Strain gradients in Al-2% Cu thin films

The strain gradient through the thickness of 0.5-, 1.0-, and 2.0-mm-thick Al-2% Cu films on oxidized (001) Si wafers has been examined by using glancing-angle x-ray diffraction to measure the d spacing as a function of penetration depth of the incident x-ray beam. Samples with and without a 1-μm sputtered quartz passivation layer were examined. The only gradient observed in these samples corresponded to surface relaxation in the unpassivated samples at depths of less than 50 Å. This result was verified by examining the shape of the diffraction peaks. The dislocation densities of the films were also determined from the peak shape.