By using atomic-resolution scanning tunnelling microscopy and first-principles calculations, it was shown that Ge and Si(113) were structurally similar. Both surfaces had (3 x 2) and (3 x 1) reconstructions; stabilized by surface self-interstitials, with the ( 3 x 2) lower in energy on Si but degenerate with the (3 x 1) on Ge. The statistical analysis of fluctuations observed between the two structures on Ge, combined with calculations for bulk interstitials, indicated that the surface rather than the bulk was the probable source and sink of the surface self-interstitials in both materials.

Structure of Ge(113) - Origin and Stability of Surface Self-Interstitials. A.Laracuente, S.C.Erwin, L.J.Whitman: Physical Review Letters, 1998, 81, 5177-80