Abstract
A high-overtone bulk acoustic resonator (HBAR) consisting of a piezoelectric film with two electrodes on a substrate exhibits a high quality factor (Q) and multi-mode resonance spectrum. By analyzing the influences of each layer’s material and structure (thickness) parameters on the effective electromechanical coupling coefficient (Keff2), the resonance spectrum characteristics of Keff2 have been investigated systematically, and the optimal design of HBAR has been provided. Besides, a device, corresponding to one of the theoretical cases studied, is fabricated and evaluated. The experimental results are basically consistent with the theoretical results. Finally, the effects of Keff2 on the function of the crystal oscillators constructed with HBARs are proposed. The crystal oscillators can operate in more modes and have a larger frequency hopping bandwidth by using the HBARs with a larger Keff2·Q.
Highlights
Since the substrate thickness is much larger than the acoustic wavelength, the high-overtone bulk acoustic resonator (HBAR) will operate at a number of resonance frequencies; namely, HBAR has multi-frequency resonance characteristics, and it can be used as a multiple-frequency microwave source [1] and an agile-frequency synthesizer in electronic warfare
This paper presents a study on the resonance spectrum characteristics of Keff 2 changing with several common substrates, electrodes piezoelectric films as well as their thickness
The structure of Au/ZnO/Au/Sapphire with the appropriate thickness thickness of the substrate, piezoelectric film and electrode should be selected, as this can make the of the substrate, piezoelectric film and electrode should be selected, as this can make the crystal crystal oscillators obtain a larger frequency stability and frequency hopping bandwidth due to its oscillators2 obtain a larger frequency stability and frequency hopping bandwidth due to its larger larger Keff ·QM value
Summary
Zhang et al [8,9,10,11,12] conducted more in-depth research on the effects of the electrode and substrate materials as well as their thickness on the resonance spectrum distribution and the corresponding Keff 2 These above studies have mainly focused on Keff 2 -frequency distribution of Micromachines 2016, 7, 159; doi:10.3390/mi7090159 www.mdpi.com/journal/micromachines [14], shown, where ZtT = jZTtan(αT/2), ZtP = jZPtan(αP/2), ZtB = jZBtan(αB/2) and ZtS =. This paper presents a study on the resonance spectrum characteristics of Keff 2 changing with several common substrates, electrodes piezoelectric films as well as their thickness. A set of guidelines for the optimal selection of the HBAR’s parameters are provided
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