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A study of the process pressure influence in reactive sputtering aiming at hysteresis elimination
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
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2013 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 232, 357-361 p.Article in journal (Refereed) Published
Abstract [en]

Reactive sputtering processes operating at different argon pressures (ranging from 0.3 to 2.7 Pa) have been studied for a number of gas/metal target combinations (Al, Mg, Y in Ar/O-2 and Ti in Ar/N-2). To transcend local deposition conditions, experiments were performed in three different deposition systems. Both experiments and process modeling show the existence of conditions where the hysteresis width may be significantly decreased or even be totally eliminated. This behavior is pronounced for low reactivity gas/metal target combinations such as Al/O-2 and Ti/N-2. It is suggested that for such gas/metal target combinations the direct ion implantation of the reactive gas will be the dominating poisoning mechanism at low total pressure. At elevated total pressure, however, this will no longer be the case. Here, the chemisorption may dominate. For chemisorption-dominated processes, it has been shown earlier that low reactivity materials will exhibit small hysteresis widths and sometimes also be hysteresis free. For materials like Mg and Y, the effect was, as expected, small due to the high affinity of oxygen for these metals.

Place, publisher, year, edition, pages
2013. Vol. 232, 357-361 p.
Keyword [en]
Reactive sputtering, Hysteresis, Elevated pressure, Modeling
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-214001DOI: 10.1016/j.surfcoat.2013.05.035ISI: 000327691300047OAI: oai:DiVA.org:uu-214001DiVA: diva2:683799
Available from: 2014-01-06 Created: 2014-01-06 Last updated: 2014-09-08Bibliographically approved
In thesis
1. Sputtering and Characterization of Complex Multi-element Coatings
Open this publication in new window or tab >>Sputtering and Characterization of Complex Multi-element Coatings
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thin film technology is of great importance in modern society and is a key technology in wide spread applications from electronics and solar cells to hard protective coatings on cutting tools and diffusion barriers in food packaging. This thesis deals with various aspects of thin film processing and the aim of the work is twofold; firstly, to obtain a fundamental understanding of the sputter deposition and the reactive sputter deposition processes, and secondly, to evaluate sputter deposition of specific material systems with low friction properties and to improve their performance.From studies of the reactive sputtering process, two new methods of eliminating the problematic and undesirable hysteresis effect were found. In the first method it was demonstrated that an increased process pressure caused a reduction and, in some cases, even elimination of the hysteresis. In the second method it was shown that sufficiently high oxide content in the target will eliminate the hysteresis.

Further studies of non-reactive magnetron sputtering of multi-element targets at different pressures resulted in huge pressure dependent compositional gradients over the chamber due to different gas phase scattering of the elements. This has been qualitatively known for a long time but the results presented here now enable a quantitative estimation of such effects. For example, by taking gas phase scattering into consideration during sputtering from a WS2 target it was possible to deposit WSx films with a sulphur content going from sub-stoichiometric to over-stoichiometric composition depending on the substrate position relative the target.

By alloying tungsten disulphide (WS2) with carbon and titanium (W-S-C-Ti) its hardness was significantly increased due to the formation of a new titanium carbide phase (TiCxSy). The best sample increased its hardness to 18 GPa (compared to 4 GPa for the corresponding W-S-C coating) while still maintaining a low friction (µ=0.02) due to the formation of easily sheared WS2 planes in the wear track. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 74 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1162
thin film, coating, magnetron sputtering, modelling, tribofilm, tungsten disulphide
National Category
Other Physics Topics
urn:nbn:se:uu:diva-229207 (URN)978-91-554-8997-7 (ISBN)
Public defence
2014-09-26, Polhemsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Swedish Foundation for Strategic Research , 30003
Available from: 2014-09-02 Created: 2014-08-05 Last updated: 2014-09-08

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