Identification of the Au coverage and structure of the Au/Si(111)-5x2 surface

TL;DR

This study uses density functional theory to determine the atomic structure and electronic properties of the Au/Si(111)-5x2 surface, revealing a stable model that explains its metallic nature and Si adatom behavior.

Contribution

The paper presents a new atomic model for the Au/Si(111)-5x2 surface that is energetically favored and accurately reproduces experimental STM images.

Findings

Identified a stable 5x2 atomic structure with seven Au atoms per unit cell.

Reproduced Y- and V-shaped STM images consistent with experimental data.

Showed the surface is metallic with a half-filled surface state band.

Abstract

We identify the atomic structure of the Au/Si(111)-5x2 surface by using density functional theory calculations. With seven Au atoms per unit cell, our model forms a bona fide 5x2 atomic structure, which is energetically favored over the leading model of Erwin, Barke, and Himpsel [Phys. Rev. B 80, 155409 (2009)] and well reproduces the Y- and V-shaped 5x2 STM images. This surface is metallic with a prominent half-filled band of surface states, mostly localized around the Au-chain area. The correct identification of the atomic and band structure of the clean surface further clarifies the adsorption structure of Si adatoms and the physical origin of the intriguing metal-to-insulator transition driven by Si adatoms.