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Atomic layer deposition of titanium dioxide nanostructures using carbon nanosheets as a template
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
Department of Applied Science,College of William and Mary.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
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2009 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 311, no 2, 373-377 p.Article in journal (Refereed) Published
Abstract [en]

Nanostructured films of anatase TiO2 is deposited on carbon nanosheet (CNS) templates using atomic layer deposition (ALD). The high-surface area of the CNS together with the unique step coverage of the ALD process makes it possible to obtain sheet-like TiO2 nanostructures, for use in potential applications, e.g. photocatalysis and photovoltaics. A problem with ALD on CNS was the low nucleation rate giving TiO2 films with pinholes. It is shown that introduction of defects by an acid-treatment process can be used to control initial nucleation and growth of the films. The TiO2 on the defect-rich CNS nucleates faster and results in a film with no observable pinholes consisting of crystalline grains in an amorphous matrix.

Place, publisher, year, edition, pages
2009. Vol. 311, no 2, 373-377 p.
Keyword [en]
ALD, Nucleation, Atomic layer epitaxy, Nanomaterials, Oxides
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97311DOI: 10.1016/j.jcrysgro.2008.10.035ISI: 000263700300030OAI: oai:DiVA.org:uu-97311DiVA: diva2:172187
Available from: 2008-05-14 Created: 2008-05-14 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Fabrication and Functionalization of Graphene and Other Carbon Nanomaterials in Solution
Open this publication in new window or tab >>Fabrication and Functionalization of Graphene and Other Carbon Nanomaterials in Solution
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the last decades several new nanostructures of carbon have been discovered, including carbon nanotubes (CNTs), and the recently discovered 2-dimensional graphene. These new materials exhibit extraordinary and unique properties—making them extremely interesting both for fundamental science and for future applications. It is, however, of crucial importance to develop new and improved fabrication and processing methods for these carbon nanomaterials. In this thesis the concept of applying solution chemistry and solution-based techniques to fabricate and to deposit graphene and other carbon nanomaterials is explored.

An area-selective deposition method was developed for CNT and carbon-coated iron nanoparticles. By utilizing organic functionalization the properties of the nanomaterials were tuned, with the purpose to make them soluble in a liquid solvent and also enable them to selectively adsorb to non-polar surfaces.

The first step of the functionalization process was an acid treatment, to introduce defects in the materials. This method was also used to create defects in so-called carbon nanosheets (CNS). The effect of the defect formation on the electric properties of the graphene-like CNS was studied; it was found that the resistance of the CNS could be reduced to 1/50 by acid treating of the sample. Also, the effect of the created defects on gas adsorption to the surface of the CNS has been investigated. This was done using atomic layer deposition (ALD) of TiO2 on the CNS, and a clear change in nucleation be-havior was seen due to the acid-treatment.

Furthermore, a solution-based new method for fabrication of graphene was developed; this method combines intercalation of bromine into graphite with ultrasonic treatment to exfoliate flakes into a solvent. From the solvent the flakes can be deposited onto an arbitrary substrate. Several important parameters in the method were investigated in order to optimize the process. One important parameter proved to be the choice of solvent in all steps of the procedure; it was shown to influence sonication yield, flake size, and deposition results. Toluene was identified as a suitable solvent. A mild heat-treatment of the starting material was also identified as a way to increase the exfoliation yield. Using this method, fabrication of few-layer graphene sheets was achieved and areas down to 3 layers in thickness were identified—this is in the very forefront of current solution-based graphene fabrication techniques.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 57 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 704
Keyword
Graphene, Functionalization, Carbon nanotubes, Carbon nanosheets
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-111655 (URN)978-91-554-7696-0 (ISBN)
Public defence
2010-02-12, Å2005, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2010-01-22 Created: 2009-12-18 Last updated: 2011-01-12
2. Metal Oxide Thin Films and Nanostructures Made by ALD
Open this publication in new window or tab >>Metal Oxide Thin Films and Nanostructures Made by ALD
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thin films of cobalt oxide, iron oxide and niobium oxide, and nanostructured thin films of iron oxide, titanium oxide and multilayered iron oxide/titanium oxide have been deposited by Atomic Layer Deposition (ALD). The metal oxides were grown using the precursor combinations CoI2/O2, Fe(Cp)2/O2, NbI5/O2 and TiI4/H2O. The samples were analysed primarily with respect to phase content, morphology and growth characteristics.

Thin films deposited on Si (100) were found to be amorphous or polycrystalline, depending on deposition temperature and the oxide deposited; cobalt oxide was also deposited on MgO (100), where it was found to grow epitaxially with orientation (001)[100]Co3O4||(001)[100]MgO. As expected, the polycrystalline films were rougher than the amorphous or the epitaxial films. The deposition processes showed properties characteristic of self-limiting ALD growth; all processes were found to have a deposition temperature independent growth region. The deposited films contained zero or only small amounts of precursor residues.

The nanostructured films were grown using anodic aluminium oxide (AAO) or carbon nanosheets as templates. Nanotubes could be manufactured by depositing a thin film which covers the pore walls of the AAO template uniformly; free-standing nanotubes retaining the structure of the template could be fabricated by removing the template. Multilayered nanotubes could be obtained by depositing multiple layers of titanium dioxide and iron oxide in the pores of the AAO template. Carbon nanosheets were used to make titanium dioxide nanosheets with a conducting graphite backbone. The nucleation of the deposited titanium dioxide could be controlled by acid treatment of the carbon nanosheets.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 441
Keyword
Inorganic chemistry, Atomic layer deposition, Metal oxide, Nanostructures, Template deposition, Thin films, Oorganisk kemi
Identifiers
urn:nbn:se:uu:diva-8898 (URN)978-91-554-7220-7 (ISBN)
Public defence
2008-06-05, Å 2005, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2008-05-14 Created: 2008-05-14Bibliographically approved

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Grennberg, HelenaJansson, Ulf

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