Phonon confinement and substitutional disorder in Cd1-xZnxS Nanocrystals

TL;DR

This study investigates 1LO optical phonons in Cd1-xZnxS nanocrystals, revealing that substitutional disorder significantly contributes to phonon line broadening beyond confinement effects, using Raman spectroscopy analysis.

Contribution

It demonstrates that substitutional disorder has a greater impact on phonon linewidth broadening than phonon confinement in mixed Cd1-xZnxS nanocrystals.

Findings

Line broadening exceeds confinement predictions

Substitutional disorder dominates linewidth broadening

1LO modes appear at lower wavenumbers in nanocrystals

Abstract

1LO optical phonons in free-standing mixed Cd1-xZnxS nanocrystals, synthesized using chemical precipitation, are investigated using Raman spectroscopy. As expected for the nanocrystals, the 1-LO modes are found to appear at slightly lower wavenumbers than those in the bulk mixed crystals and exhibit one mode behavior. On the other hand, the line broadening is found to be much more than that can be accounted on the basis of phonon confinement. From the detailed line shape analysis it turns out that the substitutional disorder in the mixed crystals contributes much more to the line broadening than the phonon confinement. The linewidth arising from these mechanisms are also extracted from the analysis.