Strong single-crystalline Au films tested by a new synchrotron technique

Although it is well known that thin films exhibit mechanical properties very different from those of their bulk counterparts, knowledge of the underlying mechanisms is incomplete. Single-crystalline films have a favorable microstructure for investigating the scaling behavior of mechanical properties. We present a novel experimental route for preparing single-crystalline Au films on a compliant polyimide substrate. For such single-crystals, we have developed a synchrotron-based tensile testing technique to measure the isothermal stress–strain curves and average peak widths. The analysis of Laue diffraction patterns as well as a parallel transmission electron microscopy study give new insight in the initial and evolving microstructure of the films. Complex novel deformation mechanisms are found, including a transition of the dominant deformation mechanism from full to partial dislocations in films thinner than 160 nm. The scaling behavior is described in view of the coexistence of different deformation mechanisms where the nucleation stress for single dislocations very likely governs the behavior.