Tribological and mechanical properties of carbon nitride films deposited by ionised magnetron sputtering

Tribological and mechanical properties were evaluated for carbon nitride films deposited by an ionised d.c. magnetron sputtering system in which an inductive plasma was generated between the graphite target and the substrate. Steady-state mean coefficients of friction against hard steel in ball-on-rotating disc tests were from 0.44 to 0.81 for films deposited with the inductive plasma, and from 0.36 to 0.60 without the inductive plasma. In each case, the friction increased with increasing nitrogen content in the sputtering gas and then reached a constant value. The elastic modulus of the films was deduced from nanoindentation experiments, and the residual strains in the films were estimated from specimen curvature measurements. The modulus of the films with no inductive plasma reached a maximum with 10vol.% nitrogen in the sputtering gas, and decreased markedly with the inductive plasma. The modulus also decreased at higher pressures and higher substrate bias voltages. The strains in the films were always compressive, and increased when nitrogen was present in the sputtering gas.