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

Abstract

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