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Network modification of DLC coatings to adjust a defined surface energy

: Trojan, K.; Grischke, M.; Dimigen, H.


Physica status solidi. A 145 (1994), No.2, pp.575-585
ISSN: 0031-8965
ISSN: 1862-6300
ISSN: 1521-396X
ISSN: 1862-6319
Journal Article
Fraunhofer IST ()
a-C-H; a-C-H-F; adhesion; contact angle; diamond-like carbon; hydrocarbon; hydrophilic; hydrophope; networkmodification; plasmapolymer; surface energy; surface tension; wettability

In addition to the well-known properties of diamond-like-carbon (DLC) coatings, the surface tension is a new criterion to characterize these kind of thin films. To influence the surface tension of DLC-coatings, their structure was modified by the incorporation of different elements like fluorine or silicon into the matrix of the amorphous network. Furthermore, the surface tension can be strongly influenced by the deposition parameter. With the appropriate reactive gas and process parameter it is possible to adjust seperate the polar and the dispersive component of the surface tension. Using fluorinated hydrocarbons an almost PTFE-like coating with a surface tension of 22mN/m was realized. Since halogenous monomers are very controversial it is wishful to find other reactive gases for modifying the surface tension on the basis of amorphous hydrocarbon layers. First investigations with silicon containing monomers point out the possibility to prepare hard coatings with a surface tension also comparable to PTFE but with a much better micro-hardness of about 15GPa instead of 6GPa for fluorinated thin films or 0.3GPa for PTFE, respectively. To calculate the surface tension of plasma polimerized thin films, the applicability of contact angle measurements (sessile-drop method) was investigated first by comparing different approaches for the adhesion energy and evalation methods, respectively.