Abstract
This study focuses on the mechanical response of silicon on porous silicon bilayer cantilevers ended with a seismic mass. The porous silicon is intended to provide an alternative to decrease the cantilever stiffness for low-frequency MEMS applications. The first eigenfrequency of the cantilever is obtained using static deflection obtained under classical Euler-Bernoulli assumptions and Rayleigh method. In order to estimate the errors due to small-strain approximation and Euler-Bernoulli theory, the analytical results were validated through 3D finite element simulations for different cantilever geometries and porosities. Both bulk silicon and silicon on porous silicon bilayer cantilevers ended with a seismic mass were fabricated and we measured the first eigenfrequency (f0) and quality factor (Q) by using a laser Doppler vibrometer. In agreement with the theoretical predictions we found that, when compared to bulk silicon cantilevers, the first eigenfrequency of a bilayer cantilever containing 6% porous silicon (at 50% porosity) on 94% bulk silicon is lowered by 5%, from (5447 ± 120) Hz to ≈ 5198 Hz. This decrease is also accompanied by a reduction of the quality factor by two.
Highlights
The concept of energy harvesting gained new relevance since the recent development of ultra low-power embedded electronic devices
This study focuses on the mechanical response of silicon on porous silicon bilayer cantilevers ended with a seismic mass
Both bulk silicon and silicon on porous silicon bilayer cantilevers ended with a seismic mass were fabricated and we measured the first eigenfrequency (f0) and quality factor (Q) by using a laser Doppler vibrometer
Summary
The concept of energy harvesting gained new relevance since the recent development of ultra low-power embedded electronic devices. Energy harvesting from ambient vibrations enables new exciting opportunities for low power nano-. A first challenge is the design of miniaturized resonators able to reach such low frequencies, and this is difficult since eigenfrequencies tend to increase with shrinking dimensions and mass. In order to use electro-active materials in thin films, a second challenge in device miniaturization is to preserve the good intrinsic coupling between these materials. The maximum power one can expect to retrieve depends on this coupling and on the quality factor of the harvesting device
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