Scanning tunnelling microscopic measurements and  ab initio  calculations were performed with regard to the (113) surface. This surface was of interest because Ge islands on Si(001) or Si(111) exhibited (113) facets. Also, Si(113) was thermally stable in spite of its high Miller index, and had the properties which were required of a good substrate. Attention was drawn to the peculiar atomic structure of Si(113), which contained a novel structural unit that was built around a sub-surface interstitial atom. Such interstitials could also be present at other surfaces, particularly at steps, and could play an important role in atomic diffusion in the sub-surface layer. It was found that the interstitials were 6-fold coordinated, and this unexpected result spoiled the simple picture of a reconstruction that was driven by the re-bonding of dangling bonds. The present calculations indicated that the interstitials were released when the surface dangling orbitals re-bonded. This could result from the adsorption of atomic H, or from epitaxial growth.

J.Dabrowski, H.J.Müssig, G.Wolff: Journal of Vacuum Science and Technology B, 1995, 13[4], 1597-601