Stabilization of the π-bonded 2 x 1 reconstruction and the adatom-like structure, that appeared during the crystallization of vacuum-deposited amorphous overlayers on clean (111)-(7 x 7) surfaces, was investigated by means of scanning tunnelling microscopy. The structure was seen on the surface only for initial amorphous Si thicknesses of 2 to 4 monolayers, and after annealing at 350 to 500C. An atomic model of the structure was proposed on the basis of high-resolution dual-bias scanning tunnelling microscope images. Because the adatom-like structure was formed on the dimer row of the substrate 7 x 7 reconstruction, the buried dimer stacking fault network and high surface atom density play essential roles in the stabilization of the structure.

Formation of π-bond chains on solid-phase homoepitaxially grown Si(111) surfaces T.Fukuda: Physical Review B, 1999, 59[15], 9752-5