Change search
ReferencesLink to record
Permanent link

Direct link
Investigation of Vibrational Modes and Phonon Density of States in ZnO Quantum Dots
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
2012 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 12, 6893-6901 p.Article in journal (Refereed) Published
Abstract [en]

The ability to understand the phonon behavior in small metal oxide nanostructures and their surfaces is of great importance for thermal and microelectronic applications in successively smaller devices. Here the development of phonons in successively larger ZnO wurtzite quantum dots (QDs) is investigated. Raman spectroscopic measurements for particles from 3 to 11 nm reveal that the E-2 Raman active optical phonon at 436 cm(-1) is the first mode to be developed with a systematic increase with particle size. We also find a broad phonon band at 260-340 attributed to surface vibrations. The E-1-LO mode at 585 cm(-1) is the next to be developed while still being strongly suppressed in the confined particles. Other modes found in bulk ZnO are not developed for particles below 11 nm. Results from density functional theory showed an excellent agreement with the experimental molecular vibrations in the zinc acetate precursor and phonon modes in bulk ZnO. To elucidate the vibration behavior and phonon development in the ZnO QDs under nonzero temperature conditions and incorporating surface reconstruction, we performed reactive force field calculations. We show that the experimentally developed phonon modes in the QDs are the ones expected from dynamic theory. In particular, we show that the surface phonon modes in the very outermost surface (5 angstrom) can explain the observed broad phonon band and give the precise relation between the intensity of the surface and bulk phonons as the particle size increases. Calculations with temperatures between 50K and 1000K also show distinction of temperature effects in the material and that the phonon peaks are not generally shifted when the system is heated and quantum confined but instead reveal a dependence on the symmetry of the phonon mode.

Place, publisher, year, edition, pages
2012. Vol. 116, no 12, 6893-6901 p.
National Category
Physical Chemistry
URN: urn:nbn:se:kth:diva-93930DOI: 10.1021/jp300985kISI: 000302051100015ScopusID: 2-s2.0-84859294949OAI: diva2:524848
Swedish Research Council
QC 20120504Available from: 2012-05-04 Created: 2012-05-03 Last updated: 2012-05-04Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Hermansson, Kersti
By organisation
Theoretical Chemistry and Biology
In the same journal
The Journal of Physical Chemistry C
Physical Chemistry

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 17 hits
ReferencesLink to record
Permanent link

Direct link