STUDY OF NITROGEN-IMPLANTED AMORPHOUS HYDROGENATED CARBON THIN-FILMS BY VARIABLE-ENERGY POSITRON-ANNIHILATION SPECTROSCOPY

Hard amorphous hydrogenated carbon (a-C:H) films deposited by self-bia s glow discharge were implanted at room temperature with 70 keV nitrog en ions at fluences between 2.0 and 9.0x10(16) N/cm(2). The implanted samples were analyzed by positron Doppler broadening annihilation spec troscopy to determine the voids distribution. For samples implanted wi th 2.0X10(16) N/cm(2) the defect distribution is broader than the vaca ncies depth profile predicted by Monte Carlo simulation. For higher fl uences we observed a reduction of the defect density. These results ar e discussed in terms of a competition between two processes: ion induc ed defects and structural modifications induced in the films due to io n implantation. (C) 1997 American Institute of Physics.