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Electron tomography analysis of 3D order and interfacial structure in nano-precipitates
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Electron Microscopy and Nanoengineering group)
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 [en]
Electron tomography, nanoprecipitate, interfacial structure.
National Category
Physical Sciences
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-284102ISBN: 978-91-554-9590-9 (print)OAI: oai:DiVA.org:uu-284102DiVA: diva2:921664
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
List of papers
1. Indium tin oxide-silicon nanocrystal nanocomposite grown by aerosol assisted chemical vapour deposition
Open this publication in new window or tab >>Indium tin oxide-silicon nanocrystal nanocomposite grown by aerosol assisted chemical vapour deposition
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2015 (English)In: Journal of Sol-Gel Science and Technology, ISSN 0928-0707, E-ISSN 1573-4846, Vol. 73, no 3, 666-672 p.Article in journal (Refereed) Published
Abstract [en]

Nanocomposite films were successfully grown by aerosol-assisted chemical vapour deposition (CVD) in a single deposition step using a mixture of indium tin neodecanoate and ligand stabilised silicon nanocrystals. Samples were analysed by HRTEM and silicon nanocrystals with a density of 1.2 x 10(12) cm(-2) were observed. From the reconstructed 3D tomogram, the averaged distance between the nearest nanoparticles is 8.3 nm and the 3D density of nanoparticles is 1.6 x 10(18) cm(-3). An animation of the 3D reconstruction is supplied in the supporting information. These data show the versatility of aerosol assisted CVD in achieving a nanocomposite with such a density of silicon nanocrystals, of carefully controlled size and shape, within a polycrystalline host matrix. Therefore, meeting the density and size distribution requirements of particle inclusion in active nanocomposites for photovoltaic structures. ITO-silicon nanocrystal nanocomposite samples were analysed by HRTEM and silicon nanocrystals with a density of 1.2 x 10(12) cm(-2) were observed. From the reconstructed 3D tomogram, the averaged distance between the nearest nanoparticles is 8.3 nm and the 3D density of nanoparticles is 1.6 x 10(18) cm(-3). [GRAPHICS] .

Keyword
Nanocrystal, Nanocomposite, Aerosol-assisted CVD, HR-TEM tomography
National Category
Other Engineering and Technologies
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-251504 (URN)10.1007/s10971-015-3618-3 (DOI)000350684600023 ()
Conference
European Materials Research Society (EMRS) Spring Meeting / Symposium I on Solution Processing and Properties of Functional Oxide Thin Films and Nanostructures, MAY 26-30, 2014, Lille, FRANCE
Available from: 2015-04-22 Created: 2015-04-20 Last updated: 2017-12-04Bibliographically approved
2. Nanocrystal size distribution analysis from transmission electron microscopy images
Open this publication in new window or tab >>Nanocrystal size distribution analysis from transmission electron microscopy images
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2015 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 48, 20593-20606 p.Article in journal (Refereed) Published
Abstract [en]

We propose a method, with minimal bias caused by user input, to quickly detect and measure the nanocrystal size distribution from transmission electron microscopy (TEM) images using a combination of Laplacian of Gaussian filters and non-maximum suppression. We demonstrate the proposed method on bright-field TEM images of an a-SiC:H sample containing embedded silicon nanocrystals with varying magnifications and we compare the accuracy and speed with size distributions obtained by manual measurements, a thresholding method and PEBBLES. Finally, we analytically consider the error induced by slicing nanocrystals during TEM sample preparation on the measured nanocrystal size distribution and formulate an equation to correct this effect.

National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:uu:diva-272431 (URN)10.1039/c5nr06292f (DOI)000365982700031 ()26593390 (PubMedID)
Available from: 2016-01-14 Created: 2016-01-13 Last updated: 2017-11-30Bibliographically approved
3. Optoelectronic properties of p-i-n heterojunctions based on germanium nanocrystals
Open this publication in new window or tab >>Optoelectronic properties of p-i-n heterojunctions based on germanium nanocrystals
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2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, no 3, 033510- p.Article in journal (Refereed) Published
Abstract [en]

We investigated the possibility of using physical vapour deposited Ge nanocrystals (NCs) in optoelectronic devices such as solar cells. We have prepared p-i-n heterojunctions based on p(+)-doped Si substrate/undoped Ge NCs/ZnO: Al layer stacks and their optoelectronic properties were characterised. Under light, the generation of photo-carriers from the Ge NCs themselves was demonstrated. The photovoltaic behaviour of the p-i-n structure was also highlighted, with a measured Voc of 224 mV compared to 580 mV in theory. The discrepancy between theory and experiment was discussed on the basis of TEM observations, optical and carrier generation measurements as well as modelling.

National Category
Natural Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-208385 (URN)10.1063/1.4813616 (DOI)000322202700025 ()
Available from: 2013-09-30 Created: 2013-09-30 Last updated: 2017-12-06Bibliographically approved
4. Silicon nanocrystals on amorphous silicon carbide alloy thin films: Control of film properties and nanocrystals growth
Open this publication in new window or tab >>Silicon nanocrystals on amorphous silicon carbide alloy thin films: Control of film properties and nanocrystals growth
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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
Keyword
Silicon nanocrystal, silicon carbide, thin film
National Category
Other Materials Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-184843 (URN)10.1016/j.tsf.2012.08.046 (DOI)000310782000028 ()
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
5. Silicon nanocrystals: Novel synthesis routes for photovoltaic applications
Open this publication in new window or tab >>Silicon nanocrystals: Novel synthesis routes for photovoltaic applications
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2013 (English)In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 210, no 4, 649-657 p.Article in journal (Refereed) Published
Abstract [en]

Novel processes were developed for fabricating silicon nanocrystals and nanocomposite materials which could be used as absorbers in third generation photovoltaic devices. A conventional high-temperature annealing technique was studied as a reference process, with some new insights in crystallisation mechanisms. Innovative methods for silicon nanocrystal synthesis at much lower temperature were demonstrated, namely chemical vapour deposition (CVD), physical vapour deposition (PVD) and aerosol-assisted CVD. Besides the advantage of low substrate temperature, these new techniques allow to fabricate silicon nanocrystals embedded in wide bandgap semiconductor host matrices, with a high density and a narrow size dispersion.

Keyword
nanocrystals, nanoparticles, photovoltaics, silicon
National Category
Composite Science and Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-184849 (URN)10.1002/pssa.201200533 (DOI)000317290300004 ()
Funder
EU, FP7, Seventh Framework Programme
Available from: 2012-11-16 Created: 2012-11-15 Last updated: 2017-12-07Bibliographically approved
6. Bonding symmetry and structural analysis of the hIAPP protein aggregates using the electron tomography technique
Open this publication in new window or tab >>Bonding symmetry and structural analysis of the hIAPP protein aggregates using the electron tomography technique
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(English)Manuscript (preprint) (Other academic)
Keyword
Electron tomography, amyloid peptide
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-284098 (URN)
Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2016-06-15
7. Electron tomography analysis of the interfacial nanostructures between the Si networks and SiC nanoparticles in the thermally annealed Si rich SiC films
Open this publication in new window or tab >>Electron tomography analysis of the interfacial nanostructures between the Si networks and SiC nanoparticles in the thermally annealed Si rich SiC films
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(English)Manuscript (preprint) (Other academic)
Keyword
Electron tomography, third generation solar cell, nanoparticle, Si rich SiC film
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-284101 (URN)
Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2016-06-15

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