Edge-driven transition in surface structure of nanoscale silicon

TL;DR

This study uses ab initio methods to explore how surface and edge effects influence the structure of nanoscale silicon, revealing a size-dependent phase transition affecting electronic but not elastic properties.

Contribution

It identifies a size-dependent edge-driven phase transition in nanoscale silicon structures, highlighting the importance of edge effects at the 3 nm scale.

Findings

Two competing low-energy reconstructions in nanoscale silicon bars.

A phase transition as the cross section decreases.

Electronic structure signatures of the transition, with minimal impact on elasticity.

Abstract

We present an ab initio exploration of the phenomena which will become important for freestanding structures of silicon as they are realized on the nanoscale. We find that not only surface but also edge effects are important considerations in structures of dimensions on the order of 3 nm. Specifically, for long nanoscale silicon bars, we find two competing low-energy reconstructions with a transition from one to the other as the cross section of the bar decreases. We predict that this size-dependent phase transition has a signature in the electronic structure of the bar but little effect on elastic properties.