PECVD OF HARD AND ELASTIC BCN COATINGS

Compounds of the B-C-N system are very promising to produce superhard coatings with good tribological, chemical and thermal properties. Consequently, BCN films were prepared by plasma enhanced chemical vapor deposition (PECVD). The films were deposited from gaseous mixtures of BCl3-C2H4-N2-H2-Ar in different unipolar and bipolar pulsed glow discharges at 550G and analyzed with respect to composition, electronic structure and mechanical properties. The microstructure and composition of the BCN films were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and reflection electron en- ergy loss spectroscopy (REELS). Mechanical properties were characterized using both the traditional Vickers method and nanoindentation. The films, that were deposited using a bipolar pulsed generator, were weak and had a sponge-like structure, whereas the films prepared using an unipolar generator were well adherent, had a hardness of more than 11GPa and very high elastic recoveries of up to 80%. The elasticity properties supposedly result from the formation of a fullerene-like structure.