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Water adsorption on fullerene-like carbon nitride overcoats
Carnegie Mellon University.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0001-9402-1491
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.
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2008 (English)In: Thin Solid Films, ISSN 0040-6090, Vol. 517, no 3, 1106-1110 p.Article in journal (Refereed) Published
Abstract [en]

Humidity influences the tribological performance of the head-disk interface in magnetic data storage devices. In this work we compare the uptake of water of amorphous carbon nitride (a-CNx) films, widely used as protective overcoats in computer disk drive systems, with fullerene-like carbon nitride (FL-CNx) and amorphous carbon (a-C) films. Films with thickness in the range 10-300 run were deposited on quartz crystal substrates by reactive DC magnetron sputtering. A quartz crystal microbalance placed in a vacuum chamber was used to measure the water adsorption. Electron paramagnetic resonance (EPR) has been used to correlate water adsorption with film microstructure and surface defects (dangling bonds). Measurements indicate that the amount of adsorbed water is highest for the pure a-C films and that the FL-CNx films adsorbed less than a-CNx. EPR data correlate the lower water adsorption on FL-CNx films with a possible lack of dangling bonds on the film surface. To provide additional insight into the atomic structure of defects in the FL-CNx, a-CNx and a-C compounds, we performed first-principles calculations within the framework of Density Functional Theory. Emphasis was put on the energy cost for formation of vacancy defects and dangling bonds in relaxed systems. Cohesive energy comparison reveals that the energy cost formation for dangling bonds in different configurations is considerably higher in FL-CNx than for the amorphous films. These simulations thus confirm the experimental results showing that dangling bonds are much less likely in FL-CNx than in a-CNx and a-C films.

Place, publisher, year, edition, pages
2008. Vol. 517, no 3, 1106-1110 p.
Keyword [en]
Carbon nitride, CNx, dangling bonds, water adsorption, QCM, EPR, DFT
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-16402DOI: 10.1016/j.tsf.2008.07.022OAI: diva2:139520
Presented at the 35th International Conference on Metallurgical Coatings and Thin Films (ICMCTF), San Diego, USAAvailable from: 2009-01-23 Created: 2009-01-23 Last updated: 2015-03-06Bibliographically approved
In thesis
1. Fullerene-like CNx and CPx Thin Films; Synthesis, Modeling, and Applications
Open this publication in new window or tab >>Fullerene-like CNx and CPx Thin Films; Synthesis, Modeling, and Applications
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This Thesis concerns the development of fullerene-like (FL) carbon nitride (CNx) thin films and the discovery of phosphorus-carbide (CPx) compounds. The work dedicated to CPx include first-principles theoretical simulations of the growth and properties of FL-CPx structures. I have employed DC magnetron sputtering methods to synthesize both CNx and CPx thin films. The deposition conditions for CPx films were chosen on the basis of the theoretical results as well as from the experience from the deposition of FL-CNx thin films.

The characterization of the CPx films is divided into three main directions: structural characterization by transmission electron microscopyand scanning electron microscopy, analysis of the amount of elements and chemical bonds presentin the structure by X-ray photoelectron spectroscopy and Auger spectroscopy, and mechanicalproperty analysis by nanoindentation. The CPx films exhibit a short range orderedstructure with FL characteristics for substrate temperature of 300 °C and for a phosphorus content of 10-15 at.%, which isconsistent with the theoretical findings. These films also displayed the best mechanical properties in terms of hardness and resiliency, which are better than those of the corresponding FL-CNx films.

For the FL-CNx thin film material, I find that the surface water adsorption is lower compared to commercial computer hard disk top coatings. Following that line the dangling bonds in FL-CNx coatings have been investigated  by electron spin resonance (ESR). The absence of ESR signal for FL-CNx indicates very low density of dangling bonds in the material, which explains the low water adsorption tendency.

The potential for using highly elastic FL-CNx coatings in an automotive valve-train environment has also been investigated. CNx coatings of different nitrogen content were investigated using microscopy, wear testing, nanoindentation testing, and in an experimental cam-tappet testing rig. The FL-CNx coating with the higher value of hardness/elastic modulus showed greater durability in cam-tappet wear testing.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 60 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1247
Phosphorus-carbide (CPx), carbon nitride (CNx), thin films, resilient coatings, magnetron sputtering, theoretical modeling
National Category
Other Engineering and Technologies not elsewhere specified
urn:nbn:se:liu:diva-17126 (URN)978-91-7393-676-7 (ISBN)
Public defence
2009-03-30, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2009-03-24 Created: 2009-03-06 Last updated: 2009-03-24Bibliographically approved

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