First-principles Structural and Electronic Characterization of Ordered SiO2 Nanowires

TL;DR

This study uses first-principles calculations to analyze the structure and electronic properties of SiO2 nanowires, revealing their semiconducting nature and potential for band gap engineering based on structural variations.

Contribution

It provides a detailed first-principles characterization of SiO2 nanowires derived from various crystal structures, including electronic and bonding properties, validated by advanced many-body calculations.

Findings

Many SiO2 nanowires are semiconductors, unlike their bulk counterparts.

Surface states can influence the electronic gap in thick rutile-like nanowires.

Band gaps can be tuned by altering nanowire structure and thickness.

Abstract

Density functional theory and molecular dynamics simulations have been used to optimize the structure of nanowires of SiO2. The starting structures were based on b-cristobalite, orthotridymite, b-tridymite, and rutile crystals. The analysis of the electronic structure has been validated by many-body perturbation calculations using the G0W0 and GW + Bethe-Salpeter equation approximations, in order to account for quasi-particle and excitonic effects. The calculations indicate that many of these nanowires have semiconducting character, while the corresponding bulk solids are insulators. In the case of thick rutile-like nanowires we found the gap congested with surface states. Electronic charge is transferred from silicon atoms to oxygen atoms, and the bonding in the nanowires is partly ionic and partly covalent. The magnitude of the band gap can be engineered by changing the structure and the thickness of the nanowires.