Systematic investigation of the structure of the Si(553)-Au surface from first principles

Abstract

We present here a comprehensive search for the structure of the Si͑553͒-Au reconstruction. More than 200 different trial structures have been studied using first-principles density-functional calculations with the SIESTA code. An iterative procedure, with a step-by-step increase in the accuracy and computational cost of the calculations, was used to allow for the study of this large number of configurations. We have considered reconstructions restricted to the topmost bilayer and studied two types: ͑i͒ "flat" surface-bilayer models, where atoms at the topmost bilayer present different coordinations and registries with the underlying bulk, and ͑ii͒ nine different models based on the substitution of a silicon atom by a gold atom in different positions of a -bonded chain reconstruction of the Si͑553͒ surface. We have developed a compact notation that allows us to label and identify all these structures. This is very useful for the automatic generation of trial geometries and for counting the number of inequivalent structures, i.e., structures that have different bonding topologies. The most stable models are those that exhibit a honeycomb-chain structure at the step edge. One of our models ͑model "f2"͒ reproduces the main features of the room temperature photoemission and scanning-tunneling microscopy data. Thus, we conclude that this model is a good candidate for the high temperature structure of the Si͑553͒-Au surface.

Structural Study of the Si(553)-Au Surface

“…The present model is very similar to the f3 model by Riikonen et al [11]. In their first-principles calculations, they found that this model is one of the most stable models, but the calculated band structure is different from the experimental band structure.…”

“…The Si atoms near the step edge are reconstructing to make a honey-comb chain. These features are similar to the accepted model for the Si(557)-Au surface [13] and also to most previously proposed models for the Si(553)-Au surface [10,11]. The Patterson map calculated from this model (Fig.…”

“…The band structure of none of these models, however, is fully consistent with the experimental one [11]. Further experimental input is therefore needed to determine the correct structure model.…”

“…2(a). [11]. The circle marks the position of a peak in the experimental Patterson map that does not appear in Fig.…”

“…In addition, this model was found to be unstable in density functional theory calculations [9]. A number of other models have been proposed from first-principles calculations and scanning tunneling microscopy images [3,10,11]. These models generally have a single gold atom substituting for Si * This paper was presented at International Symposium on Surface Science and Nanotechnology (ISSS-5), Waseda University, Japan, 9-13 November, 2008.…”