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In this paper, we present the analytical study of thin film bulk acoustic wave resonators (FBARs) using ZnO and AlN films with a c-axis tilt angle (off-normal) from 0° to 180°. The tilted c-axis orientation induces normal plane and in-plane polarizations, which leads to the coexistence of the longitudinal mode and shear mode in the resonator. The equation for predicting electric impedance of FBARs was derived from the basic piezoelectric constitutive equations. Material properties including elastic, dielectric, and piezoelectric coefficients, bulk wave properties including acoustic velocity and electromechanical coupling coefficient, and impedance of FBARs were calculated and showed strong dependence on the tilt angle. Interestingly, it was found that for ZnO FBARs, pure thickness longitudinal modes occur at 0° and 65.4°, and pure thickness shear modes occur at 43° and 90°. For AlN FBARs, pure longitudinal modes occur at 0° and 67.1°, and pure shear modes occur at 46.1° and 90° for AlN. In other words, pure thickness longitudinal and shear modes exist in ZnO and AlN FBARs at specific tilted polarization angles. In addition, two peaks of shear mode electromechanical coefficient are found at 33.3° and 90° for ZnO, and 34.5° and 90° for AlN. Therefore, ZnO and AlN films with specific tilt angles may provide options in the design and fabrication of FBARs, considering their strong shear resonance with high electromechanical coefficients. The use of dual-mode FBARs for mass sensors is also analyzed; the calculated large resonant frequency shift caused by mass loading shows that they have good prospects for use in sensor applications with high sensitivity. The simulation results agreed well with the reported experiment results, and can be used for design and application of FBARs. [ABSTRACT FROM AUTHOR]

Electromechanical resonators have been widely used in signal processing and frequency control applications. It has been found that the resonant frequency of most resonator devices is highly temperature dependent, as temperature variation leads to materials properties change as well as resonator dimension change, which result in the undesirable shift of the resonance frequency. In this paper, we present a new frequency tuning method in which direct current (DC) bias field is used to control the resonance frequency of the piezoelectric resonator that is subjected to ambient temperature variations. It has been found that, depending on the polarity, the application of a DC bias field can reduce or increase the resonance frequency of the resonator. The experimental results demonstrate that the DC bias field tuning can achieve fairly good temperature compensation within a certain temperature range, and that the mechanical Q factor of the resonator is quite stable under different DC bias fields. [ABSTRACT FROM AUTHOR]

The brake system plays a key role in the safe operation of an automobile. As an important development direction of brake systems, electromechanical braking devices have attracted great interest because of their many advantages. Braking dynamics based on a twowheel vehicle model are analyzed in this paper. Then, an electromechanical brake device is designed and a simulation model of a vehicle ABS based on the electromechanical brake device is established. A sliding mode control system is designed to regulate the anti-lock braking system. The control algorithm is verified using a variety of operating conditions in vehicle dynamics simulation software. The simulation results show that the control method proposed in this paper can improve the braking effect. [ABSTRACT FROM AUTHOR]

It has been recognized that the control of crystalline orientation and thickness of Pb(Zr0.52Ti0.48)O3 (PZT) thin-films is very critical in the fabrication of piezoelectric thin-film devices with desirable dielectric and electromechanical properties. Here, we present our recent studies on the fabrication of PZT films with (001), (111), and random crystalline orientations onto platinized silicon substrates and the crystalline orientation dependence of the nanomechanical properties. A 1.0-μm PZT film with a strong (100) orientation is deposited by a 2–methoxyethanol- (2–MOE)-based sol–gel precursor solution, while random orientation is obtained by acetic acid-based sol–gel precursor. Rapid thermal annealing of 2–MOE sol-gel-based PZT films leads to strong (111) orientation. All PZT films show similar hysteresis behavior and large remnant polarizations; however, the nanomechanical test using AFM and nanoindentation indicates distinct values of Young’s modulus for PZT films with different orientations. [ABSTRACT FROM AUTHOR]