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Deposition of Ti-Si-C-Ag nanocomposite coatings as electrical contact material
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-1785-0864
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-2837-3656
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2010 (English)In: Proceedings of the 56th IEEE Holm Conference on Electrical Contacts (HOLM), IEEE , 2010, 288-294 p.Conference paper, Published paper (Other academic)
Abstract [en]

This paper is a brief review of our recent work and a follow up study on nanocomposite coatings comprising nanocrystalline TiC embedded in an amorphous SiC matrix (nc-TiC/a-SiC) with and without Ag additions applied as electrical contacts. These coating materials are deposited at very high deposition rates (>10 μm/h), to meet industrial demands of high productivity. Here we consider Ti-Si-C-Ag nanocomposite coatings with Ag content in the range of 0-22 at.% deposited in a pilot-plant or an industrial deposition system by dc magnetron sputtering from compound targets onto Si(100) and SiO2(100) substrates. The microstructure, electrical, and mechanical properties of the coatings were studied with transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, electrical contact resistance, resistivity, and nanoindentation measurements. Varying the deposition parameters bias and pressure within ranges typical of coating processing had no effect on the structure. A variation was, however, observed for the contact resistance, that was determined to be in the range 400-900 mΩ at a contact force between 1.9-2.65 N. The coatings with highest Ag content had the lowest contactresistance.

Place, publisher, year, edition, pages
IEEE , 2010. 288-294 p.
Series
Conference on Electrical Contacts (HOLM), ISSN 1062-6808 ; 56
Keyword [en]
Nanocomposite; TiSiC coatings; Electrical contacts; Magnetron sputtering; Contact resistance; Electron microscopy
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-72224DOI: 10.1109/HOLM.2010.5619528ISBN: 978-1-4244-8174-3 (print)OAI: oai:DiVA.org:liu-72224DiVA: diva2:458480
Conference
56th IEEE Holm Conference on Electrical Contacts, Charleston, October 4-7
Available from: 2011-11-23 Created: 2011-11-23 Last updated: 2016-08-31Bibliographically approved
In thesis
1. TiC-based nanocomposite coatings as electrical contacts
Open this publication in new window or tab >>TiC-based nanocomposite coatings as electrical contacts
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This Thesis concerns the advanced surface engineering of novel TiC-based nanocomposite and AgI electrical contact materials. The objective is to make industrially applicable coatings that are electrically conductive and wear-resistant, and have a low coefficient of friction. I have studied electrical contact systems consisting of a Cu substrate with a Ni diffusion barrier and loading support, and a conductive top coating. The contact systems were characterized by x-ray diffraction and photoelectron spectroscopy, analytical electron microscopy, ion beam analysis, nanoindentation, resistivity, and contact resistance measurements. Nc-TiC/a-C/SiC nanocomposite coatings consisting of nanocrystalline (nc) TiC embedded in an amorphous (a) matrix of C/SiC were deposited by magnetron sputtering with rates as high as 16 μm/h. These coatings have a contact resistance comparable with Ag at high loads (~800 N) and a resistivity of 160-770 μΩcm. The electrical properties of the contact can be improved by adding Ag to make nc-Ag/nc-TiC/a-SiC nanocomposites. It is possible to tailor the size and distribution of the Ag grains by varying the fraction of amorphous matrix, so as to achieve good conductivity in all directions in the coatings. Ti-Si-C-Ag coatings have a contact resistance that is one magnitude larger than Ag at lower loads (~1 N), and a resistivity of 77-142 μΩcm. The conductivity of the matrix phase can be increased by substituting Ge, Sn or Cu for Si, which also reduces the Ag grain growth. This yields coatings with a contact resistance twice as high as Ag at loads of 1 N, and a resistivity 274-1013 μΩcm. The application of a conductive top layer of Ag-Pd upon a Ti-Si-C-Ag:Pd coating can further reduce the contact resistance. For barrier materials against Cu interdiffusion, it is shown that conventional electroplating of Ni can be replaced with sputtering of Ni or Ti layers. This is an advantage since both contact and barrier layers can now be deposited in and by the same deposition process. For Ti-B-C coatings deposited by magnetron sputtering, I demonstrate promising electrical properties in a materials system otherwise known for its good mechanical properties. In coatings of low B concentration, the B is incorporated into the TiC phase, probably by enrichment on the TiC{111} planes. The corresponding disturbance of the cubic symmetry results in a rhombohedral TiC:B structure. Finally, it is shown that AgI coatings consisting of weakly agglomerated AgI grains function as solid lubricant on Ag contacts. In an Ag sliding electrical contact, AgI decreases the friction coefficient from ~1.2 to ~0.4. After a few hundred operations, AgI grains have deagglomerated and Ag from the underlying layer is exposed on the surface and the contact resistance decreases to < 100 μΩ.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 63 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1408
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-72228 (URN)978-91-7393-030-7 (ISBN)
Public defence
2011-12-02, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
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Available from: 2011-11-23 Created: 2011-11-23 Last updated: 2016-08-31Bibliographically approved

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Lauridsen, JonasLu, JunEklund, PerHultman, Lars

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