Scanning tunnelling microscopy was used to study the temperature and coverage dependences of the structure of Pb on the (111)Si 7 x 7 surface. It was found that, at low coverages, the Pb atoms favored faulted sites. The ratio of the numbers of Pb atoms on faulted and unfaulted sites increased during annealing. An energy difference of 0.05eV was estimated to be associated with a Pb atom on these 2 types of site. Mobility of Pb atoms on (111)Si was observed at temperatures which were as low as 260C, at coverages of 0.1 or 1 monolayer.

D.Tang, H.E.Elsayed-Ali, J.Wendelken, J.Xu: Physical Review B, 1995, 52[3], 1481-4