Mechanical behavior of Pt and Pt-Ru solid solution alloy thin films

The mechanical behavior of Pt and Pt-Ru solid solution alloy thin films was evaluated using wafer curvature and nanoindentation techniques. Films approximately 200 nm thick with nominal compositions of 0, 1, 2, 5, 10, and 20 wt% Ru were prepared by co-sputtering on oxidized Si wafers. For temperatures below approximately 500 degreesC, at which dislocation motion dominates behavior, the elastic modulus, flow stress, and hardness all increase with increasing Ru content. These experimental results were compared to flow stress calculations that are based on existing models for dislocation motion. This analysis indicates that the solid solution strengthening mechanism is a major contributor to the film strengthening. The critical temperature above which diffusion-controlled plasticity dominates is not significantly affected by solute content. Above this temperature, the degree of stress relaxation was dependent on Ru content, which could be attributed to a limit on diffusional relaxation. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.