Using scanning tunnelling microscopy, direct observations were made of individual embedded Ge atom movement within the Si(100)-(2x1)-Ge surface at as low as 90C. It was demonstrated that the Ge atoms moved via exchange diffusion with adsorbed monomers and individual constituent atoms of adsorbed dimers. These observations were consistent with previous density-functional theory calculations, which predicted the atomistic pathways and energetic barriers for both exchange mechanisms. It was found that neither adsorbed monomers nor dimers could diffuse by more than a few nm between exchange events; thus illustrating how Ge diffusion and intermixing were closely coupled at the nanoscale on the Si(100) surface.

Ge Diffusion at the Si(100) Surface. E.Bussmann, B.S.Swartzentruber: Physical Review Letters, 2010, 104[12], 126101