Study of surface energy of tetrahedral amorphous carbon films modified in various gas plasma

Although tetrahedral amorphous carbon (ta-C) films exhibit many superior qualities, by modifying the ta-C films, it would be able to fulfil the requirements for an even wider range of applications. This study aims to investigate the changes in terms of wettability of surface treated ta-C films by subjecting them to different gas plasma (Ar, O-2, CF4 and H-2) surface treatment with varied duration and flow rate. Gas plasma surface treatment can change the surface properties of the ta-C films while retaining their inherent properties. Video contact analyzer (VCA), Atomic force microscope (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterise properties of the treated surface. It has been observed that the plasma treatment with Ar, O-2 and H-2 causes the SE of the ta-C film to increase to a higher value and subsequently increases or decreases slightly with treatment duration. Of the three gases investigated, the oxygen treated surface displays the highest SE of 65 dyne/cm, while the as-deposited ta-C film exhibit a SE of 40.8 dyne/cm. Plasma treatment with CF4, however, caused a decrease in SE. The flow rates of the plasma gases also have some effects on the surface energy. The AFM and Raman spectroscopy studies reveal that the surface morphology and structure did not undergo much change by the plasma treatment. (C) 2003 Elsevier Science B.V. All rights reserved.