The adhesion of hydrogenated amorphous carbon films on silicone

A number of hydrogenated amorphous carbon films, the properties of which were varied by adjusting the RF power, were deposited from a 13-56-MHz plasma onto silicone and glass substrate's. Deposition was monitored by in situ ellipsometry performed on the glass substrates and the refractive index was used as a figure of merit for each film. Film adhesion was measured by a pull adhesion technique and films were found to have adhesion of 12 MPa, except in a region (1.75 < n < 1.83) where the adhesion was 20 MPa. No link was observed between adhesion and surface morphology or roughness; however, the increase in adhesion was accompanied by a change in the Raman spectrum. In the higher refractive index (greater than or equal to 1.88), lower adhesion (approximate to 12 MPa) films, the G- and D-bands are evident in the Raman spectra. However, in the lower refractive index (less than or equal to 1-83), higher adhesion (approximate to 20 MPa) films, the Raman spectra are dominated by a featureless fluorescence background, with no G- or D-bands evident. The higher adhesion of the lower refractive-index films is combined with a low friction that makes these films ideal for overcoming the inherent tackiness of silicone and may provide suitable coatings for biomedical applications. (C) 2001 Elsevier Science B.V. All rights reserved.