High frequency dual-mode thermal-piezoresistive oscillators

This work presents high frequency fully-micromechanical self-sustained oscillators. It has previously been demonstrated that interactions between mechanical strain and thermally generated actuation forces in micromechanical structures through the piezoresistive effect, can result in a positive feedback loop leading to self-sustained oscillation without the need for an electronic amplifier. In our previous work we demonstrated self-sustained oscillation of single-crystalline silicon dual-plate structures with frequencies up to 6.7MHz. This work demonstrates higher frequency thermal-piezoresistive self-sustained oscillators with frequencies up to 36MHz using I³-shaped resonant structures. Due to the highly nonlinear (mixed flexural-extensional) deformation of actuator/piezoresistors in such structures, they can provide two dominant output frequency harmonics. The dominant harmonic can be selected by changing the resonator bias current.