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Silicon nanocrystals on amorphous silicon carbide alloy thin films: Control of film properties and nanocrystals growth
CEA, Liten, Grenoble, och Université de Toulouse, UPS, INPT, LAPLACE, Frankrike.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
CEA, Liten, Grenoble, Frankrike.
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2012 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 522, 136-144 p.Article in journal (Refereed) Published
Abstract [en]

The present study demonstrates the growth of silicon nanocrystals on amorphous silicon carbide alloy thin films. Amorphous silicon carbide films [a-Si1 − xCx:H (with x < 0.3)] were obtained by plasma enhanced chemical vapor deposition from a mixture of silane and methane diluted in hydrogen. The effect of varying the precursor gas-flow ratio on the film properties was investigated. In particular, a wide optical band gap (2.3 eV) was reached by using a high methane-to-silane flow ratio during the deposition of the a-Si1 − xCx:H layer. The effect of short-time annealing at 700 °C on the composition and properties of the layer was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was observed that the silicon-to-carbon ratio in the layer remains unchanged after short-time annealing, but the reorganization of the film due to a large dehydrogenation leads to a higher density of SiC bonds. Moreover, the film remains amorphous after the performed short-time annealing. In a second part, it was shown that a high density (1 × 1012 cm− 2) of silicon nanocrystals can be grown by low pressure chemical vapor deposition on a-Si0.8C0.2 surfaces at 700 °C, from silane diluted in hydrogen. The influence of growth time and silane partial pressure on nanocrystals size and density was studied. It was also found that amorphous silicon carbide surfaces enhance silicon nanocrystal nucleation with respect to SiO2, due to the differences in surface chemical properties.

Place, publisher, year, edition, pages
Elsevier, 2012. Vol. 522, 136-144 p.
Keyword [en]
Silicon nanocrystal, silicon carbide, thin film
National Category
Other Materials Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-184843DOI: 10.1016/j.tsf.2012.08.046ISI: 000310782000028OAI: oai:DiVA.org:uu-184843DiVA: diva2:568017
Conference
EMRS 2011 symp Q
Funder
EU, FP7, Seventh Framework Programme
Available from: 2012-11-16 Created: 2012-11-15 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Electron tomography analysis of 3D order and interfacial structure in nano-precipitates
Open this publication in new window or tab >>Electron tomography analysis of 3D order and interfacial structure in nano-precipitates
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Structural characterization is essential to understand the formation mechanisms of the nanostructures in thin absorber layers in third generation solar cells and amyloid protein aggregates. Since to the dimension of the precipitated structures is in nanometer scale, electron tomography technique in transmission electron microscopy (TEM) has been applied as a major tool to analyze the 3D order and distribution of precipitates using the electron tomography technique. 

Silicon rich silicon carbide (SRSC) films were deposited by plasma enhanced chemical vapor deposition (PECVD) technique and annealed in the nitrogen atmosphere for 1 hour at 1100 °C. The spectrum-imaging (SI) technique in Energy filtered TEM (EFTEM) imaging mode was used to develop electron tomography. From the reconstructed sub-volumes, the complex, three dimensional interfacial nanostructure between the precipitated NPs and their parental matrix was observed and explained in terms of thermodynamic concepts. Additionally, the feasibility of raw data 4D electron tomography has been demonstrated using the EFTEM SI dataset.

The aggregation process of the human islet amyloid polypeptide (hIAPP) has a great impact on human health. In this thesis, a model system has been taken to study the ultrastructure of the hIAPP aggregates that are present in the fat body tissue surrounding the brain of Drosophila melanogaster. Electron tomography technique on TEM revealed clear crystalline structures in 3D. For the first time, the presence of a 5-fold twinned structure in biology was discovered. An intriguing finding is the filament like interconnection of hIAPP protein granules observed predominantly along the nearest neighbor directions. This suggests the existence of the directional binding forces between two nearest protein granules in addition to dipole-dipole interactions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 84 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1380
Keyword
Electron tomography, nanoprecipitate, interfacial structure.
National Category
Physical Sciences
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-284102 (URN)978-91-554-9590-9 (ISBN)
Public defence
2016-06-14, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2016-05-23 Created: 2016-04-15 Last updated: 2016-06-15

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Xie, LingLeifer, Klaus

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