Metallic Indium Monolayers on Si(111)

TL;DR

This study uses density-functional calculations to predict and analyze two metastable monolayer indium phases on Si(111), revealing quasi-1D metallic structures that suggest the realization of the 2D limit of free-electron-like indium overlayers.

Contribution

The paper predicts two new metastable monolayer indium phases on Si(111) with specific structures and properties, advancing understanding of 2D metallic materials.

Findings

Two metastable In monolayer phases match experimental data.

Both phases exhibit quasi-1D arrangements and anisotropic metallic band structures.

The results suggest the 2D free-electron-like limit of In overlayers has been achieved.

Abstract

Density-functional calculations are used to identify one-atom-thick metallic In overlayers on the Si(111) surface, which have long been sought in quest of the ultimate two-dimensional (2D) limit of free-electron-like metallic properties. We predict two metastable single-layer In phases, one $\sqrt{7}\times\sqrt{3}$ phase with a coverage of 1.4 monolayer (ML; here 1 ML refers to one In atom per top Si atom) and the other $\sqrt{7}\times\sqrt{7}$ phase with 1.43 ML, which indeed match well with experimental evidences. Both phases reveal quasi-1D arrangements of protruded In atoms, leading to 2D-metallic but anisotropic band structures and Fermi surfaces. This directional feature contrasts with the free-electron-like In-overlayer properties that are known to persist up to the double-layer thickness, implying that we may have achieved the 2D limit of free-electron-like In overlayers in previous studies of double-layer In phases.