ION-BEAM DEPOSITED CARBON NITRIDE FILMS - CHARACTERIZATION AND IDENTIFICATION OF CHEMICAL SPUTTERING

Carbon nitride films were synthesized by ion beam assisted sputtering. A graphite target was sputtered by argon or nitrogen ions and the gro wing film was simultaneously bombarded by a focused nitrogen ion beam of energies between 100-800 eV at 100 and 400 degrees C. It has been f ound that film growth occurs only if the ion-to-atom arrival ratio is smaller than a critical value of about 1.8 and it appears to be almost independent of the assisting beam energy. This effect, limiting the f ilm growth, is a consequence of a chemical reaction between carbon and nitrogen forming volatile CN compounds. Experimental evidence was obt ained by monitoring the gas evolved during the deposition process with a quadrupole gas analyzer. The maximum value of nitrogen content meas ured by Auger electron spectroscopy was about 35 at.%. All films were investigated by Fourier transform infrared spectroscopy and X-ray phot oelectron spectroscopy. The latter technique shows a preferential bond ing of N to sp(3)-hybridized C. Hardness measurements with values up t o 20 GPa were measured using a depth sensing nanoindenter.