Ga-induced atom wire formation and passivation of stepped Si(112)

TL;DR

This study combines experimental and theoretical methods to analyze Ga-induced atomic wire formation on Si(112), revealing a new passivated semiconducting surface structure with implications for 1D metallic growth.

Contribution

A new structural model of Ga on Si(112) is proposed, showing full passivation and challenging previous step-edge decoration growth ideas.

Findings

Identified Ga zig-zag chains with vacancy lines and dislocations.

Discovered the surface is fully passivated and semiconducting.

Questioned the viability of step-edge decoration for 1D metallic structures.

Abstract

We present an in-depth analysis of the atomic and electronic structure of the quasi one-dimensional (1D) surface reconstruction of Ga on Si(112) based on Scanning Tunneling Microscopy and Spectroscopy (STM and STS), Rutherford Backscattering Spectrometry (RBS) and Density Functional Theory (DFT) calculations. A new structural model of the Si(112)6 x 1-Ga surface is inferred. It consists of Ga zig-zag chains that are intersected by quasi-periodic vacancy lines or misfit dislocations. The experimentally observed meandering of the vacancy lines is caused by the co-existence of competing 6 x 1 and 5 x 1 unit cells and by the orientational disorder of symmetry breaking Si-Ga dimers inside the vacancy lines. The Ga atoms are fully coordinated, and the surface is chemically passivated. STS data reveal a semiconducting surface and show excellent agreement with calculated Local Density of States (LDOS) and STS curves. The energy gain obtained by fully passivating the surface calls the idea of step-edge decoration as a viable growth method toward 1D metallic structures into question.