Influence of sputtering parameters on the mechanical properties of chromium films

Chromium films were produced on steel substrates by d.c. magnetron sputtering in pure argon at different target power densities applying a negative substrate bias voltage V, from 4 to 1000 V. At the target power density of 4 W cm -2 the residual stresses shifted from tension towards compression while increasing the substrate bias voltage. The compressive stresses increased up to - 1.8 GPa at V 5 = -500 V and then decreased for higher bias values. While increasing the substrate bias, the film microhardness remained constant at first. Beyond a threshold bias value of -150 V, it increased from 4 to 11.5 GPa. The threshold bias value increased with the target power density. This increase of the film microhardness can be correlated with the embedded argon concentration.