Structure, composition and tribological properties of carbon nitride films

Carbon nitride (CNx) films were synthesized using reactive magnetron sputtering of a high purity graphite target under argon/nitrogen atmosphere using various substrates held at the temperature below 453 K. Typically, the films were grown at the rate of 0.025 mu m x min(-1) to obtain a total thickness of 2.0 mu m. The analyses of chemical composition made by Rutherford Backscattering Spectroscopy (RBS) and Energy Dispersive X-ray Analysis (EDAX) showed that the maximum amount of nitrogen introduced to the films is equal to 37 at.%. The Raman-spectra and Atomic Force Microscopy (AFM) analyses show that CNx films have an amorphous structure and replicate the substrate topography, giving rise to surface roughness equal to or better than the original substrate. The hardness measurements showed microhardness of the films up to 22 GPa. Good adhesion (L-c > 80 N) was obtained after applying a metallic interlayer and a substrate bias voltage of -300 V d.c. The unlubricated ball-on-disc tribotesting of the CNx films showed that a friction coefficient against bearing steel was equal to 0.45 and good wear resistance was achieved for the sample made with a substrate bias voltage of -300 V d.c. The paper presents investigation results and a discussion regarding the influence of argon/nitrogen atmosphere composition and substrate bias voltage on the properties of CNx films. (C) 1998 Elsevier Science S.A.