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)-(2×1)-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 $\left(0.2\mathrm{}\hspace{0.5em}\mathrm{eV}\right),$ leading to inverse decay length of the current of $0.09\hspace{0.5em}{\AA }^{-1}.$ 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 $0.41\hspace{0.5em}{\AA }^{-1}.$ 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.