On the presence of molecular nitrogen in nitrogen-implanted amorphous carbon

摘要

Hard amorphous carbon (ta-C) films were implanted with 20 keV N+ ions into saturation at two different temperatures. Monitoring the composition ratio N/C using in situ elastic recoil detection analysis, saturation levels N/C of 0.35 and 0.16 have been found for implantations at room temperature and 400 degrees C, respectively. Raman and x-ray photoelectron spectroscopy analyses of the implanted films indicate the presence of N-2 molecules inside room-temperature implanted samples, but not for the case of implantation at 400 degrees C, Cross-section transmission electron microscopy images show the presence of near-surface voids, interpreted as remnants of Nz-filled bubbles, in the former case. Annealing experiments show that about 50 of the total N inventory consists of nitrogen only weakly trapped inside the carbon matrix in room-temperature implanted films, this fraction being significantly reduced in samples held at 400 degrees C during implantation. (C) 1997 American Institute of Physics.