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Single dot optical spectroscopy of silicon nanocrystals: Low temperature measurements
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.ORCID iD: 0000-0003-2562-0540
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
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2005 (English)In: Optical materials (Amsterdam), ISSN 0925-3467, Vol. 27, no 5, 973-976 p.Article in journal (Refereed) Published
Abstract [en]

Single dot spectroscopy allows studying properties of a single nanocrystal avoiding inhomogeneous broadening of the emission band. Here, data obtained by this technique for Si nanocrystals fabricated by electron beam lithography, plasma etching and subsequent size-reduction by oxidation are presented. First, blinking (on–off intermittence) of the luminescence was observed for most individual nanocrystals, although some exhibited relatively stable luminescence. As a result of the quantum confinement effect spectra with different emission wavelengths for different nanocrystals were recorded. While at room temperature the full width at half-maximum of the nanocrystal emission peaks was measured to be 100–150 meV, at 80 K the linewidth for some dots appeared to be about 25 meV only. The observed temperature dependence of the homogeneous linewidth may lead to an understanding of the exciton–phonon interaction in indirect band-gap quantum dots.

Place, publisher, year, edition, pages
2005. Vol. 27, no 5, 973-976 p.
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-6700DOI: 10.1016/j.optmat.2004.08.046ISI: 000227621300048Scopus ID: 2-s2.0-13444273345OAI: oai:DiVA.org:kth-6700DiVA: diva2:11481
Note
QC 20100922 QC 20111011. Symposium of the European-Materials-Research-Society on Si-Based Photonics - Towards True Monolithic Integration. Strasbourg, FRANCE. MAY 25-28, 2004. Tidigare titel: Single dot optical spectroscopy of silicon nanocrystals: Low-T measurements Available from: 2006-12-29 Created: 2006-12-29 Last updated: 2011-10-11Bibliographically 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
Opponent
Supervisors
Note
QC 20100922Available from: 2006-12-29 Created: 2006-12-29 Last updated: 2011-10-11Bibliographically approved

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Publisher's full textScopushttp://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXP-4DHX928-9&_user=4478132&_coverDate=02%2F28%2F2005&_alid=515494394&_rdoc=1&_fmt=summary&_orig=search&_cdi=5596&_sort=d&_docanchor=&view=c&_acct=C000034958&_version=1&_urlVersion=0&_userid=4478132&md5=a96f9d9c996a31f555890f27f13dc04d

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Sychugov, IlyaLinnros, Jan

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