Determining the Area of Diamond-Like Carbon Film Defects by the Cathodic Polarization

The area of Diamond-like carbon film defects was determined by cathodic polarization. When films cathodically polarized at a potential of -0.8V vs. Ag/AgCl in aerated aqueous Na2SO4 solution, the reduction of oxygen dissolved in the solution took place on the substrate of film defects. The limiting diffusion current of oxygen reduction was proportional to electrode area, so that the area of the film defects could be determined from cathodic current. Although this method is applicable only to insulating films, it has the advantage that it does not damage the substrate. The number, size and distribution of film defects were obtained by Cu electroplating.