Thermoelastic damping in bilayered micromechanical beam resonators

A detailed analysis of thermoelastic damping (TED) is essential in the design of the next generation of layered composite microresonators employed in microelectromechanical systems (MEMS) for sensing and communications. Here, we present an exact theory to compute the frequency dependence of thermoelastic damping in asymmetric, bilayered, micromechanical Euler - Bernoulli beam resonators. Comparison of the computed values for thermoelastic damping with previously measured internal friction in Au/SiO2 microcantilevers suggests that TED contributes significantly to damping at higher modes and frequencies (similar to 1 MHz), but is negligible at lower frequencies, in these structures. The utility of the theory for MEMS design is illustrated by considering the representative example of Al/SiC bilayered microresonators.