Abstract
The quasi-one-dimensional Si(557)-Au reconstruction has attracted a lot of attention in recent years. We study here the interplay between the electronic and structural degrees of freedom in this system. Our calculations are in good agreement with recent experimental data obtained using scanning tunneling microscopy and spectroscopy both at room and low temperatures. Together with the quite successful description of the experimental band structure, these results give further support to the current structural model of the Si(557)-Au surface. We consider in detail the energetics and variation of the band structure as a function of the buckling of the step edge and its implications to explain the observed metal-insulator transition. Finally, we present the results of a first-principles molecular dynamics simulation of several picoseconds performed at room temperature. As expected, we find a strong oscillation of the step-edge atoms. The dynamics associated with other vibrational modes is also observed. Particularly apparent are the oscillations of the height of the restatoms and adatoms and the associated fluctuation of the Si--Au--Si bond angles along the gold chain. This mode, together with step-edge buckling, has a strong influence on the insulating and/or metallic character of the surface.
Highlights
An interesting family of quasi-one-dimensional reconstructions is formed by the deposition of submonolayer amounts of gold on flat and vicinal Si111͒ surfaces.1,2 These structures are characterized by the formation of ordered arrays of gold wires with cross sections of atomic dimensions
Apparent are the oscillations of the height of the restatoms and adatoms and the associated fluctuation of the Si–Au–Si bond angles along the gold chain
The gold chains are spatially well separated from the step edgesee the structure in Fig. 1͒ and, the Si-Au bands should not be affected by a Peierls-type distortion of the step edge
Summary
An interesting family of quasi-one-dimensional reconstructions is formed by the deposition of submonolayer amounts of gold on flat and vicinal Si111͒ surfaces. These structures are characterized by the formation of ordered arrays of gold wires with cross sections of atomic dimensions. An interesting family of quasi-one-dimensional reconstructions is formed by the deposition of submonolayer amounts of gold on flat and vicinal Si111͒ surfaces.1,2 These structures are characterized by the formation of ordered arrays of gold wires with cross sections of atomic dimensions. An alternative explanation was given by us in Ref. 11 and supported by calculations showing a nice agreement with the experimentally measured band structure: the two proximal bands would appear due to the spin-orbitSOsplittingRashba effectof a one-dimensional band associated with the gold chains. This model has received some experimental support recently. One of the two proximal one-dimensional bands was shown to suffer a metal-insulator transition, while the other band was claimed not to cross EFi.e., remain insulatingindependently of the temperature.
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