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On the origin of a third spectral component of C1s XPS-spectra for nc-TiC/a-C nanocomposite thin films
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
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2008 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 15, 3563-3570 p.Article in journal (Refereed) Published
Abstract [en]

X-ray photoelectron spectroscopy (XPS) spectra of sputter-etched nc-TiC/a-C nanocomposite thin films published in literature show an extra feature of unknown origin in the C1s region. This feature is situated between the contributions of carbide and the carbon matrix. We have used high kinetic energy XPS (HIKE-XPS) on magnetron-sputtered nc-TiC/a-C thin films to show that this feature represents a third chemical environment in the nanocomposites, besides the carbide and the amorphous carbon. Our results show that component is present in as-deposited samples, and that the intensity is strongly enhanced by Ar+-ion etching. This third chemical environment may be due to interface or disorder effects. The implications of these observations on the XPS analysis of nanocomposites are discussed in the light of overlap problems for ternary carbon based systems.

Place, publisher, year, edition, pages
2008. Vol. 202, no 15, 3563-3570 p.
Keyword [en]
X-ray photoelectron spectroscopy (XPS), Nanocomposite coatings, Sputtering, Transmission electron microscopy (TEM)
National Category
Inorganic Chemistry
URN: urn:nbn:se:uu:diva-16522DOI: 10.1016/j.surfcoat.2007.12.038ISI: 000255492700016OAI: oai:DiVA.org:uu-16522DiVA: diva2:44293
Available from: 2008-05-28 Created: 2008-05-28 Last updated: 2016-04-26
In thesis
1. Design of carbide-based nanocomposite coatings
Open this publication in new window or tab >>Design of carbide-based nanocomposite coatings
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis research on synthesis, microstructure and properties of carbide-based coatings is reported. These coatings are electrically conducting, and can be tailored for high hardness, low friction and wear, along with load-adaptive behaviour. Tailoring these properties is achieved by controlling the relative phase content of the material. Coatings have been synthesised by dc magnetron sputtering, and their structures have been characterised, mainly by X-ray photoelectron spectroscopy and X-ray diffraction.

It has been shown that nanocomposites comprising of a nanocrystalline transition metal carbide (nc-MeCx, Me = Ti, Nb or V) and an amorphous carbon (a-C) matrix can result in low contact resistance in electrical contacts. Such materials also exhibit low friction and high resistance to wear, making them especially suitable for application in sliding contacts. The lowest contact resistance is attained for small amounts of the amorphous carbon phase.

It has been shown that specific bonding structures are present in the interface between nc-TiCx and the a-C phases in the nanocomposite.  It was found in particular that Ti3d and C2p states are involved, and that considerable charge transfer occurs across the interface, thereby influencing the structure of the carbide.

Further design possibilities were demonstrated for TiCx-based nanocomposites by alloying them with weakly carbide-forming metals, i.e., Me = Ni, Cu or Pt.  Metastable supersaturated solid solution carbides, (T1-xMex)Cy, were identified to result from this alloying process. The destabilisation of the TiCx-phase leads to changes in the phase distribution in the deposited nanocomposites, thus providing further control over the amount of carbon phase formed. Additional design possibilities became available through the decomposition of the metastable (Ti1-xMex)Cy phase through an appropriate choice of annealing conditions, yielding either more carbon phase or a new metallic phase involving Me. This alloying concept was also studied theoretically for all 3d transition metals using DFT techniques.

It has also been demonstrated that Ar-ion etching (commonly used in the analysis of carbide based nanocomposites) can seriously influence the result of the analysis, especially for materials containing metastable phases. This implies that more sophisticated methods, or considerable care are needed in making these analyses, and that many of the earlier published results could well be in error.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 83 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 682
chemistry, thin film, dc magnetron sputtering, carbide, nanocomposite, PVD, solid solution
National Category
Chemical Sciences Inorganic Chemistry
Research subject
Inorganic Chemistry
urn:nbn:se:uu:diva-109427 (URN)978-91-554-7636-6 (ISBN)
Public defence
2009-11-27, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Available from: 2009-11-06 Created: 2009-10-15 Last updated: 2014-01-21Bibliographically approved

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Lewin, ErikSandell, ASiegbahn, HJansson, Ulf
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