The mechanical behavior of nanoporous gold thin films

Thin films of nanoporous noble metals exhibit an interconnected, porous structure with ligament widths and pores on the order of 10 nm or higher. In this study, thin film stress measurements and in-situ nanoindentation in a transmission-electron microscope were performed to investigate the effects of nanoscale geometric confinement on the mechanicalproperties of metals and on dislocation-mediated plasticity. Although somefilms exhibit macroscopic cracking, the deformation of individual ligaments is completely ductile and clearly involves dislocation activity even in 10 nm wide ligaments. The stresses generated in these films during thermal cycling correspond to bulk stresses that approach the theoretical strength of the metal. Film stress exhibits a dependence on film thickness, even though the ligament width is much smaller and would presumably govern deformation.