Multiscale analysis on the onset of nanoindentation-induced delamination: Effect of high-modulus Ru overlayer

This paper provides atomistic level findings regarding interfacial crack nucleation and propagation processes. To see the Cu/SiO2Cu/SiO2 cracking, we carried out nanoindentations in the Ru/Cu/SiO2Ru/Cu/SiO2 system using an atomistic/continuum coupling method. We found that interfacial crack nucleation is triggered by heterogeneous dislocation nucleation. The resulting buckling delamination mode is qualitatively similar to that observed experimentally. In addition, comparison with the nanoindentation in the Cu/SiO2Cu/SiO2 system demonstrates that nanoindentation testing utilizing the high-modulus Ru overlayer is an effective probe for evaluating Cu film delamination. In the system with the Ru overlayer, the crack propagates along the interface in a brittle manner once the crack nucleates. On the other hand, without the Ru overlayer, crack propagation is significantly retarded and less driven, which is attributed to a large number of plastic events in the Cu film during loading. These results would provide a clear physical picture for explaining the experimental results.