Reconstructions of GaAs(1¯ 1¯ 1¯) surfaces observed by scanning tunneling microscopy

Abstract

We present scanning tunneling microscopy images of the As-rich (2\ifmmode\times\else\texttimes\fi{}2) and the Ga-rich (\ensuremath{\surd}19 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}19 ) reconstructions of the GaAs(1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{}) surface produced in situ by molecular-beam epitaxy. From the experimental results and total-energy calculations we show that the (2\ifmmode\times\else\texttimes\fi{}2) surface consists of As adatom trimers bonded to the underlying surface. The (\ensuremath{\surd}19 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}19 ) unit cell is dominated by a two-layer hexagonal ring.