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Light emission from silicon nanocrystals: probing a single quantum do
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.ORCID iD: 0000-0003-2562-0540
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
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2006 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, 5249-5253 p.Article in journal (Refereed) Published
Abstract [en]

Analysis of low-temperature photoluminescence measurements performed on single silicon nanocrystals is presented. The luminescence emission linewidth of Si nanocrystals is found to be less than thermal broadening at low temperature, confirming the atomic-like nature of their energetic states. Beside the main peak the low-temperature spectra reveal a similar to 6 meV replica, the origin of which is discussed. For some of the investigated dots, we also observe a similar to 60 meV transverse optical (TO) phonon replica. The regular arrangement of individual nanocrystals used in this work enables combined high-resolution transmission electron microscopy (TEM) and low-temperature photoluminescence characterization of the same single quantum dot.

Place, publisher, year, edition, pages
Elsevier, 2006. Vol. 252, no 15, 5249-5253 p.
Keyword [en]
silicon nanocrystal, luminescence, electron-phonon interactions, semiconductor nanocrystals
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-6701DOI: 10.1016/j.apsusc.2005.12.030ISI: 000238623300003Scopus ID: 2-s2.0-33744533732OAI: oai:DiVA.org:kth-6701DiVA: diva2:11482
Conference
8th International Conference on Atomically Controlled Surfaces, Interfaces, and Nanostructures/13th International Congress on Thin Films Stockholm, SWEDEN, JUN 20-23, 2005
Note
QC 20100922. Conference: 8th International Conference on Atomically Controlled Surfaces, Interfaces, and Nanostructures/13th International Congress on Thin Films. Stockholm, SWEDEN. JUN 20-23, 2005 Available from: 2012-01-27 Created: 2006-12-29 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Synthesis and properties of single luminescent silicon quantum dots
Open this publication in new window or tab >>Synthesis and properties of single luminescent silicon quantum dots
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Silicon is an ubiquitous electronic material and the discovery of strong room temperature luminescence from porous Si in 1990 raised hopes it may find a new lease of life in the emerging field of optoelectronics. First, the luminescence was shown to be emitted from nanostructures remained in a porous Si network. Later the same emission was shown from Si nanocrystals and the concept of a Si quantum dot emerged. Yet a number of different models have been proposed for the origin of light emission. Some involved interface states between a Si nanocrystal and the surrounding shell, while others considered the effect of quantum confinement in an indirect bandgap semiconductor.

In this work a single Si nanocrystal was addressed to shed light on the mechanism of luminescence. Nanocrystals were prepared using e-beam lithography with subsequent etching and oxidation of silicon nanopillars. In particular, the non-uniform oxidation in self-limiting regime was successfully used to form a single nanocrystal inside nanopillars. This preparation method allowed optical probing of a single nanocrystal with far-field optics.

Results revealed sharp luminescence spectra at low temperatures with a linewidth less than the corresponding thermal broadening. This property is a signature of energy level discreetness, which is, in turn, a straightforward consequence of the quantum confinement model. Another effect observed was a random on-off blinking, which is also regarded as a hallmark of single fluorescent objects. This effect appeared to be dependent on the excitation power density suggesting the involvement of Auger-assisted ionization in the dynamics of nanocrystal luminescence. In addition, it was shown how a change in the optical mode density affects the main parameters of luminescence from Si nanocrystals, such as the radiative lifetime, the quantum efficiency and the total yield.

Finally, in order to clarify the influence of morphological properties, such as size or shape, of a Si quantum dot on its luminescence, combined low-temperature photoluminescence and transmission electron microscopy investigations were initiated. A method was developed using focused ion beam preparation for such a joint characterization.

To conclude, the work gives support to the quantum confinement effect in explaining the light emission mechanism from nano-sized Si, as well as highlights the importance of morphological structure in the luminescence process.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 55 p.
Series
Trita-ICT/MAP, 2007:1
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-4254 (URN)91-7178-533-7 (ISBN)
Public defence
2007-01-19, Aula N2, Electrum-3, Isafjordsgatan 28, Kista, 10:15
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Supervisors
Note
QC 20100922Available from: 2006-12-29 Created: 2006-12-29 Last updated: 2011-10-11Bibliographically approved

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