Softening of phonons by lattice defects and structural strain in heavy ion irradiated nanocrystalline zinc oxide films

Origin of the Raman mode in nanocrystalline zinc oxide in the vicinity of A 1 (LO) phonon mode induced by energetic heavy ions is reported. The evolution of this mode in the irradiated films is ascribed to the effect of disorder and the high density of lattice defects induced by irradiation. The pre...

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Bibliographic Details
Published inJournal of applied physics Vol. 110; no. 8; pp. 083520 - 083520-6
Main Authors Singh, Fouran, Singh, R. G., Kumar, Vinod, Khan, S. A., Pivin, J. C.
Format Journal Article
LanguageEnglish
Published American Institute of Physics 15.10.2011
Subjects
Condensed Matter
Materials Science
Physics
SENSITIVE DETECTOR TELESCOPE
RAMAN-SCATTERING
ELECTRONIC EXCITATION
SPECTROSCOPY
SILICON
ZNO THIN-FILMS
TRANSIENT THERMAL-PROCESS
OPTICAL PHONONS
NANOSTRUCTURES
QUANTUM DOTS
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Summary:Origin of the Raman mode in nanocrystalline zinc oxide in the vicinity of A 1 (LO) phonon mode induced by energetic heavy ions is reported. The evolution of this mode in the irradiated films is ascribed to the effect of disorder and the high density of lattice defects induced by irradiation. The presence of such defects is confirmed by the reduction in the intensity of E 2 (high) mode and band bending of the near band edge absorption. A softening of the evolved Raman mode with increasing in ion fluence is also observed. This softening cannot be attributed to spatial confinement of phonons, as the sizes of the crystallites are large. Therefore, it is explained in terms of the combined effects of phonon localization by lattice defects and the structural strain in the lattice induced by electronic energy loss transferred by energetic heavy ions.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3651638