Preparation of superhard amorphous carbon films with low internal stress

Tetrahedral amorphous carbon (ta-C) films were prepared by pulsed laser deposition using a 248-nm excimer laser wavelength and up to 45 J/cm 2 laser pulse energy fluence. Fluences above 6 J/cm 2 and mean kinetic energies of the ablated species above 30 eV, respectively, as well as substrate temperatures below 100 °C were found to be necessary for the formation of ta-C films with high sp 3 percentage. Such films are completely amorphous and have up to 85% sp 3 bonds. As-deposited films show high compressive stresses in the range of 8–10 GPa. The possibilities to reduce those stresses by means of thermal and pulsed laser annealing were investigated. We found that both methods allow the preparation of nearly stress-free diamond-like carbon films with several micrometers of thickness and good adherence to Si and WC hard metal substrates. The Vickers microhardness of those films was measured to be 55–65 GPa and the Young's modulus was measured to be 800–900 GPa by using a dynamic indentation method.