4×1to7×3transition in theIn∕GexSi1−x(111)system induced by varying the substrate lattice constant

Abstract

Taking $\mathrm{Si}(111)4\ifmmode\times\else\texttimes\fi{}1\text{\ensuremath{-}}\mathrm{In}$ as a prototype reconstruction, we have examined the possibility of modifying an adsorbate-induced reconstruction by varying the averaged lattice constant of the substrate. In the experiment, the lattice constant of Si(111) substrate has been increased by forming a thin alloying ${\mathrm{Ge}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}$ layer on Si(111). It has been found that this action results in removing the $4\ifmmode\times\else\texttimes\fi{}1$ reconstruction and developing a $7\ifmmode\times\else\texttimes\fi{}3$ reconstruction, the transformation being completed when more than 0.3 ML (monolayer) of Ge has been incorporated into the substrate. The $7\ifmmode\times\else\texttimes\fi{}3$ reconstruction has a striped-shaped structure built of double rows and plausibly contains 0.1 ML of In and $0.65\ifmmode\pm\else\textpm\fi{}0.04$ ML of Si(Ge) atoms and, like the $4\ifmmode\times\else\texttimes\fi{}1$, demonstrates metallic properties. The $7\ifmmode\times\else\texttimes\fi{}3$ reconstruction is not observed in ``pure'' $\mathrm{In}∕\mathrm{Si}(111)$ and $\mathrm{In}∕\mathrm{Ge}(111)$ systems. We believe that the artificial variation of substrate lattice constant not only provides a possibility of examining the role of surface stress in reconstructions but also opens a degree of freedom for engineering other types of reconstructions.