Size dependence of the bulk and surface phonon modes of gallium arsenide nanowires as measured by Raman Spectroscopy

TL;DR

This study investigates how the size of gallium arsenide nanowires influences their bulk and surface phonon modes using Raman spectroscopy, revealing size-dependent shifts consistent with theoretical predictions.

Contribution

It provides experimental evidence of size-dependent surface phonon mode shifts in GaAs nanowires, aligning with theoretical models and expanding understanding of phonon behavior at nanoscale.

Findings

Surface phonon mode shifts to lower frequencies with decreasing nanowire diameter.

Optical phonon modes exhibit small line widths indicating high crystalline quality.

Surface mode behavior agrees with theoretical predictions based on dielectric environment.

Abstract

Gallium arsenide nanowires were synthesized by gallium-assisted molecular beam epitaxy. By varying the growth time, nanowires with diameters ranging from 30 to 160 nm were obtained. Raman spectra of the nanowires ensembles were measured. The small line width of the optical phonon modes agree with an excellent crystalline quality. A surface phonon mode was also revealed, as a shoulder at lower frequencies of the longitudinal optical mode. In agreement with the theory, the surface mode shifts to lower wave numbers when the diameter of the nanowires is decreased or the environment dielectric constant increased.