Fluorinated Amorphous Diamond Like Carbon Films by PECVD

Fluorinated amorphous diamond-like carbon films (a-C:F) were prepared on room-temperature (100) Si substrates using radio frequency plasma enhance chemical vapor deposition (rf PECVD) by varying the ratio of carbon tetrafluoride and methane (CF4:CH4).The films formed were investigated in terms of the surface morphology, chemical composition, microstructure, mechanical properties, and surface free energy by means of atomic force microscopy (AFM), x-ray photoelectron spectrum (XPS), micro-scratch test, nano-indenter test and contact angle measurement. It was observed that with increasing CF4:CH4, the roughness and F content of the a-C:F films increased while the hardness, Young.s modulus and surface energy decreased. The microstructure of the films also changed from diamond-like to graphite-like. The reduction of the film surface energy with varying F content is believed to be mainly due to the change of bonds in the film, i.e., the decrease of -C-CF bond and corresponding increase of .CF, -CF2, as evidenced by XPS results.