MICROSCOPIC PICTURE OF SI(113) - A NOVEL SURFACE RECONSTRUCTION, THE ORIGIN OF DEFECTS, AND THE PROCESS OF ADSORPTION - THEORETICAL AND EXPERIMENTAL-STUDY

We report results of scanning tunneling microscope measurements and ab initio calculations for Si(113). This surface is of general interest: Ge islands on Si(001) and Si(111) have (113) facets, Si(113) is therm ally stable despite its high index, and it has properties of a good su bstrate. We bring into focus the peculiar atomic structure of Si(113) which contains a novel structural unit built around a subsurface inter stitial atom. Such interstitials may be present also at other surfaces , particularly at steps, and may play an important role in atomic diff usion in the subsurface layer. The interstitials are sixfold coordinat ed; this unexpected result disturbs the simple picture of reconstructi on driven by rebonding of dangling bonds. Our calculations indicate th at the interstitials are released when the surface dangling orbitals r ebond, e.g., as the result of adsorption of atomic hydrogen or during epitaxial growth. (C) 1995 American Vacuum Society.