topography features with the contact potential difference on the mesoscopic scale confirms a significantly higher diffusion barrier close to surface steps relative to the terrace. The results show a distinct locally confined mechanism for the material flow from terrace to terrace on the vicinal substrate surface. Nucleation and the formation of Sn intercalated phases occur preferentially at step edges. This results in a mesoscopic growth against the macroscopic diffusion direction.