Elastic properties of hard TiCxNy films grown by dual ion beam sputtering

The nano-hardness (HV) of TiCxNy (x+y≈1) thin films has been investigated by nano-indentation as a function of the ion beam assistance for different contact depths and annealing temperatures. The hardness at low indentation depths (i.e. 10 nm) is observed to decrease abruptly from 55 down to 26 GPa when the carbon content in the films decreases from x≈0.2 to x≈0.05 (∼TiN). On the contrary, hardness measured at penetration depths of 40 nm is observed to decrease very slightly. After annealing in UHV the hardness of the coatings becomes independent of the penetration depths. Moreover, the values of the hardness of the annealed coatings are similar to the values measured for the untreated coatings at high penetration depths. All this suggests that, the surface of the films are hardened significantly, and that this hardening can be reduced not only by annealing but also by increasing the ion beam bombardment during the growth process. The mechanism of the film hardening has been addressed in terms of the content of lattice defects and its dependence on the ion bombardment.