Thermal-Piezoresistive Tuning of the Effective Quality Factor of a Micromechanical Resonator

We study the thermal-piezoresistive pumping mechanism within silicon micromechanical resonators. We develop a multiphysics finite-element model to predict the effective quality factor tuning from pumping for arbitrary geometries and dopants. Our model reproduces the effective quality factor tuning direction and magnitude of our fabricated devices versus direct current as a function of dopant type, concentration, thermal actuator width, and device orientation. We show that, in contrast to degenerate parametric amplification, thermal pumping steepens the phase slope near resonance with an increasing effective quality factor.