Electrical transport in a two-dimensional electron and hole gas on a Si(001)-(2x1) surface

Si(001)-(2x1) surface is one of the many two-dimensional systems of scientific and applied interest. Due to its asymmetric dimer reconstruction, transport through this surface can be considered in two distinct directions, i.e., along and perpendicular to the paired dimer rows. We calculate the zero-bias conductance of these surface states under flatband condition and find that conduction along the dimer row direction is significant due to strong orbital hybridization. Additionally, we find that the surface conductance is orders of magnitude higher than the bulk conductance close to the band edges for the unpassivated surface at room temperature. Thus, we propose that the transport through these surface states may be the dominant conduction mechanisms in the recently reported scanning tunneling microscopy of silicon nanomembranes. The zero-bias conductance is also calculated for the weakly interacting dangling-bond wires along and perpendicular to the dimer row direction and similar trends are obtained. The extended Huckel theory is used for the electronic structure calculations.