Real-Time Imaging of K Atoms on Graphite: Interactions and Diffusion
J Renard and MB Lundeberg and JA Folk and Y Pennec, PHYSICAL REVIEW LETTERS, 106, 156101 (2011).
Scanning tunneling microscopy (STM) at liquid helium temperature is used to image potassium adsorbed on graphite at low coverage (approximate to 0.02 monolayer). Single atoms appear as protrusions on STM topographs. A statistical analysis of the position of the atoms demonstrates repulsion between adsorbates, which is quantified by comparison with molecular dynamics simulations. This gives access to the dipole moment of a single adsorbate, found to be 10.5 +/- 1 D. Time-lapse imaging shows that long- range order is broken by thermally activated diffusion, with a 30 meV barrier to hopping between graphite lattice sites.
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