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 Si(100)2x1 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(4x2) --> 2x1 surface phase transition near 200 K, which indicates that surface scattering increases with decreasing c(4x2) order on the surface. The surface conductance of Si(111) 7x7 was measured only on a SOI substrate. The temperature coefficient is metallic and the magnitude is larger than the universal conductance quantum.