Structure of Ge(113): Origin and stability of surface self-interstitials

Using atomic-resolution scanning tunneling microscopy and first-principles calculations we show that Ge and Si(113) are structurally similar, contrary to previous reports. Both surfaces have (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. Statistical analysis of fluctuations observed between the two structures on Ge, combined with calculations for bulk interstitials, indicate that the surface (not the bulk) is the likely source and sink of the surface self-interstitials for both materials. [S0031-9007(98)07858-2].