Metal-semiconductor fluctuation in the Sn adatoms in the Si(111)-Sn and Ge(111)-Sn ( sqrt 3 x sqrt 3)R30 degrees reconstructions.

Abstract

The two components of the Sn 4d core level in the Si(111)-Sn and Ge(111)-Sn (\ensuremath{\surd}3\ifmmode\times\else\texttimes\fi{}\ensuremath{\surd}3)R30\ifmmode^\circ\else\textdegree\fi{} structures are proposed to arise from semiconductor-metal fluctuations in the Sn adatom layer. Adsorption of potassium on the Si(111)-Sn (\ensuremath{\surd}3\ifmmode\times\else\texttimes\fi{}\ensuremath{\surd}3)R30\ifmmode^\circ\else\textdegree\fi{} surface suppresses the metallic component and shifts the tin into a purely semiconducting phase with a filled dangling bond state.