Monomers of Si were observed in empty-state scanning tunnelling microscopic images at temperatures between ambient and 115C. The monomers were trapped at the ends of re-bonded SB-type dimer rows. When the monomers escaped thermally from the traps, they rapidly diffused along the substrate dimer row until they either found another unoccupied trap, or returned to their original trap. It was deduced that the binding activation barrier at isolated traps was about 1.0eV. It was noted that a slightly lower barrier existed for the hopping of monomers between the ends of neighboring dimer rows. This process facilitated diffusion along segments of SB-type steps.

B.S.Swartzentruber: Physical Review B, 1997, 55[3], 1322-5