The positions of Ge atoms intermixed into the Si(100) surface at very low concentrations were identified by using empty-state imaging in scanning tunnelling microscopy. A measurable degree of place exchange occurred at temperatures as low as 330K. Contrary to previous conclusions, a good differentiation between Si atoms and Ge atoms could be achieved by using proper imaging conditions.

Scanning Tunnelling Microscopy Identification of Atomic-Scale Intermixing on Si(100) at Submonolayer Ge Coverages X.R.Qin, B.S.Swartzentruber, M.G.Lagally: Physical Review Letters, 2000, 84[20], 4645-8