Polar optical phonons in wurtzite spheroidal quantum dots: Theory and application to ZnO and ZnO/MgZnO nanostructures

TL;DR

This paper develops an analytical theory for polar optical-phonon modes in wurtzite spheroidal quantum dots and applies it to ZnO nanostructures, enabling better interpretation of Raman spectra.

Contribution

The paper introduces a new analytical model for polar optical-phonon modes in wurtzite spheroidal quantum dots, highlighting differences from zincblende structures and aiding spectral analysis.

Findings

Different phonon modes in wurtzite vs zincblende quantum dots

Accurate prediction of Raman phonon peaks in nanostructures

Application to ZnO and MgZnO nanostructures

Abstract

Polar optical-phonon modes are derived analytically for spheroidal quantum dots with wurtzite crystal structure. The developed theory is applied to a freestanding spheroidal ZnO quantum dot and to a spheroidal ZnO quantum dot embedded into a MgZnO crystal. The wurtzite (anisotropic) quantum dots are shown to have strongly different polar optical-phonon modes in comparison with zincblende (isotropic) quantum dots. The obtained results allow one to explain and accurately predict phonon peaks in the Raman spectra of wurtzite nanocrystals, nanorods (prolate spheroids), and epitaxial quantum dots (oblate spheroids).