Low Frequency Raman Scattering from Acoustic Phonon Confined in $CdS_{1-x}Se_x$ Nanoparticles in Borosilicate Glass

TL;DR

This study investigates low frequency Raman scattering in CdSSe nanoparticles embedded in borosilicate glass, identifying new confined acoustic phonon modes and attributing them to nanoparticle shape effects.

Contribution

It reports the discovery of additional phonon modes in Raman spectra and assigns them to specific confined acoustic phonons using theoretical models.

Findings

Identification of new phonon modes in Raman spectra.

Assignment of modes to overtone and torsional vibrations.

Correlation of forbidden mode appearance with nanoparticle shape.

Abstract

Phonon modes found in low frequency Raman scattering from $CdS_{1-x}Se_x$ nanocrystals embedded in borosilicate glass arising from confined acoustic phonons are investigated. In addition to the breathing modes and quadrupolar modes, two additional modes are found in the spectra. In order to assign the new modes, confined acoustic phonon frequencies are calculated using CFM, CSM and the Lamb model. Based on the ratio of the frequencies of the new modes to those of the quadrupolar mode, the new modes are assigned to first overtone of the quadrupolar mode (l=2, n=1) and l=1, n=0 torsional mode. The appearance of the forbidden torsional mode is attributed to nonspherical appearance shape of the nanoparticle found from high-resolution TEM.