Effects of Cu layers on the deformation behavior of CuTa/Cu multilayer thin films

Nanoindentation and electron microscope techniques are performed on sputtering deposited mono layered nanocrystalline CuTa and multilayered CuTa/Cu thin films. Nanoindentation hardness, microstructural features and surface morphologies of residual indentation are systematically evaluated. For selected samples, the addition of thin Cu layers could inhibit shear bands propagation. The ability of Cu layer to inhibit the propagation of shear bands is sensitive to its structure, which is closely related to the structure of CuTa layer. Further, by adding Cu layers, both strengthening and softening effects are observed in CuTa/Cu thin films with different Ta content but same Cu layer thickness. Based on experimental results, dominant deformation mechanisms of CuTa and CuTa/Cu thin films having various Ta content are proposed and discussed.