Elasto-plastic properties of gold thin films deposited onto polymeric substrates

This work examines mechanical properties of 50-300 nm gold thin films deposited onto micrometer-thick flexible polymer substrates by means of tensile testing of the film-substrate system and modeling. The film properties are extracted from mechanical testing of the film-substrate system and modeling of the bimaterial. Unlike materials in bulk geometry, the film elastic modulus and yield strength present an important dependence with film thickness, with modulus and yield strength of about 520 and 30 GPa, respectively, for the thinner films and decreasing toward the bulk value as the film thickness increases. The relation between grain size, film thickness, and yield strength is examined. Finite element analysis provides further insight into the stress distribution in the film-substrate system.