Abstract
In order to realize the following two goals including high electromechanical coupling coefficient (K2) and zero temperature coefficient of frequency (TCF) in a surface acoustic wave (SAW) device, the propagation characteristics of shear-horizontal type (SH-type) boundary waves in the Si/SiO2/Al/LiTaO3 “sandwich” structure are investigated by the three dimensional (3D) finite element method (FEM). The influences of layer SiO2 with different thickness (h) on the SH-type boundary waves characteristics, including the phase velocity (vp), reflection coefficient (kp), K2 and TCF, are theoretically analyzed. The results present that the SH-type boundary wave has a maximum K2 of 4.45% at h/λ=0.62 and has a zero TCF by adjusting h/λ to 0.69. Owing to the acoustic energy distribution approaching to the SiO2/LiTaO3 boundary, the size of Love wave based devices can be reduced to a few wavelength thickness of Si and 36°YX- LiTaO3 crystals, and which also give an opportunity to be integrated onto one chip with subsequent electronic circuits.
Highlights
Love wave based devices have attracted increasing attention in biochemical sensor,1,2 due to the high sensitivity3 with a mass sensitivity on value of 60 pg cm−2and pure shear polarization
Love wave is a type of shear horizontal surface acoustic wave (SH-SAW)
The admittance can be determined from the complete charge distribution on the electrodes, which characterizes the electrical behavior of the SAW device
Summary
Love wave based devices have attracted increasing attention in biochemical sensor, due to the high sensitivity with a mass sensitivity on value of 60 pg cm−2and pure shear polarization. Love wave based devices were made in 42.75○YX (ST-cut) quartz which provides a high sensitivity and good temperature stability.. Scitation.org/journal/adv angle or the propagation direction of Si and a piezoelectric material on Si/piezoelectric, such as Si/LiNbO3 and Si/LiTaO3 They pointed that these boundary waves in Si/piezoelectric may not be suitable enough for practical device applications, they proposed to insert an additional SiO2 layer between in Si and LiNbO3 substrates. Their results showed that this structure has a large K2 and a zero TCF with SiO2 thickness of 0.8λ. The mode shapes have been discussed in a sandwich structure with a special SiO2 thickness showing a zero TCF
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