ION-ASSISTED LASER PROCESSING OF CN(X) FILMS

We have produced CN(x) thin films with x = 0-0.70 by using an ion-assisted laser deposition method. In this method a graphite target was ablated while simultaneously bombarding the substrate with nitrogen ions. The deposition rate, ion current, substrate temperature and substrate bias were varied to enhance nitrogen incorporation and to optimize the properties of the thin films. The films were characterized using Rutherford backscattering-channelling, Auger electron spectroscopy, electron energy loss spectroscopy, transmission and scanning electron microscopy, Raman spectroscopy and nano-indentation hardness measurements. The average nitrogen concentration was found to vary (N/C atomic ratio) in the range 0-0.70. The transmission electron microscopy studies showed that these films were polycrystalline with a fine-grain equiaxed structure (average size 10 nm) above a substrate temperature of 200-degrees-C. The sp3/sp2 ratio was determined to be 25%-30% using electron energy loss spectroscopy. The Raman studies showed two peaks at 1285 and 1575 cm-1 corresponding to sp3 and sp2 bonding respectively. The films exhibited qualitatively very high hardness and thermal annealing resistance.