Room temperature relaxation of freestanding nanocrystalline gold films

We present a novel experimental technique to study compound stress-strain relaxation of thin freestanding gold films at room temperature. The films were 125 nm thick with an average grain size of 50-60 nm. Both static experiments and time-dependent relaxation experiments were performed inside a field emission scanning electron microscope using a micro- electromechanical system (MEMS)-based test bed which is only 3 mm × 10 mm in size. The thin film specimens used in these experiments are co-fabricated with the micromechanical loading device and hence do not need to be externally aligned and gripped. We observed a significant effect of stress relaxation on Young's modulus of gold thin films and modeled the relaxation behavior using a three-parameter standard anelastic solid. The freestanding nature of the thin film also provides us with information about the mechanical behavior of thin films without any substrate effects.