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

We present the results of a calculation of zero-temperature elastic conduct ance through a finite "atomic wire" between Au pads, all supported by a Si( 001)-(2 x 1)-H surface. The atomic wire consists of a line of dangling bond s which can be fabricated by removing hydrogen atoms by applying voltage pu lses to a scanning tunneling microscopy (STM) tip along one side of a row o f H-passivated silicon dimers. Two different line configurations, without a nd with Peierls distortion, have been considered. We find that the nondisto rted line behaves like a single ballistic transmission channel. Conversely, with Peierls distortion present, tunneling occurs through the small result ing energy gap (0.2 eV), leading to inverse decay length of the current of 0.09 Angstrom(-1). The conductance of the substrate between the pads withou t 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 A ngstrom(-1). These fully three-dimensional atomistic computations represent an application of the electron-scattering quantum-chemistry method which w as previously used to calculate the conductance of ''molecular wires'' and of STM junctions with various adsorbates. Compared to molecular wires previ ously investigated by the same method, the atomic wire studied here exhibit s the smallest inverse decay length.