scholarly journals Anchor Loss Reduction of Lamb Wave Resonator by Pillar-Based Phononic Crystal

Micromachines ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 62
Author(s):  
Yinjie Tong ◽  
Tao Han
Keyword(s):  
Lamb Wave ◽  
High Frequency ◽  
Transmission Loss ◽  
Mechanical Energy ◽  
Phononic Crystal ◽  
Center Frequency ◽  
Electromechanical Coupling Coefficient ◽  
Wave Resonator ◽  
Energy Leakage ◽  
Anchor Loss

Energy leakage via anchors in substrate plates impairs the quality factor (Q) in microelectromechanical system (MEMS) resonators. Most phononic crystals (PnCs) require complicated fabrication conditions and have difficulty generating a narrow bandgap at high frequency. This paper demonstrates a pillar-based PnC slab with broad bandgaps in the ultra high frequency (UHF) range. Due to Bragg interference and local resonances, the proposed PnC structure creates notably wide bandgaps and shows great advantages in the high frequency, large electromechanical coupling coefficient (k2) thin film aluminum nitride (AlN) lamb wave resonator (LWR). The dispersion relations and the transmission loss of the PnC structure are presented. To optimize the bandgap, the influence of the material mechanical properties, lattice type, pillar height and pillar radius are explored. These parameters are also available to adjust the center frequency of the bandgap to meet the desirable operating frequency. Resonators with uniform beam anchors and PnC slab anchors are characterized. The results illustrate that the Q of the resonator improves from 1551 to 2384, and the mechanical energy leakage via the anchors is significantly decreased using the proposed PnC slab anchors. Moreover, employment of the PNC slab anchors has little influence on resonant frequency and induces no spurious modes. Pillar-based PnCs are promising in suppressing the anchor loss and further improving the Q of the resonators.

Surface acoustic wave resonator from thick MOVPE-grown layers of GaN(0001) on sapphire

2002 ◽  
Vol 743 ◽  
Author(s):  
Sverre V. Pettersen ◽  
Thomas Tybell ◽  
Arne Rønnekleiv ◽  
Stig Rooth ◽  
Veit Schwegler ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Electromechanical Coupling ◽  
Film Surface ◽  
Center Frequency ◽  
Electromechanical Coupling Coefficient ◽  
Nitride Film ◽  
Wave Resonator ◽  
Lift Off ◽  
Definition Of

ABSTRACTWe report on fabrication and measurement of a surface acoustic wave resonator prepared on ∼10m thick GaN(0001) films. The films were grown by metal-organic vapor phase epitaxy on a c-plane sapphire substrate. The surface morphology of the films were examined with scanning electron and atomic force microscopy. A metallic bilayer of Al/Ti was subsequently evaporated on the nitride film surface. Definition of the resonator interdigital transducers, designed for a wavelength of λ=7.76m, was accomplished with standard UV lithography and lift-off. S-parameter measurements showed a resonator center frequency f0=495MHz at room temperature, corresponding to a surface acoustic wave velocity of 3844m/s. The insertion loss at center frequency was measured at 8.2dB, and the loaded Q-factor was estimated at 2200. Finally, measurements of the resonator center frequency for temperatures in the range 25–155°C showed a temperature coefficient of -18ppm/°C. The intrinsic GaN SAW velocity and electromechanical coupling coefficient were estimated at νSAW=383 1m/s and K2=1.8±0.4·10−3.

A Piezoelectric on Substrate Phononic Band Gap High-Q Micromechanical Resonator

2009 ◽  
Author(s):  
Saeed Mohammadi ◽  
Ali Asghar Eftekhar ◽  
Ali Adibi
Keyword(s):  
High Frequency ◽  
High Efficiency ◽  
Mechanical Energy ◽  
Phononic Crystal ◽  
Building Blocks ◽  
Piezoelectric Medium ◽  
Resonant Structure ◽  
High Quality ◽  
High Q ◽  
Sensing Applications

Micromechanically-fabricated phononic crystal (PnC) structures with phononic band gaps (PnBGs) are gaining a growing attention due to their high efficiency in controlling and confining mechanical energy in micro and nano-scale structures. Preliminary PnC devices such as waveguides and resonators based on the complete PnBG of the micro-machined PnC structures have shown a great potential to improve the characteristics of the conventional micro-mechanical (MM) devices [1–5]. Especially high-frequency, high-quality factor (Q) MM resonators are of great interest as they are main building blocks for realizing compact and complex devices such as filters, multiplexers and de-multiplexers for wireless communications and sensing applications. Therefore, development of high-Q, high-frequency PnC-based MM resonators is an important step towards realizing functional PnC-based devices with potentially better performance compared to their conventional counterparts. In this paper, we report, for the first time, a PnC slab piezoelectric-on-substrate MM resonator operating at VHF frequencies which supports high Q modes. The excitation of the resonant modes in these structures is done directly on the resonant structure (in contrast to the resonant tunneling excitation method reported earlier [5]) and therefore, no coupling from outside of the resonant structure is required. In such a structure, enough number of PnC periods can be placed around the resonant region to provide enough isolation from the surroundings; consequently the loss of the mechanical energy will be limited to material and friction losses only. We report a Fabry-Perot-type PnC slab resonator with an electrode and a piezoelectric medium directly fabricated on top of a resonant structure and show that high quality factors can be obtained in such a compact resonator. As a result, a flexural and a longitudinal mode are excited. Q’s of more than 3600 and 10,000 are obtained for the two modes with motional resistances of 1200 Ω and 5000 Ω. Such piezoelectrically excited high-Q resonators operating at such high frequencies evidence the possibility of suppressing support loss (an important source of loss) in MM resonators through the use of the especial structure of a PnC. Such PnC resonators can have a great impact on the current state-of-the-art MM devices used in wireless communication and sensing systems.

scholarly journals Fabrication and Characterization of High-Frequency Ultrasound Transducers Based on Lead-Free BNT-BT Tape-Casting Thick Film

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3166 ◽  
Author(s):  
Junshan Zhang ◽  
Wei Ren ◽  
Yantao Liu ◽  
Xiaoqing Wu ◽  
Chunlong Fei ◽  
...  
Keyword(s):  
Thick Film ◽  
High Frequency ◽  
Electromechanical Coupling ◽  
Ultrasonic Transducer ◽  
Tape Casting ◽  
Lead Free ◽  
Center Frequency ◽  
Electromechanical Coupling Coefficient ◽  
High Frequency Ultrasound ◽  
Casting Method

A lead-free 0.94(Na0.5Bi0.5) TiO3-0.06 BaTiO3 (BNT-BT) thick film, with a thickness of 60 μm, has been fabricated using a tape-casting method. The longitudinal piezoelectric constant, clamped dielectric permittivity constant, remnant polarization and coercive field of the BNT-BT thick film were measured to be 150 pC/N, 1928, 13.6 μC/cm2, and 33.6 kV/cm, respectively. The electromechanical coupling coefficient kt was calculated to be 0.55 according to the measured electrical impedance spectrum. A high-frequency plane ultrasound transducer was successfully fabricated using a BNT-BT thick film. The performance of the transducer was characterized and evaluated by the pulse-echo testing and wire phantom imaging operations. The BNT-BT thick film transducer exhibits a center frequency of 34 MHz, a −6 dB bandwidth of 26%, an axial resolution of 77 μm and a lateral resolution of 484 μm. The results suggest that lead-free BNT-BT thick film fabricated by tape-casting method is a promising lead-free candidate for high-frequency ultrasonic transducer applications.

scholarly journals Fabrication of AlGaN High Frequency Bulk Acoustic Resonator by Reactive RF Magnetron Co-sputtering System

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7377
Author(s):  
Yu-Chen Chang ◽  
Ying-Chung Chen ◽  
Chien-Chuan Cheng
Keyword(s):  
Aluminum Gallium Nitride ◽  
High Frequency ◽  
Electromechanical Coupling ◽  
Acoustic Resonator ◽  
Bragg Reflector ◽  
Center Frequency ◽  
Electromechanical Coupling Coefficient ◽  
Axis Orientation ◽  
Sputtering Power ◽  
Sputtering System

In this study, aluminum gallium nitride (AlGaN) thin films are used as the piezoelectric layers to fabricate solidly mounted resonators (SMR) for high frequency acoustic wave devices. AlGaN film is deposited on a Bragg reflector, composed of three pairs of Mo and SiO2 films, through a reactive radio frequency (RF) magnetron co-sputtering system at room temperature. The optimized deposition parameters of AlGaN film have a sputtering power of 175 W for Al target, sputtering power of 25 W for GaN target, N2 flow ratio (N2/Ar + N2) of 60%, and sputtering pressure of 10 mTorr. The obtained AlGaN film has a smooth surface, uniform crystal grains, and strong c-axis orientation. The contents of Al and Ga in the AlGaN film, analyzed by energy dispersive X-ray spectroscopy (EDS) are 81% and 19%, respectively. Finally, the frequency response S11 of the obtained SMR device shows that the center frequency is 3.60 GHz, the return loss is about −8.62 dB, the electromechanical coupling coefficient (kt2) is 2.33%, the quality factor (Q) value is 96.93 and the figure of merit (FoM) value is 2.26.

GHz spurious mode free AlN lamb wave resonator with high figure of merit using one dimensional phononic crystal tethers

2016 ◽  
Vol 109 (1) ◽  
pp. 013506 ◽  
Author(s):  
Guoqiang Wu ◽  
Yao Zhu ◽  
Srinivas Merugu ◽  
Nan Wang ◽  
Chengliang Sun ◽  
...  
Keyword(s):  
Lamb Wave ◽  
Figure Of Merit ◽  
Phononic Crystal ◽  
One Dimensional ◽  
Wave Resonator ◽  
Spurious Mode ◽  
High Figure

Design and Experiment of Capacitive Micromachined Ultrasonic Transducer Array for High-Frequency Underwater Imaging

2020 ◽  
Vol 13 ◽  
Author(s):  
Yuanyu Yu ◽  
Jiujiang Wang ◽  
Xin Liu ◽  
Sio Hang Pun ◽  
Weibao Qiu ◽  
...  
Keyword(s):  
Ultrasound Imaging ◽  
High Frequency ◽  
Ultrasonic Transducer ◽  
Center Frequency ◽  
Design Parameters ◽  
Underwater Imaging ◽  
Release Process ◽  
Steel Wires ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
Frequency Ultrasound

Background:: Ultrasound is widely used in the applications of underwater imaging. Capacitive micromachined ultrasonic transducer (CMUT) is a promising candidate to the traditional piezoelectric ultrasonic transducer. In underwater ultrasound imaging, better resolutions can be achieved with a higher frequency ultrasound. Therefore, a CMUT array for high-frequency ultrasound imaging is proposed in this work. Methods:: Analytical methods are used to calculate the center frequency in water and the pull-in voltage for determining the operating point of CMUT. Finite element method model was developed to finalize the design parameters. The CMUT array was fabricated with a five-mask sacrificial release process. Results:: The CMUT array owned an immersed center frequency of 2.6 MHz with a 6 dB fractional bandwidth of 123 %. The pull-in voltage of the CMUT array was 85 V. An underwater imaging experiment was carried out with the target of three steel wires. Conclusion:: In this study, we have developed CMUT for high-frequency underwater imaging. The experiment showed that the CMUT can detect the steel wires with the diameter of 100 μm and the axial resolution was 0.582 mm, which is close to one wavelength of ultrasound in 2.6 MHz.

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