Abstract
The propagation of the first symmetric Lamb mode S0 along ZnO/a-SiC thin composite plates was modeled and analysed aimed at the design of a sensor able to detect the changes of the environmental parameters, such as added mass in vacuum and the liquid viscosity changes in a viscous liquid medium. The Lamb mode propagation was modeled by numerically solving the system of coupled electro-mechanical field equations in the two media. The S0 acoustic field profile was calculated aimed at finding the proper plate thickness suitable for the propagation of longitudinally polarized modes. The phase velocity and electroacoustic coupling efficiency dispersion curves of the S0 mode were calculated aimed at the design of enhanced coupling efficiency devices. The gravimetric sensitivity in vacuum, and the attenuation that the S0 mode soffers when contacting a liquid viscous Newtonian environment were finally calculated for different ZnO layer thicknesses. Recently obtained results on the sputtering deposition of the a-SiC and ZnO thin and thick layers on Si substrates are also reported.
Highlights
Lamb waves are acoustic modes that propagate along finite thickness plats with thicknesses smaller than the acoustic wavelength λ
We theoretically investigate the design of an a-SiC/ZnO Lamb wave sensor, which is suitable for the fabrication of a sensor able to operate in liquid environment
The propagation characteristics of the fundamental symmetric Lamb mode S0 along thin composite plates based on amorphous SiC and piezoelectric c-ZnO layers were studied, aimed at the design of a high frequency electroacoustic device suitable to work in liquid environment
Summary
Lamb waves are acoustic modes that propagate along finite thickness plats with thicknesses smaller than the acoustic wavelength λ. The first symmetric Lamb mode S0 is polarized parallel to the wave propagation direction just for a limited plate thicknesses range. The longitudinal polarization makes the S0 mode devices suitable for liquid environment applications. ZnO/a-SiC-based thin plates for Lamb wave devices implementation require the growth of a thin a-SiC and ZnO layers onto a silicon substrate, and the silicon micromachining to obtain a suspended thin membrane. Piezoelectric wurtzite ZnO thin film technology has been widely used since many years for the fabrication of acoustic wave (AW) devices onto non piezoelectric substrates. We theoretically investigate the design of an a-SiC/ZnO Lamb wave sensor, which is suitable for the fabrication of a sensor able to operate in liquid environment. The aim of the present theoretical calculations is to investigate the influence of the ZnO layer thickness on the performances of a Lamb wave device for biosensor applications.
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