Interfacial and Confined Optical Phonons in Wurtzite Nanocrystals

TL;DR

This paper develops a dielectric-continuum model to analyze interface and confined optical phonons in wurtzite nanocrystals, revealing unique discrete spectra and matching experimental Raman data for ZnO quantum dots.

Contribution

It introduces a new theoretical framework for confined phonons in wurtzite nanocrystals, highlighting differences from zincblende structures and validating with experimental results.

Findings

Confined polar optical phonons in wurtzite nanocrystals have a discrete frequency spectrum.

The model's predictions agree well with experimental Raman spectra of ZnO quantum dots.

Confined phonon frequencies differ from bulk crystal phonons in wurtzite structures.

Abstract

We derive within the dielectric-continuum model an integral equation that defines interface and confined polar optical-phonon modes in nanocrystals with wurtzite crystal structure. It is demonstrated theoretically, that while the frequency of confined polar optical phonons in zincblende nanocrystals is equal to that of the bulk crystal phonons, the confined polar optical phonons in wurtzite nanocrystals have a discrete spectrum of frequencies different from those of the bulk crystal. The calculated frequencies of confined polar optical phonons in wurtzite ZnO nanocrystals are found to be in an excellent agreement with the experimental resonant Raman scattering spectra of spherical ZnO quantum dots.