Hydrogen-Free Tetrahedral Carbon (Ta-C) Films Preparation and Tribological Characterisation

摘要

Amorphous carbon containing very little hydrogen and having a highly tetrahedral structure is deposited by the Filtered Cathodic Vacuum Arc (FCVA) technique. The tribological properties of these films were determined by an ultra low load depth sensing nanoindenter to examine their dependence on the carbon ion energy. An optimum ion energy around 80 to 90 eV has been found, which coincides with the energy at which the sp{sup}3 content and film density reach maximum values. At this ion energy, the hardness, modulus and critical load of a 60 nm film on sapphire exhibit maximum values of 60 GPa, 580 GPa and 7 mN, respectively. The frictional coefficient shows a minimum of 0.16. The use of both continuous stiffness technique and sapphire substrates registered an improvement of 43% and 68% in hardness and modulus values, respectively, over the same film on silicon by using a normal loading and unloading indentation technique. The modulus to hardness ratio of close to 10 for our samples confirms that there is a great improvement in the modulus measurement.