Micro-Raman investigation of optical phonons in ZnO nanocrystals

Journal Article · Wed Jun 15 04:00:00 EDT 2005 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.1944222· OSTI ID:20711770

Alim, Khan A; Fonoberov, Vladimir A; Shamsa, Manu; Balandin, Alexander A ^[1]

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1. Nano-Device Laboratory, Department of Electrical Engineering, University of California-Riverside, Riverside, California 92521 (United States)

We have measured nonresonant and resonant Raman-scattering spectra from ZnO nanocrystals with an average diameter of 20 nm. Based on our experimental data and comparison with the recently developed theory, we show that the observed shifts of the polar optical-phonon peaks in the resonant Raman spectra are not related to the spatial phonon confinement. The very weak dispersion of the polar optical phonons in ZnO nanocrystals does not lead to any noticeable redshift of the phonon peaks for 20-nm nanocrystals. The observed phonon shifts have been attributed to the local heating effects. We have demonstrated that even the low-power ultraviolet laser excitation, required for the resonant Raman spectroscopy, can lead to the strong local heating of ZnO nanocrystals. The latter causes significant (up to 14 cm{sup -1}) redshift of the optical-phonon peaks compared to their position in bulk crystals. Nonresonant Raman excitation does not produce noticeable local heating. The obtained results can be used for identification of the phonons in the Raman spectra of ZnO nanostructures.

• OSTI ID: 20711770
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 12 Vol. 97; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CONFINEMENT
CRYSTALS
DISPERSIONS
EXCITATION
EXPERIMENTAL DATA
HEAT TREATMENTS
HEATING
LASERS
NANOSTRUCTURES
PHONONS
RAMAN EFFECT
RAMAN SPECTRA
RAMAN SPECTROSCOPY
RED SHIFT
SEMICONDUCTOR MATERIALS
ULTRAVIOLET RADIATION
ZINC OXIDES