Conductance of a finite missing hydrogen atomic line on Si(001)-(2×1)-H

Abstract

We present the results of a calculation of zero-temperature elastic conductance through a finite ``atomic wire'' between Au pads, all supported by a Si(001)-(2\ifmmode\times\else\texttimes\fi{}1)-H surface. The atomic wire consists of a line of dangling bonds which can be fabricated by removing hydrogen atoms by applying voltage pulses to a scanning tunneling microscopy (STM) tip along one side of a row of H-passivated silicon dimers. Two different line configurations, without and with Peierls distortion, have been considered. We find that the nondistorted line behaves like a single ballistic transmission channel. Conversely, with Peierls distortion present, tunneling occurs through the small resulting energy gap $(0.2 \mathrm{eV}),$ leading to inverse decay length of the current of $0.09 {\AA{}}^{\ensuremath{-}1}.$ The conductance of the substrate between the pads without the defect line has also been calculated. In this case, tunneling occurs through a much wider energy gap and a larger inverse decay length of $0.41 {\AA{}}^{\ensuremath{-}1}.$ These fully three-dimensional atomistic computations represent an application of the electron-scattering quantum-chemistry method which was previously used to calculate the conductance of ``molecular wires'' and of STM junctions with various adsorbates. Compared to molecular wires previously investigated by the same method, the atomic wire studied here exhibits the smallest inverse decay length.