FORMATION OF CARBON NITRIDE FILMS BY HIGH-ENERGY NITROGEN ION-IMPLANTATION INTO GLASSY-CARBON

Carbon nitride beta-C3N4 thin films are presently attracting increasin g interest both scientifically and technologically. This is due to the ir expected mechanical and tribological properties, superior to those of diamond. In the present work the nitriding process of the near-surf ace region of glassy carbon by high-energy nitrogen ion implantation h as been investigated with particular emphasis on the implantation temp erature and post-annealing processes. The implantations were performed at room temperature and at 400 degrees C using 25 and 50 keV nitrogen ions up to doses of 1 x 10(18) cm(-2). The distribution of the implan ted nitrogen and its bonding states have been studied by a number of c omplementary techniques: Auger electron spectroscopy, secondary ion ma ss spectrometry and X-ray photoelectron spectroscopy (XPS). The possib ility of carbon nitride phase formation and the effect of implantation on the glassy carbon microstructure was assessed by Raman measurement s. Volume effects were studied by measurements of the step height betw een the implanted and unimplanted regions. The maximum amount of nitro gen in the implanted layer obtained in the present study reaches 25-30 at.%. Annealing the RT implanted layer up to 500 degrees C does not r esult in a measurable diffusion of the implanted nitrogen. However, du ring annealing to 1000 degrees C a diffusion of the implanted nitrogen occurs. Hot implantation at 400 degrees C results in a broad and near ly homogeneous distribution of the implanted nitrogen with an average concentration of 18 at.%. XPS measurements indicate that hot implantat ion results in a preferred population of a rather covalent nitrogen bo nding state in the implanted layer compared with that obtained after R T implantation and annealing.