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Proceedings Paper

Micro-Raman spectroscopic characterization ZnO quantum dots, nanocrystals, and nanowires
Author(s): Irene Calizo; Khan A. Alim; Vladimir A. Fonoberov; Sivashankar Krishnakumar; Manu Shamsa; Alexander A. Balandin; Russell Kurtz
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Paper Abstract

Nanostructures, such as quantum dots, nanocrystals and nanowires, made of wurtzite ZnO have recently attracted attention due to their proposed applications in optoelectronic devices. Raman spectroscopy has been widely used to study the optical phonon spectrum modification in ZnO nanostructures as compared to bulk crystals. Understanding the phonon spectrum change in wurtzite nanostructures is important because the optical phonons affect the light emission and absorption. The interpretation of the phonon peaks in the Raman spectrum from ZnO nanostructures continues to be the subject of debates. Here we present a comparative study of micro-Raman spectra from ZnO quantum dots, nanocrystals and nanowires. Several possible mechanisms for the peak position shifts, i.e., optical phonon confinement, phonon localization on defects and laser-induced heating, are discussed in details. We show that the shifts of ~2 cm-1 in non-Resonant spectra are likely due to the optical phonon confinement in ZnO quantum dots with the average diameter of 4 nm. The small shifts in the non-Resonant spectra from ZnO nanowires with the diameter ~20 nm - 50 nm can be attributed to either defects or large size dispersion, which results in a substantial contribution from nanowires with smaller diameters. The large red-shifts of ~10 cm-1 in the resonant Raman spectrum from nanocrystals were proved to be due to local laser heating.

Paper Details

Date Published: 6 February 2007
PDF: 8 pages
Proc. SPIE 6481, Quantum Dots, Particles, and Nanoclusters IV, 64810N (6 February 2007); doi: 10.1117/12.713648
Show Author Affiliations
Irene Calizo, Univ. of California, Riverside (United States)
Khan A. Alim, Physical Optics Corp. (United States)
Vladimir A. Fonoberov, Univ. of California, Riverside (United States)
Sivashankar Krishnakumar, Univ. of California, Riverside (United States)
Manu Shamsa, Univ. of California, Riverside (United States)
Alexander A. Balandin, Univ. of California, Riverside (United States)
Russell Kurtz, Physical Optics Corp. (United States)

Published in SPIE Proceedings Vol. 6481:
Quantum Dots, Particles, and Nanoclusters IV
Kurt G. Eyink; Diana L. Huffaker; Frank Szmulowicz, Editor(s)

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