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Electronic structure and chemical bonding of amorphous chromium carbide thin films
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
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2012 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 24, no 22, 225004- p.Article in journal (Refereed) Published
Abstract [en]

The microstructure, electronic structure and chemical bonding of chromium carbide thin films with different carbon contents have been investigated with high-resolution transmission electron microscopy, electron energy loss spectroscopy and soft x-ray absorption-emission spectroscopies. Most of the films can be described as amorphous nanocomposites with non-crystalline CrCx in an amorphous carbon matrix. At high carbon contents, graphene-like structures are formed in the amorphous carbon matrix. At 47 at.% carbon content, randomly oriented nanocrystallites are formed creating a complex microstructure of three components. The soft x-ray absorption-emission study shows additional peak structures exhibiting non-octahedral coordination and bonding.

Place, publisher, year, edition, pages
2012. Vol. 24, no 22, 225004- p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-177220DOI: 10.1088/0953-8984/24/22/225004ISI: 000304873300006OAI: oai:DiVA.org:uu-177220DiVA: diva2:540936
Available from: 2012-07-12 Created: 2012-07-04 Last updated: 2015-07-07Bibliographically approved
In thesis
1. Synthesis and Characterization of Amorphous Carbide-based Thin Films
Open this publication in new window or tab >>Synthesis and Characterization of Amorphous Carbide-based Thin Films
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, research on synthesis, structure and characterization of amorphous carbide-based thin films is presented. Crystalline and nanocomposite carbide films can exhibit properties such as high electrical conductivity, high hardness and low friction and wear. These properties are in many cases structure-related, and thus, within this thesis a special focus is put on how the amorphous structure influences the material properties.

Thin films within the Zr-Si-C and Cr-C-based systems have been synthesized by magnetron sputtering from elemental targets. For the Zr-Si-C system, completely amorphous films were obtained for silicon contents of 20 at.% or higher. Modeling of these films, as well as experimental results suggest that the films exhibit a network-type structure where the bond types influence the material properties. Higher hardness and resistivity were observed with high amounts of covalent Si-C bonds.

Several studies were performed in the Cr-C-based systems. Cr-C films deposited in a wide composition range and with substrate temperatures of up to 500 °C were found to be amorphous nanocomposites, consisting of amorphous chromium carbide (a-CrCx) and amorphous carbon (a-C) phases. The carbon content in the carbidic phase was determined to about 30-35 at.% for most films. The properties of the Cr-C films were very dependent of the amount of a-C phase, and both hardness and electrical resistivity decreased with increasing a-C contents. However, electrochemical analysis showed that Cr-C films deposited at higher substrate temperature and with high carbon content exhibited very high oxidation resistance. In addition, nanocomposite films containing Ag nanoparticles within an amorphous Cr-C matrix were studied in an attempt to improve the tribological properties. No such improvements were observed but the films exhibited a better contact resistance than the corresponding binary Cr-C films. Furthermore, electrochemical analyses showed that Ag nanoparticles on the surface affected the formation of a stable passive film, which would make the Cr-C/Ag films less resilient to oxidation than the pure Cr-C films.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 63 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1239
Amorphous, coating, thin film, nanocomposite, sputter deposition, PVD, XPS, SEM, TEM, electrical properties, mechanical properties
National Category
Inorganic Chemistry
urn:nbn:se:uu:diva-247282 (URN)978-91-554-9198-7 (ISBN)
Public defence
2015-05-08, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Available from: 2015-04-16 Created: 2015-03-16 Last updated: 2015-07-07

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