Silicon nanowire band gap modification

TL;DR

This study uses density functional theory to analyze how different surface terminations affect the band gap of small silicon nanowires, revealing that surface chemistry can significantly modify electronic properties.

Contribution

It demonstrates that surface functional groups can cause substantial band gap shifts in silicon nanowires, highlighting the interplay between surface chemistry and quantum confinement effects.

Findings

Band gap increases as wire diameter decreases due to quantum confinement.

Surface termination can shift band gaps by up to an electronvolt.

Hybridization between silicon valence band and surface groups influences band gap modifications.

Abstract

Band gap modification for small-diameter (1 nm) silicon nanowires resulting from the use of different species for surface termination is investigated by density functional theory calculations. Because of quantum confinement, small-diameter wires exhibit a direct band gap that increases as the wire diameter narrows, irrespective of surface termination. This effect has been observed in previous experimental and theoretical studies for hydrogenated wires. For a fixed cross-section, the functional group used to saturate the silicon surface significantly modifies the band gap, resulting in relative energy shifts of up to an electronvolt. The band gap shifts are traced to details of the hybridization between the silicon valence band and the frontier orbitals of the terminating group, which is in competition with quantum confinement.