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Recovery of electrical resistance in copper films on PET subjected to a tensile strain
For flexible electronics applications it is important to understand the behavior of electrical resistance of metal films on polymer substrates under applied tensile strain. Although the growth of resistance during tensile loading was investigated in a number of research papers, the recovery of resistance during unloading remains virtually unexplored. In this paper, substantial recovery (decrease) of electrical resistance during and after unloading is demonstrated for copper films on polyethylene terephthalate (PET) substrates subjected to a tensile strain with different peak values. Particularly, the films strained to 5% exhibit full resistance recovery after unloading despite clearly visible plastic deformation of the film. The recovery of electrical resistance in connection with the mechanical behavior of film/substrate couple are discussed with the help of in-situ scanning electron microscopy and x-ray diffraction analysis.