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Microstructure, mechanical properties, and wetting behaviorof Si-C-N thin films grown by reactive magnetron sputtering
Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
Frederick Seitz Materials Research Laboratory, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, USA.
Thin Film Electronics AB, A°gatan 29, S-582 22 Link¨oping, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
2001 (English)In: Surface and Coatings Technology, ISSN 0257-8972, Vol. 141, no 2-3, 145-155 p.Article in journal (Refereed) Published
Abstract [en]

Silicon–carbon–nitride (Si–C–N) thin films were deposited by reactive magnetron co-sputtering of C and Si targets in a mixed Ar/N2 discharge. Films were grown to a thickness of more than 0.5 μm on graphite and Si(001) substrates held at a negative floating potential of −35 V, and substrate temperature between 100 and 700°C. The total pressure was constant at 0.4 Pa (3 mtorr), and the nitrogen fraction in the gas mixture was varied between 0 and 100%. As-deposited films were analyzed with respect to composition, state of chemical bonding, microstructure, mechanical properties, and wetting behavior by Rutherford backscattering spectroscopy (RBS), energy dispersive spectroscopy (EDS), X-ray photoelectron spectrometry (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nanoindentation and contact angle measurements, respectively. Depending on the deposition condition, ternary SixCyNz films within the composition range 1≤x≤34 at.%, 34≤y≤81 at.%, and 16.5≤z≤42 at.% were prepared with a textured, amorphous-to-graphite-like microstructure. For Si–C–N films with low Si content, C---C, C---N and Si---C bonds were present. At higher Si content, N preferentially bonds to Si, while less C---N bonds were observed. Films containing more than 12 at.% of Si contained widely dispersed crystallites, 2–20 nm in diameter. Incorporation of a few at.% Si resulted in a dramatic reduction of the film surface energy compared to pure CN films. The measured contact angles using distilled water and glycerol liquids were for some films comparable with those on a polytetrafluoroethylene (PTFE), Teflon® surface. The hardness of Si–C–N films could be varied over the range 9–28 GPa.

Place, publisher, year, edition, pages
Elsevier , 2001. Vol. 141, no 2-3, 145-155 p.
Keyword [en]
Silicon-carbon-nitride thin films; Magnetron sputtering; Properties
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-19703DOI: 10.1016/S0257-8972(01)01236-1OAI: diva2:227657
Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2009-07-16Bibliographically approved
In thesis
1. Carbon Nitride: Characterization and Protein Interactions
Open this publication in new window or tab >>Carbon Nitride: Characterization and Protein Interactions
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns synthesis and characterization of carbon-based materials and theinvestigation of the possible use, of a selection of these materials, in biomedicalapplications. Protein adsorption and blood plasma tests were used for this purposeutilizing a surface sensitive technique called spectroscopic ellipsometry.

The materials were synthesized by physical vapor deposition and characterizedregarding microstructure, mechanical properties and optical properties. The ternaries BC-N and Si-C-N as well as carbon and carbon nitrides (CNx) of different microstructureshave been examined. In the B-C-N work, the intention was to investigate the possibilityto combine the two materials CNx and BN, interesting on their own regarding highhardness and extreme elasticity, to produce a material with even better properties.Theoretical calculations were performed to elucidate the different element substitutionsand defect arrangements in the basal planes promoting curvature in the fullerene-likemicrostructure. The Si-C-N ternary was investigated with the consideration of finding away to control the surface energy for certain applications. Amorphous carbon and threemicrostructures of CNx were analyzed by spectroscopic ellipsometry in the UV-VIS-NIRand IR spectral ranges in order to get further insight into the bonding structure of thematerial.

In the second part of this work focus was held on studies of macromolecularinteractions on silicon, carbon and CNx film surfaces using ellipsometry. One purposewas to find relevance (or not) for these materials in biological environments. Materials for bone replacement used today, e.g. stainless steel, cobalt-chromium alloys andtitanium alloys suffer from corrosion in body fluids, generation of wear particles inarticulating systems, infections and blood coagulation and cellular damage leading toimpaired functionality and ultimately to implant failure. Artificial heart valves made ofpyrolytic carbon are used today, with friction and wear problems. Thus, there is still aneed to improve biomaterials. The aim of the fourth paper was to investigate theinteraction between carbon-based materials and proteins. Therefore, amorphous carbon(a-C), amorphous (a), graphitic (g) and fullerene-like (FL) CNx thin films were exposedto human serum albumin and blood plasma and the amount of protein was measured insitu using spectroscopic ellipsometry. Surface located and accessible proteins after blood plasma incubations were eventually identified through incubations in antibody solutions.

Antibody exposures gave indications of surface response to blood coagulation,complement activation and clotting. The a-C and FL-CNx films might according to theresults have a future in soft tissue applications due to the low immuno-activity, whereasthe g-CNx film possibly might be a candidate for bone replacement applications.

"Layered" structures of fibrinogen, a fibrous but soft protein involved in manyprocesses in our body, were grown in situ and dynamically monitored by ellipsometry inorder to understand the adsorption process and molecule arrangement onto a siliconsurface.

In the last paper of this thesis, the effects of ion concentration and proteinconcentration on the refractive index of water-based solutions used in in situ ellipsometrymeasurements were demonstrated and spectral refractive index data for water solutionswith different ionic strengths and protein concentrations have been provided.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 67 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1263
National Category
Natural Sciences
urn:nbn:se:liu:diva-19710 (URN)978-91-7393-593-7 (ISBN)
Public defence
2009-08-28, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2013-10-14Bibliographically approved

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