Study of creep/relaxation mechanisms in thin freestanding nanocrystalline palladium films through the lab-on-chip technology

A nanomechanical lab-on-chip set-up has been used to study the creep/relaxation response of thin palladium films with temperature. The basic idea is to use residual stresses present in a silicon nitride thin beam to load the test film after etching the underneath sacrificial layer. The main advantage of this experimental method is that we can simultaneously perform thousands of creep/relaxation tests without monopolizing any external actuating/loading equipment and without using any time consuming calibration procedures. A signature of the dominant relaxation mechanism is given by the activation volume which has been determined for different levels of plastic deformation and different temperatures. The activation volume is equal to ∼15-40 b³ at room temperature and tends to decrease with increasing plastic deformation. The activation volume decreases when relaxation takes place at 50 °C down to ∼7-20 b³. These variations of the activation volume indicate the competition between two different thermally activated deformation mechanisms in the temperature range between 20 °C and 50 °C.