Showing papers on "Interdigital transducer published in 2019"

Comparative Study of Acoustic Wave Devices Using Thin Piezoelectric Plates in the 3–5-GHz Range

Abstract: This paper investigates the applicability of acoustic wave devices using an interdigital transducer placed on a thin piezoelectric crystal plate to the 3–5-GHz range, where significant performance degradation was expected in surface acoustic wave (SAW) devices. Three types of the SAW-like devices were fabricated by using a KrF stepper/scanner, and their performances are compared from various aspects: 1) a 3.5-GHz resonator using a rotated $Y$ -cut LiTaO3 plate attached on a Si substrate; 2) a 5-GHz resonator using a $X$ -cut LiNbO3 plate on a Si substrate; and 3) a 5.4-GHz $A_{1}$ Lamb mode resonator on a free-standing $Z$ -cut LiNbO3 plate. It is revealed that these devices offer excellent performances even in the 3–5-GHz range.

Microwave-to-optical conversion using lithium niobate thin-film acoustic resonators

Abstract: Acoustic or mechanical resonators have emerged as a promising means to mediate efficient microwave-to-optical conversion. Here, we demonstrate conversion of microwaves up to 4.5 GHz in frequency to 1500 nm wavelength light using optomechanical interactions on suspended thin-film lithium niobate. Our method uses an interdigital transducer that drives a freestanding 100 μm-long thin-film acoustic resonator to modulate light traveling in a Mach–Zehnder interferometer or racetrack cavity. The strong microwave-to-acoustic coupling offered by the transducer in conjunction with the strong photoelastic, piezoelectric, and electro-optic effects of lithium niobate allows us to achieve a half-wave voltage of Vπ=4.6 V and Vπ=0.77 V for the Mach–Zehnder interferometer and racetrack resonator, respectively. The acousto-optic racetrack cavity exhibits an optomechanical single-photon coupling strength of 1.1 kHz. To highlight the versatility of our system, we also demonstrate a microwave photonic link with unitary gain, which refers to a 0 dB microwave power transmission over an optical channel. Our integrated nanophotonic platform, which leverages the compelling properties of lithium niobate, could help enable efficient conversion between microwave and optical fields.

Microwave-to-optical conversion using lithium niobate thin-film acoustic resonators

Abstract: We demonstrate conversion of up to 4.5 GHz-frequency microwaves to 1500 nm-wavelength light using optomechanical interactions on suspended thin-film lithium niobate. Our method utilizes an interdigital transducer that drives a free-standing 100 $\mu$m-long thin-film acoustic resonator to modulate light travelling in a Mach-Zehnder interferometer or racetrack cavity. Owing to the strong microwave-to-acoustic coupling offered by the transducer in conjunction with the strong photoelastic, piezoelectric, and electro-optic effects of lithium niobate, we achieve a half-wave voltage of $V_\pi$ = 4.6 V and $V_\pi$ = 0.77 V for the Mach-Zehnder interferometer and racetrack resonator, respectively. The acousto-optic racetrack cavity exhibits an optomechancial single-photon coupling strength of 1.1 kHz. Our integrated nanophotonic platform coherently leverages the compelling properties of lithium niobate to achieve microwave-to-optical transduction. To highlight the versatility of our system, we also demonstrate a lossless microwave photonic link, which refers to a 0 dB microwave power transmission over an optical channel.

Traveling surface acoustic wave (TSAW) microfluidic fluorescence activated cell sorter (μFACS)

Abstract: We report a microfluidic fluorescence activated cell-sorting (μFACS) device that employs traveling surface acoustic waves (TSAW) to sort cells at rates comparable to conventional jet-in-air FACS machines, with high purity and viability. The device combines inertial flow focusing and sheath flow to align and evenly space cells, improving the sorting accuracy and screening rate. We sort with an interdigital transducer (IDT) whose tapered geometry allows precise positioning of the TSAW for optimal cell sorting. We sort three different cell lines at several kHz, at cell velocities exceeding one meter per second, while maintaining both sorting purity and cell viability at around 90% simultaneously.

Surface acoustic wave-based micromixing enhancement using a single interdigital transducer

Abstract: The realization of efficient mixing of samples inside a microfluidic channel is essential for performing numerous biological assays in miniaturized total analysis systems. The low Reynolds number flows at the microscale create laminar streams inside the microchannel, limiting flow mixing to a molecular diffusion level. In this paper, we propose a simple and efficient acoustofluidic mixing technique inside a single-layered polydimethylsiloxane (PDMS) microfluidic channel. The proposed surface acoustic wave (SAW)-based system composed of a straight interdigitated transducer (IDT) is positioned beneath the PDMS microchannel. Fluorescein dye dissolved in deionized water (sample fluid) and deionized water (sheath fluid) was introduced through the first and second inlets of the PDMS microchannel, respectively. Their flow rates were controlled such that the sample fluid with fluorescein dye was hydrodynamically focused close to the bottom of the microchannel by the sheath fluid. High-frequency (140 MHz) SAWs, generated from the IDT placed right beneath the first outlet, mixed the two fluids under the influence of strong acoustic streaming flows. The mixed samples were then collected at the two outlet ports for further analysis of the mixing efficiency. The developed acoustofluidic mixing device required an input voltage of 12 Vpp at a total flow rate of 50 μl/min to realize complete mixing. At a similar applied voltage, the throughput of the proposed device could be further increased to 200 μl/min with a mixing efficiency of >90%.

Cavity-free vacuum-Rabi splitting in circuit quantum acoustodynamics

Abstract: Artificial atoms coupled to surface acoustic waves (SAWs) have played a crucial role in the recent development of circuit quantum acoustodynamics. In this paper, we have investigated the interaction of an artificial atom and SAWs beyond the weak-coupling regime, focusing on the role of the interdigital transducer (IDT) that enables the coupling. We find a parameter regime in which the IDT acts as a cavity for the atom, rather than an antenna. In other words, the atom forms its own cavity. Similar to an atom coupled to an explicit cavity, this regime is characterized by vacuum-Rabi splitting, as the atom hybridizes with the phononic vacuum inside the IDT. This hybridization is possible because of the interdigitated coupling, which has a large spatial extension, and the slow propagation speed of SAWs. We work out a criterion for entering this regime from a model based on standard circuit-quantization techniques, taking only material parameters as inputs. Most notably, we find this regime hard to avoid for an atom on top of a strong piezoelectric material, such as lithium niobate (LiNbO3). The SAW-coupled atom on top of LiNbO3 can thus be regarded as an atom-cavity-bath system. On weaker piezoelectric materials, the number of IDT electrodes needs to be large in order to reach this regime.

Contactless, programmable acoustofluidic manipulation of objects on water.

Abstract: Contact-free manipulation of small objects (e.g., cells, tissues, and droplets) using acoustic waves eliminates physical contact with structures and undesired surface adsorption. Pioneering acoustic-based, contact-free manipulation techniques (e.g., acoustic levitation) enable programmable manipulation but are limited by evaporation, bulky transducers, and inefficient acoustic coupling in air. Herein, we report an acoustofluidic mechanism for the contactless manipulation of small objects on water. A hollow-square-shaped interdigital transducer (IDT) is fabricated on lithium niobate (LiNbO3), immersed in water and used as a sound source to generate acoustic waves and as a micropump to pump fluid in the ±x and ±y orthogonal directions. As a result, objects which float adjacent to the excited IDT can be pushed unidirectionally (horizontally) in ±x and ±y following the directed acoustic wave propagation. A fluidic processor was developed by patterning IDT units in a 6-by-6 array. We demonstrate contactless, programmable manipulation on water of oil droplets and zebrafish larvae. This acoustofluidic-based manipulation opens avenues for the contactless, programmable processing of materials and small biosamples.

Transverse Spurious Mode Compensation for AlN Lamb Wave Resonators

Abstract: Lamb wave modes with type I dispersion characteristics exhibit strong affinity toward multi transverse modes behavior above resonance frequency (f r ) in the AlN Lamb wave resonators (LWRs), especially the high-transduction-efficiency modes: S 0 and S 1 mode. For conventional interdigital transducer (IDT) design, the IDT aperture and IDT gap are the two main factors impacting the transverse mode placements and strengths, according to the wave vector analysis and finite element method (FEM) simulation. Moreover, the convex slowness curve of the Lamb wave modes propagating in AlN platelets allows the waveguiding and weak lateral leakage into busbars by the high-velocity IDT gap region. Apodization, the standard technique to suppress the transverse modes for IDT-excited resonators, suffers from drawbacks, such as additional loss and reduction of the effective coupling coefficient (k eff 2 ). Type I Lamb wave modes in AlN show positive slope in the dispersion branch so that a border region of lower Eigen-resonance frequency is required to form piston mode structure for transverse spurious mode suppression and lateral leakage reduction. Based on dispersion calculations and 2.5D FEM simulations, we demonstrate that by designing the low-velocity border region, such as simply changing the IDT layout, the guiding can be improved and a piston mode can be obtained for the type I Lamb wave modes.

Development of chipless and wireless underground temperature sensor system based on magnetic antennas and SAW sensor

Abstract: A chipless and wireless underground sensor system was developed based on two magnetic coil antennas with magnetic cores and a surface acoustic wave (SAW) resonator sensor to monitor temperature variations around buried utilities from the ground. A ∼250 MHz alternating current from the magnetic antenna generates a SAW along the piezoelectric substrate, and the returned SAW energy owing to the reflection bars on the sensor is reconverted to magnetic flux by the sensor’s interdigital transducer (IDT) and subsequently transmitted to a reader via magnetic antenna. By observing changes in the center frequency of the SAW sensor with temperature, we were able to monitor the underground temperature variations in real time. The developed magnetic coil antenna has a large diameter Ni0.8Fe0.2 core wound by Cu coil, and a convex shape at the core end to converge the magnetic flux and enhance the readout distance. Two types of temperature sensors, a one-port SAW resonator and two-port SAW reflective delay line, were fabricated on a 128° YX LiNbO3 and their characteristics were compared in terms of soil temperature. SAW generation by magnetic antenna followed by SAW propagation along the piezoelectric substrate were each confirmed by the AC voltages derived at the output IDT on the SAW sensor, and the amplitude of the SAW was greatly dependent on the current applied to the coil. In soil testing, long readout distance between the reader and underground SAW sensor was observed. The temperature sensors provided stable performance in terms of underground temperature changes, soil type, and soil compactness at that readout distance. The resultant sensitivity and linearity for the SAW resonator temperature sensor was 0.3 MHz/oC and 0.96, respectively. COMSOL and coupling of Mode (COM) modeling were also performed to find the optimal sensor system parameters and predict the results in advance.

Graphene-Based Fully Transparent Thin Film Surface Acoustic Wave Devices for Sensing and Lab-on-Chip Applications

Abstract: This paper explores to use graphene as transparent interdigital transducer (IDT) electrode for a fully transparent surface acoustic wave (SAW) device due to its extraordinary electrical, physical and mechanical properties. The number of graphene atomic layers was firstly optimized for its best performance as the SAW electrode, and a 4-layered graphene IDT electrode, with aluminum doped zinc oxide, AZO, as the bus bar and wire bonding pad, was selected to fabricate fully transparent ZnO/glass SAW devices. The SAW resonators exhibited obvious resonant response at different wavelengths, and resonance signals with amplitude up to 20 dB were obtained with the transparency above 80%. The graphene-based transparent SAW sensor has been used for differ-ent sensing applications. Temperature sensing tests showed that the frequencies increase linearly with the increase of temperature, which has an opposite trend compared to that obtained from a conventional LiNbO3 SAW device. The humidity sensing and human breathing detection have been demonstrated, and discontinuous respiration measurement can be used to distinguish the human respiration at the normal state or the state after exercise. Strong acoustic streaming and particle concentration using the transparent SAW devices have been achieved, which are suitable for microfluidic and lab-on-chip applications.

Acoustophoretic Control of Microparticle Transport Using Dual-Wavelength Surface Acoustic Wave Devices.

Abstract: We present a numerical and experimental study of acoustophoretic manipulation in a microfluidic channel using dual-wavelength standing surface acoustic waves (SSAWs) to transport microparticles into different outlets. The SSAW fields were excited by interdigital transducers (IDTs) composed of two different pitches connected in parallel and series on a lithium niobate substrate such that it yielded spatially superimposed and separated dual-wavelength SSAWs, respectively. SSAWs of a singltablee target wavelength can be efficiently excited by giving an RF voltage of frequency determined by the ratio of the velocity of the SAW to the target IDT pitch (i.e., f = cSAW/p). However, the two-pitch IDTs with similar pitches excite, less efficiently, non-target SSAWs with the wavelength associated with the non-target pitch in addition to target SSAWs by giving the target single-frequency RF voltage. As a result, dual-wavelength SSAWs can be formed. Simulated results revealed variations of acoustic pressure fields induced by the dual-wavelength SSAWs and corresponding influences on the particle motion. The acoustic radiation force in the acoustic pressure field was calculated to pinpoint zero-force positions and simulate particle motion trajectories. Then, dual-wavelength SSAW acoustofluidic devices were fabricated in accordance with the simulation results to experimentally demonstrate switching of SSAW fields as a means of transporting particles. The effects of non-target SSAWs on pre-actuating particles were predicted and observed. The study provides the design considerations needed for the fabrication of acoustofluidic devices with IDT-excited multi-wavelength SSAWs for acoustophoresis of microparticles.

Interdigital transducers on a piezoelectric thin-film for signal compression

Abstract: A piezoelectric thin-film suspended above a carrier substrate. An input interdigital transducer (IDT) having first interdigitated electrodes is disposed at different locations along the horizontal axis and on the first side of the piezoelectric thin-film. Each opposing pair of the first interdigitated electrodes is to selectively transduce a particular frequency range of an input electrical signal that varies in frequency over time into an acoustic wave of a laterally vibrating mode based on a pitch between electrodes of the opposing pair. An output IDT that includes second interdigitated electrodes is disposed at different locations along the horizontal axis and on the second side of the piezoelectric thin-film. Each opposing pair of the second interdigitated electrodes is to convert the acoustic wave transduced by the respective opposing pair of the first interdigitated electrodes into a compressed pulse.

Analysis on scattering characteristics of Love-type wave due to surface irregularity in a piezoelectric structure

Abstract: Surface irregularity in piezoelectric sensors causes scattering of Love-type waves, which may lead to significant signal insertion loss. Also, as the reflected wave field in the piezoelectric sensor is increased due to surface irregularity, the input interdigital transducer (IDT) can be damaged. The present analysis confers the characteristics of Love-type waves scattered through surface irregularity in piezoelectric composite structures with different shaped surface irregularity, e.g., rectangular shaped, parabolic shaped, and triangular notch shaped. The expressions of phase and group velocities of scattered Love-type waves are derived for electrically open and short conditions. Also, expressions of mechanical displacement and electrical potential function due to incident and scattered Love-type waves are deduced for both electrical conditions. It is reported from the analysis that the increase in vertical irregularity parameter causes stronger reflected wave fields. Also, with the increase in piezoelectricity of the superficial layer, signal insertion loss and strength of reflected wave field diminish.

Acoustic Kerr nonlinearity of wave propagation in a planar nanoelectromechanical waveguide

Abstract: Nonlinearity is the key to introducing novel concepts in various technologies utilizing traveling waves. In contrast to the field of optics, where highly functional devices have been developed using optical Kerr nonlinearity, such a nonlinear effect in acoustic devices has yet to be fully exploited. Here, we show that most fundamental nonlinear phenomena of self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM) caused by the acoustic Kerr effect are quantitatively characterized using a newly developed platform consisting of a planar nanoelectromechanical waveguide (NEMW). Combining the cutting-edge technology of a high crystalline quality NEMW with a piezoelectric interdigital transducer (IDT), we efficiently excite an intense and long-lived traveling wave sufficiently to induce and characterize acoustic nonlinearity. The observed nonlinear phenomena are precisely described by the model using the nonlinear Schrodinger (NLS) equation, so that this architecture enables the nonlinear dynamics to be perfectly tailored. The flexible and integratable platform extends the ability to manipulate acoustic wave propagation on a chip, thus offering the potential to develop highly functional devices and study novel nonlinear acoustics.

Lamb-wave sparse-frequency interdigital-transducer-based scanning laser Doppler vibrometry for quantitative depth-wise visualization of defects in plates

Abstract: The Lamb-wave-based scanning laser Doppler vibrometry (SLDV) technique, which uses continuous excitation, is considered a promising method for visualizing defects in plate-like structures. To visualize defects, the technique commonly uses the A0 mode because of its sensitivity to thickness variations, i.e., the wave speed changes according to the thickness. However, for thick plates, the A0 mode is found to be less sensitive to thickness variations relative to thin structures. Thus, to address this issue, interdigital transducer (IDT)-based SLDV has recently been proposed to efficiently generate a symmetric mode for damage detection in thick plates. In this study, with the use of an IDT-based SLDV, we demonstrate that the detectability of shallow defects in a thick plate (6 mm) in the S0 mode is superior to that with the A0 mode. In addition, we show that by using just a single guided-wave mode, it is difficult to detect defects at different depths for a 6-mm-thick carbon steel plate. To improve the damage detection capability over the entire range of thickness variation of a thick carbon steel plate, we select three excitation frequencies (200, 450, and 600 kHz) based on the analysis of wavenumber sensitivity and the degree separation between modes (DSM). Subsequent to the fusion of the images corresponding to the three frequencies, we demonstrate that the defect detectability in a thick carbon steel plate using sparse-frequency IDT-based SLDV is improved over that with the use of the single guided-wave mode. Our findings can significantly contribute to advancements in the nondestructive testing of plates using SLDV.

Simulation of temperature compensated waveguiding layer acoustic wave devices

Abstract: Packageless structure which can reduce dimension has been a hot spot of research, while devices with temperature stability have received great attention. The temperature compensated waveguiding layer acoustic wave (WLAW) is a good candidate for devices with packageless structure and temperature stability. We propose an AlN/interdigital transducer (IDT)/ZnO/SiO2/Si multi-layered structure and investigate the propagation characteristics of the wave by simulation. The influence of the AlN thickness on the wave confinement is discussed, while the phase velocity, electromechanical coupling factor (K 2) and temperature coefficient of frequency (TCF) are provided as functions of the normalized ZnO and SiO2 thicknesses. The results show that a WLAW with nearly zero TCF can be obtained in the structure where the thickness of AlN is larger than 1.5 λ (λ stands for the wavelength of the acoustic wave), that of ZnO is between 0.2 λ and 0.3 λ, while the thickness of SiO2 is about three times that of ZnO. In this multi-layered structure, we can obtain temperature compensated WLAW devices with different frequencies and K 2. This work can provide instruction for experiments and is also useful for preparing devices with different velocities, K 2 and TCF based on this multi-layered structure.

Surface acoustic wave devices with graphene interdigitated transducers

Abstract: This paper reports the development of high performance surface acoustic wave (SAW) devices by using graphene as a virtually massless interdigital transducer (IDT) to mitigate mass-loading effects. Different layers of graphene electrodes were made and their influences on the SAW device performance were experimentally and theoretically evaluated. Results showed that 4-layer graphene with a value of sheet resistance less than 77.6 ? sq?1 and graphene IDTs of at least 80 pairs are needed to obtain the optimum performance of graphene IDT SAW devices. Furthermore, the optimal ratio of aperture/wavelength for the graphene IDT electrode was found to be 5. Graphene based SAW devices, with a resonance frequency of 154 MHz, transmission signal amplitude of 30 dB and K 2 of 3.78%, were fabricated and successfully demonstrated for applications in breathing monitoring.

Design of Ultra-Large-Coupling SH 0 Plate Wave Resonators on LiNbO 3 with Clean Spectrum

Abstract: This study lays a foundation for the design of the SH 0 Plate acoustic wave (PAW) resonator based on LiNbO 3 plate applicable to the ultra-wide-band filters and next-generation tunable filters. The coupling coefficient (k2) of SH 0 mode is optimized to as high as 55% by analyzing the propagation characteristics of Plate modes in LiNbO 3 membrane with different cut angle and normalized thicknesses. The SH 0 mode is demonstrated to be slowly dispersive and it features the superiority of interdigital transducer (IDT) - defining frequency over most other Plate modes. On device level, the transducer types, transducer materials and thicknesses are investigated and compared. In addition, both the out-of-band (plate modes mainly) and in-band spurious modes (longitudinal modes) are investigated and suppressed for the SH 0 PAW resonators.

Transversely-excited film bulk acoustic resonators for high power applications

Abstract: There is disclosed acoustic resonators and filter devices. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. A thickness of the interleaved fingers of the IDT is greater than or equal to 0.85 times a thickness of the piezoelectric plate.

Transversely excited film bulk acoustic resonator using rotated Y-X cut lithium niobate

Abstract: Acoustic resonator devices, filters, and methods are disclosed. An acoustic resonator includes a substrate and a lithium niobate (LN) plate having parallel front and back surfaces, the back surface attached to a surface of the substrate except for a portion of the LN plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the LN plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. A direction of acoustic energy flow of the primary acoustic mode is substantially orthogonal to the surfaces of the diaphragm. The Euler angles of the LN plate are 0°, β, 90°, where β is greater than or equal to −15° and less than 0°.

Surface acoustic wave pressure sensor and its matched antenna design

Abstract: Interdigital transducer and signal transmission in surface acoustic wave pressure sensor design is one of the difficulties in sensor design. The transmission antenna is an important design indicato...

Solidly-mounted transversely-excited film bulk acoustic resonator

Abstract: Resonator devices, filter devices, and methods of fabrication are disclosed. A resonator device includes a substrate and a single-crystal piezoelectric plate having parallel front and back surfaces. An acoustic Bragg reflector is sandwiched between a surface of the substrate and the back surface of the single-crystal piezoelectric plate. An interdigital transducer (IDT) is formed on the front surface. The IDT is configured to excite shear acoustic waves in the piezoelectric plate in response to a radio frequency signal applied to the IDT.

Analysis on Characteristics of ZnO Surface Acoustic Wave with and without Micro-Structures.

Abstract: In this paper, we fabricate a surface acoustic wave (SAW) device with micro-structures on a zinc oxide (ZnO) thin film and measure its signal response. The manufacturing processes of the SAW device include the fabrication of micro-structures of a SAW element and its interdigital transducer by silicon micro-machining and the fabrication of a thin film of ZnO by RF magnetron sputtering. We, then, measure the SAW properties. This research investigates the properties of sputtered thin films for various amounts of O2/(Ar + O2) using Zn and ZnO targets. Regardless of target, the growth rate of the ZnO thin film decreases as the oxygen content increases. When the SAW is sputtered ZnO thin film using 30% oxygen, the digital signal of the SAW has better performance. The measurement signal of the SAW with micro-structures is similar to that without micro-structures.

Optimal configuration of the waveguide acousto-optic TE-TM polarization mode convertor on X-cut lithium niobate substrate

Abstract: An excitation, distribution, and interaction of surface acoustic waves (SAW) with the guided light in integrated optical structures on X-cut lithium niobate substrates were studied. The resonance excitation frequencies, the spatial SAW distribution and the TE-TM optical mode conversion efficiency were investigated. An optimal configuration and most suited material of interdigital transducer (IDT) for integrated acousto-optic devices were found.

Generation and enhancement of surface acoustic waves on a highly doped p-type GaAs substrate

Abstract: Surface acoustic waves (SAWs) have been widely studied due to their unique advantage to couple the mechanical, electrical, and optical characteristics of semiconductor materials and have successfully been used in many industrial applications. In this work, we report a design that uses piezoelectric material Zinc Oxide (ZnO) to enhance the generation and propagation of SAWs on the surface of a highly doped p-type Gallium Arsenide (GaAs) substrate, which is more extensively used in optoelectronic devices than intrinsic GaAs structures. To maximize the piezoelectricity and successfully generate SAWs, high quality c-axis orientation of the ZnO film is needed; thus we experiment and develop optimized recipes of a radio frequency (RF) magnetron sputtering system to deposit ZnO on the GaAs substrate. To further optimize the SAW performance, an intermediate Silicon Oxide (SiO2) layer is added between the ZnO film and GaAs substrate. Additionally, we test samples with varied thickness of ZnO films and dimensions of interdigital transducer (IDT) fingers to figure out their individual effect on SAW properties. The results and techniques demonstrated in this paper will provide guidance for further studies on enhancing SAWs propagating along many other doped semiconductor materials. This combination of acoustics and optoelectronics in doped semiconductors is a promising start to building enhanced and hybrid devices in various fields.

Acoustic wave device, high frequency front end circuit, and communication apparatus

Abstract: An elastic wave device includes a piezoelectric substrate and an interdigital transducer electrode on the piezoelectric substrate, the piezoelectric substrate including a piezoelectric layer and a high-acoustic-velocity member layer, the piezoelectric layer being stacked on the high-acoustic-velocity member layer. The piezoelectric layer is made of lithium tantalate. Denoting an elastic wave propagation direction as a first direction, and a direction perpendicular or substantially perpendicular to the first direction as a second direction, a central region, low-acoustic-velocity regions, and high-acoustic-velocity regions are provided in the interdigital transducer electrode in the second direction. The low-acoustic-velocity regions include mass-adding films on electrode fingers. Denoting a film thickness normalized to a wavelength determined by the electrode finger pitch of the interdigital transducer electrode as a wavelength-normalized film thickness (%), a product of the wavelength-normalized film thickness of the mass-adding films and the density (g/cm3) of the mass-adding films is about 13.4631 or less.

Capability of LiTaO 3 /Quartz HAL SAW Resonators Confirmed by Simulation and Measurement

Abstract: This paper reports hetero acoustic layer (HAL) surface acoustic wave (SAW) resonators using a thin LiTaO 3 (LT) plate with negative TCF and a quartz substrate with positive TCF. In the previous study, a high impedance (Z) ratio (82 dB), an excellent temperature coefficient of frequency (TCF: 2 ppm/°C), and spurious-free characteristic up to 14 GHz were demonstrated. In this study, two kinds of LT/ quartz HAL SAW resonators with different wavelengths of interdigital transducer (IDT) were fabricated, and measured results were compared with simulated ones. The measured bandwidths (BWs) roughly agreed with the simulated ones. Although many measured values of Z ratios are lower than the simulated ones, the best Z ratios among them are similar to the simulated ones. This result is reasonable taking account of the imperfectness of laboratory-level fabrication, and suggests that the simulation in this study well predicts the performance of real devices.

Surface acoustic wave device

Abstract: A surface acoustic wave device (10) is provided with a piezoelectric substrate (24), a plurality of functional elements (30) formed on the piezoelectric substrate (24), a cover section (20) arranged so as to face the piezoelectric substrate (24) with a support layer (22) therebetween, and input/output terminals (28) arranged on the cover section (20) An IDT (interdigital transducer) electrode is included in at least some of the plurality of functional elements (30) and a surface acoustic wave resonator is formed by the piezoelectric substrate (24) and the IDT electrodes The plurality of functional elements (30) includes a filter unit (100) through which a signal in a predetermined frequency band is made to pass and a cancel circuit (110) that is connected in parallel to the filter unit (100) and that attenuates signals outside of the range of the predetermined frequency band in signals output from the output terminal (28) A part (32) of a wiring pattern connecting a first functional element and a second functional element included in the plurality of functional elements (30) is formed on the cover section (20)

Finite element simulation of one-port surface acoustic wave resonator with thick interdigital transducer for gas sensing

Abstract: The paper presents finite element simulation of a surface acoustic wave (SAW) one-port resonator with thick interdigital transducers (IDT) made of nickel metal for sensing dimethyl methylphosphonate (DMMP) gas by placing fluoroalcoholpolysiloxane (SXFA) sensing film in the space between thick IDT fingers. The absorption of DMMP gas changes density and thickness of SXFA film and affect the SAW propagation velocity, hence resonance frequency of the device. The change in resonance frequency is measured as sensor response. In this paper individual effects of change in density and thickness of SXFA film due to absorption of DMMP gas on sensor response are simulated. The results show that the change in thickness of the SXFA film placed in the space between thick IDT fingers of proposed device is dominant in sensor response and the sensitivity of the proposed device (2.1 kHz/mg/m3) is about 3.2 times greater than a conventional device using SXFA coated over the entire top surface of the device.