NETWORK MODIFICATION OF DLC COATINGS TO ADJUST A DEFINED SURFACE-ENERGY

In addition to the well-known properties of diamond-like-carbon (DLC) coatings, the surface tension is a new criterion to characterize this kind of thin films. To influence the surface tension of DLC coatings, their structure is modified by the incorporation of different elements like fluorine or silicon into the matrix of the amorphous network. Fu rthermore, the surface tension can be strongly influenced by the depos ition parameter. With the appropriate reactive gas and process paramet er it is possible to adjust separately the polar and the dispersive co mponents of the surface tension. Using fluorinated hydrocarbons an alm ost PTFE-like coating with a surface tension of 22 mN/m is realized. S ince halogenous monomers are very controversial it is desirable to fin d other reactive gases for modifying the surface tension on the basis of amorphous hydrocarbon layers. First investigations with silicon con taining monomers point out the possibility to prepare hard coatings wi th a surface tension also comparable to PTFE but with a much better mi crohardness of about 15 GPa instead of 6 GPa for fluorinated thin film s or 0.3 GPa for PTFE, respectively. To calculate the surface tension of plasma polymerized thin films, the applicability of contact angle m easurements (sessile-drop method) is investigated first by comparing d ifferent approaches for the adhesion energy and evaluation methods, re spectively.