Stability of Mechanical Properties for Submicrometer Single-Crystal Silicon Cantilever Under Cyclic Load

The stability of mechanical properties of submicrometer-thick cantilevers was systematically investigated under different conditions: driving force, vacuum, humidity, and temperature. For the submicrometer-thick cantilever, the cyclic test did not lead to failure but resulted in distinguish resonant frequency shift. The frequency shift is caused by fatigue stress, adsorption/desorption, and temperature-induced lever softening effect. At a vacuum of 10^-3 Pa, the stress change makes a dominant contribution to the frequency shift, and the desorption induced lever softening is a secondary factor. The resonant fre quency continuously goes down with the cycles, and this frequency shift increases with the driving force of the lever. At a vacuum of 1 Pa, the resonant frequency is nearly unchanged until 10⁹ cycles. Humid air accelerates water adsorption and dramatically enhances the lever stiffness, resulting in frequency increase. At room temperature, the Q factors of the lever change a little with the cycles in spite of the frequency decrease. At elevated temperature (100°C and 200°C), the frequency and Q factors increase with the cycles due to the dominant desorption.