Publication date: 13th July 2024
Zinc oxide (ZnO) is a well-studied wide band gap semiconductor due to its availability, low cost and chemical stability. The light emission and vibrations of low dimensional ZnO are however less understood. Here we report the photoluminescence emission from ZnO quantum dots and their lattice vibrations, with special emphasis of exciton and defect state emission. It is shown that the fluorescence emission partly originates from surface states and the positions of these surface states within the bandgap are calculated. In a light emitting material energy can be lost through a conversion into thermal energy. This conversion is facilitated through an interaction between the excited state wave function and the lattice vibrations in the material and is dependent on the electron-phonon coupling. The intensity ratio between the Raman peaks of the fundamental longitudinal optical (LO) mode and its overtones, in resonance Raman spectroscopy, can be used as a measure of the electron-phonon coupling strength and we have used this to investigate how the electron-phonon coupling depends on particle size in nano dimensional ZnO.
This work was supported by the Swedish research council for sustainable development (Svenska forskningsrådet FORMAS, FORMAS-2016-00908) and the Swedish Research Council (Vetenskapsrådet, project id 2019-05591 and 2023-05244).
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