Showing papers by "Roozbeh Tabrizian published in 2016"

High-Q energy trapping of temperature-stable shear waves with Lamé cross-sectional polarization in a single crystal silicon waveguide

Abstract: A multi-port electrostatically driven silicon acoustic cavity is implemented that efficiently traps the energy of a temperature-stable eigen-mode with Lame cross-sectional polarization. Dispersive behavior of propagating and evanescent guided waves in a ⟨100⟩-aligned single crystal silicon waveguide is used to engineer the acoustic energy distribution of a specific shear eigen-mode that is well known for its low temperature sensitivity when implemented in doped single crystal silicon. Such an acoustic energy trapping in the central region of the acoustic cavity geometry and far from substrate obviates the need for narrow tethers that are conventionally used for non-destructive and high quality factor (Q) energy suspension in MEMS resonators; therefore, the acoustically engineered waveguide can simultaneously serve as in-situ self-oven by passing large uniformly distributed DC currents through its body and without any concern about perturbing the mode shape or deforming narrow supports. Such a stable therm...

Bilayer nano-waveguide resonators for sensing applications

Abstract: This paper presents an acoustically engineered nano-waveguide resonator implemented in an aluminum nitride-on-silicon bilayer with an overall thickness of less than 200nm. Acoustic engineering using dispersion characteristics of laterally propagating waves with cross-sectional flexural polarization has been used to realize efficient energy trapping without the need for narrow suspending supports, thus improving device power handling. Having a large aspect ratio, the bilayer nano-waveguide resonator experiences an amplified thermally induced axial stress, which results in a very high temperature coefficient of its resonance frequency. Such characteristics along with the minuscule volume and large peripheral acoustic energy density make the device an exceptional candidate for sensing applications where an increased thermal responsivity and large interaction cross-section are desirable. A prototype device operating at ∼870kHz frequency with a Q of ∼140 — measured in air — shows a vibration amplitude of 100nm at 3V and a linear TCF of ∼ −710 ppm / °C when actuated piezoelectrically with 500 mv at resonance.