Mechanical and tribological aspects on a-C films deposited by lamp assisted chemical vapour deposition

A novel approach to deposit amorphous carbon films (a-C) from the precursor CH2I2 at low cost and high efficiency is reported. The radiation of a halogen lamp was used to heat and to photo-dissociate the CH2I2 (g) precursor as well as the substrate surface. The combination of thermal and photolytic effects shows new interesting growth behaviour. Cemented carbide and Si were used as substrates. The films were investigated with respect to hardness and elastic modulus by nanoindention. A ball-on-disc tribometer was used to evaluate the friction and wear of the films in sliding contact against bearing steel. The adhesion between the film and substrate was investigated by Rockwell C indentation. The films were additionally analysed with scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The films showed extremely low surface roughness (Ra<0.7 nm) and were free from micro-voids. The hardness and elasticity was measured to 10 and 70 GPa, respectively. Low friction coefficients in the 0.15-region were measured. No influence of the substrate material on the film properties was found.