Self-Doping of Gold Chains on Silicon: A New Structural Model for Si(111)5x2-Au

TL;DR

This paper proposes a new atomic-scale structural model for the Si(111)5x2-Au surface reconstruction, explaining experimental observations through first-principles calculations and a novel doping mechanism.

Contribution

It introduces a 'double honeycomb chain' model with Si adatoms that accounts for the observed periodicity and electronic features of the Si(111)5x2-Au surface.

Findings

The model reproduces STM and photoemission features.

Optimal doping occurs with one adatom per four 5x2 cells.

The structure explains the period doubling and electronic properties.

Abstract

A new structural model for the Si(111)5x2-Au reconstruction is proposed and analyzed using first-principles calculations. The basic model consists of a "double honeycomb chain" decorated by Si adatoms. The 5x1 periodicity of the honeycomb chains is doubled by the presence of a half-occupied row of Si atoms that partially rebonds the chains. Additional adatoms supply electrons that dope the parent band structure and stabilize the period doubling; the optimal doping corresponds to one adatom per four 5x2 cells, in agreement with experiment. All the main features observed in scanning tunneling microscopy and photoemission are well reproduced.