Abstract
To investigate vacuum effects on the mechanisms and strength of fatigue crack initiation in submicron-thick freestanding copper (Cu) films, fatigue experiments were conducted on roughly 500-nm-thick freestanding Cu film specimens with a single side edge notch inside a field emission scanning electron microscope (FESEM). Grain boundary and twin boundary ahead of the notch were identified by electron backscatter diffraction (EBSD) analyses. The fatigue damage formation process was observed by FESEM. Experimental results showed that an intrusion/extrusion as the first fatigue damage was formed near a notch root along a Σ3 twin boundary. The first fatigue damage grew with increasing number of cycles and the second fatigue damage was formed ahead of the first fatigue damage. The fatigue crack initiated at the first fatigue damage, and the crack then propagated through the second fatigue damage.
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