Optically confined polarized resonance Raman studies in identifying crystalline orientation of sub-diffraction limited AlGaN nanostructure

TL;DR

This study demonstrates polarized resonance Raman spectroscopy combined with optical confinement effects to identify the crystalline orientation of a single sub-diffraction AlGaN nanowire, overcoming traditional scattering limitations.

Contribution

It introduces a novel optical characterization method using resonance Raman spectroscopy and optical confinement to analyze nanostructures below the diffraction limit.

Findings

Successful identification of crystalline orientation in a 100 nm AlGaN nanowire.

Validation of the technique through comparison with high-resolution TEM analysis.

Demonstration of spectroscopic analysis at sub-diffraction scales using optical confinement effects.

Abstract

An optical characterization tool of Raman spectroscopy with extremely weak scattering cross section tool is not popular to analyze scattered signal from a single nanostructure in the sub-diffraction regime. In this regard, plasmonic assisted characterization tools are only relevant in spectroscopic studies of nanoscale object in the sub-diffraction limit. We have reported polarized resonance Raman spectroscopic (RRS) studies with strong electron-phonon coupling to understand the crystalline orientation of a single AlGaN nanowire of diameter about 100 nm. AlGaN nanowire is grown by chemical vapor deposition technique using the catalyst assisted vapor-liquid-solid process. The results are compared with the high resolution transmission electron microscopic analysis. As a matter of fact, optical confinement effect due to the dielectric contrast of nanowire with respect to that of surrounding media assisted with electron-phonon coupling of RRS are useful for the spectroscopic analysis in the sub-diffraction limit of 325 nm (lamda(2N.A.)^(-1)) using an excitation wavelength (lamda) of 325 nm and near ultraviolet 40X far field objective with a numerical aperture (N.A.) value of 0.50.