Size-dependent rate sensitivity and plasticity of nanocrystalline Ru films

The rate sensitivity of hexagonal close-packed nanocrystalline Ru films was investigated by nanoindentation, which is found to be a function not only of grain size but also of indentation depth. The enhanced magnitude of the sensitivity is comparable to that of face-centered cubic nanocrystalline metals. Experimental results suggest that the interaction of dislocations with grain boundaries (GBs) and the diffusion along the tip–sample interface are the dominant mechanisms, whereas both GB sliding and Coble creep are ruled out as the rate-controlling deformations.