Raman spectroscopy of wurtzite and zinc-blende GaAs nanowires: polarization dependence, selection rules and strain effects

TL;DR

This study investigates polarization-dependent Raman scattering in single GaAs nanowires with mixed wurtzite and zinc-blende structures, revealing selection rules, strain effects, and surface roughness influences on vibrational modes.

Contribution

It provides detailed polarization-dependent Raman analysis of GaAs nanowires, elucidating selection rules, strain effects, and surface roughness impacts specific to nanowire geometry.

Findings

E1(TO) mode at 267 cm-1 is strongest with parallel polarization, consistent with selection rules.

E2H mode in wurtzite GaAs varies between 254-256 cm-1 depending on phase content.

Strain between phases causes measurable shifts in Raman modes.

Abstract

Polarization dependent Raman scattering experiments realized on single GaAs nanowires with different percentages of zinc-blende and wurtzite structure are presented. The selection rules for the special case of nanowires are found and discussed. In the case of zinc-blende, the transversal optical mode E1(TO) at 267 cm-1 exhibits the highest intensity when the incident and analyzed polarization are parallel to the nanowire axis. This is a consequence of the nanowire geometry and dielectric mismatch with the environment, and in quite good agreement with the Raman selection rules. We also find a consistent splitting of 1 cm-1 of the E1(TO). The transversal optical mode related to the wurtzite structure, E2H, is measured between 254 and 256 cm-1, depending on the wurtzite content. The azymutal dependence of E2H indicates that the mode is excited with the highest efficiency when the incident and analyzed polarization are perpendicular to the nanowire axis, in agreement with the selection rules. The presence of strain between wurtzite and zinc-blende is analyzed by the relative shift of the E1(TO) and E2H modes. Finally, the influence of the surface roughness in the intensity of the longitudinal optical mode on {110} facets is presented.