Thermoelastic damping dependent quality factor analysis of rectangular plates applying modified coupled stress theory

Abstract

Thermoelastic damping plays an essential role among the different energy dissipation mechanisms and should be minimized in MEMS/NEMS based resonators for enhancing its performance parameters. In this paper, the different performance indices analyzed are quality factor, thermoelastic frequency and figure of merit of the resonator using five different structural materials (polySi, diamond, Si, GaAs and SiC). Figure of merit is the product of quality factor and thermoelastic frequency which should be maximized in order to provide better sensitivity and noise rejection for resonators. As the size of the devices is scaled down, classical continuum theories are not able to explain the size effect related mechanical behaviour at micron or submicron levels and as a result non-classical continuum theories are employed with the inception of internal length scale parameters. Analysis of isotropic rectangular micro-plates based on Kirchhoff model applying M odified Coupled Stress Theory is used to analyze the size-dependent thermoelastic damping and its impact on quality factor and subsequently on Figure of Merit of the resonator. It is found that the QTED of the beams predicted by the non-classical MCST based model are larger than that predicted by the classical beam model. The descending material order in which QTED varies is polySi>Si>diamond>GaAs>SiC. Maximum and minimum ω is achieved for diamond and GaAs respectively. Maximum figure of merit is obtained for polySi with a value of 1.29*1014 and that of minimum is for GaAs (1.77*1011). The material order in which the figure of merit QTED * ωi changes is the same as that for quality factor change and the order in which it varies is PolySi>Diamond>Si>SiC>GaAs. The numerical analysis is done by using MATLAB R 2015a.