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Anomalous optical processes in photoluminescence from ultra-small quantum dots of ZnO

Kukreja, L.M.; Misra, P.; Das, A.K.; Sartor, J.; Kalt, H.

Abstract:
Ensembles of alumina capped ZnO quantum dots (ZQDs) were grown using pulsed laser deposition. The ZQDs of mean radii comparable to and smaller than the pertinent excitonic Bohr radius ( ∼ 2.34 nm), called ultrasmall quantum dots, show size dependent optical absorption edges, which follow the strong confinement model. In this model the confinement energy and Coulombic interaction energy of the localized electron-hole pairs are significantly higher than their correlation energy and the optical transitions are perceived to be nonexcitonic in nature. In photoluminescence (PL) spectra of such ZQDs of mean radius of ∼ 2.3 nm at temperatures of 6 K and above, the primary recombinations are found to be due to the surface bound and Al donor bound electron-hole pairs. The band-edge recombination peak of the PL spectra appeared at about 70 K and above, which was found to be about 166 meV Stoke and/or thermally redshifted with respect to the experimentally observed absorption edge. Almost all of the PL spectra at different temperatures conspicuously showed the LO and 2LO phonon replicas of the primary tra ... mehr


Zugehörige Institution(en) am KIT Institut für Angewandte Physik (APH)
Publikationstyp Zeitschriftenaufsatz
Jahr 2011
Sprache Englisch
Identifikator ISSN: 0734-2101
KITopen ID: 1000027109
Erschienen in Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films
Band 29
Heft 3
Seiten 03A120/1 - 8
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