Thin metal films on compliant polymer substrates are of major interest for
flexible electronic technologies. The suitability of a film system for flexible
applications is based on the electro-mechanical performance of the metal
film/polymer substrate couple. This study demonstrates how a 10 nm Cr interlayer
deteriorates the electro-mechanical performance of 50 nm Au films on polyimide
substrates by inducing the formation of cracks in the ductile layer. Combined
in-situ measurements of the film lattice strains with x-ray
diffraction and electrical resistance with four point probe of the Au-Cr and Au
layers during uniaxial straining confirmed different electro-mechanical
behaviours. For Au films with a Cr interlayer the film stress decreases rapidly
as cracking initiates and reaches a plateau as the saturation crack spacing is
reached. Crack formation and stress drop correspond to a rapid increase in the
film resistance. Without the interlayer the Au film stress reaches a maximum
around 2% engineering strain and remains constant throughout the experiment. The
film resistance is unaffected by the applied elongation up to a maximum strain
of 15%, giving no sign of cracking in the metal layer. The outstanding
electro-mechanical performance of the gold film indicates that adhesion layers,
like Cr, may not be necessary to improve the performance of ductile films on
polymers.