Electrical conductance of reconstructed silicon surfaces

The electrical conductance of atomically clean, reconstructed silicon surfaces was studied as a function of temperature with macroscopic van der Pauw measurements in ultrahigh vacuum. The surface-state conductance of the $\mathrm{Si}(100)2\ifmmode\times\else\texttimes\fi{}1$ surface was measured on a fully depleted silicon-on-insulator (SOI) substrate and on bulk Si. The surface-state conductance has metallic temperature dependence, but its magnitude falls below the universal conductance quantum. The data furthermore reveal a clear signature of the $c(4\ifmmode\times\else\texttimes\fi{}2)\ensuremath{\rightarrow}2\ifmmode\times\else\texttimes\fi{}1$ surface phase transition near 200 K, which indicates that surface scattering increases with decreasing $c(4\ifmmode\times\else\texttimes\fi{}2)$ order on the surface. The surface conductance of $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ was measured only on a SOI substrate. The temperature coefficient is metallic and the magnitude is larger than the universal conductance quantum.