SAW Propagation Research Articles

Measuring of the surface acoustic wave amplitude in the X-112° Y-cut of a LiTaO3 crystal using X-ray diffraction at the laboratory X-ray source

The SAW excitation and propagation on the X-112° Y-cut of a LiTaO3 crystal were studied using a triple-axis X-ray diffractometer with a laboratory X-ray source. Simulation of X-ray rocking curves with the Takagi equation system enabled the determination of surface acoustic wave amplitudes on the crystal surface. The SAW excitation process in the frequency range of an acoustoelectronic device, determined by the excitation band or interdigital transducer structure, was studied.

Analysis of Sezawa mode Rayleigh-type SAWs on ScAlN film/floated electrode layer/ScAlN film/high velocity substrates

Surface acoustic wave (SAW) devices for frequency filters are increasingly required to have high performance in future mobile communications. The coupling factors K 2 for Rayleigh-type SAW (RSAW) on ScAlN film/high velocity substrate structures can be enhanced by introducing polarization-reversal structure into the ScAlN film. However, the growth of polarization-reversal ScAlN films with high crystal orientation would be very difficult. In this study, the Sezawa mode RSAWs on layered structures consisting of ScAlN films with floated intermediate electrode layer/high velocity substrates were analyzed by using Farnell and Adler’s SAW propagation analysis and finite element method. We found that the K 2 values of the Sezawa modes were enhanced by inserting the floated intermediate electrode layer without using polarization reversal structure, which were higher than those of the polarization-reversal ScAlN films/high velocity substrates. The enhancement of K 2 would be due to the improvement of the SAW energy concentration at the ScAlN film surface.

Experimental Study of Deep Submersible Structure Defect Monitoring Based on Flexible Interdigital Transducer Surface Acoustic Wave Technology.

In view of the shortage of structural defect monitoring methods for deep submersibles, numerical simulation and experimental research on underwater SAW propagation based on interdigital transducers are carried out in this paper. PVDF interdigital transducer (PVDF-IDT) has shown considerable potential in the application of structural health monitoring because of its micro size, soft material characteristics, and the characteristics of long-term bonding on the surface of the tested structure. In order to realize the application of IDT on submersible or underwater structures, it is necessary to understand the influence of underwater environment on IDTs with different structures. The underwater attenuation of IDT with 2-5 mm wavelength and the underwater attenuation of Lamb (A0 mode) wave on a 4 mm thick titanium alloy plate is obtained through COMSOL software simulation. The experimental verification shows that the simulation results match with the actual situation, which proves that COMSOL software can accurately calculate the acoustic attenuation of surface waves at the solid-liquid interface. At the same time, the underwater attenuation of IDT with different structures is very different, providing important design parameters for the underwater interdigital transducer. In this paper, it is found that the Lamb wave has significant advantages over the Rayleigh wave in the health monitoring of underwater thin plate structures.

FEM Analysis of Various Multilayer Structures for CMOS Compatible Wearable Acousto-Optic Devices.

Lately, wearable applications featuring photonic on-chip sensors are on the rise. Among many ways of controlling and/or modulating, the acousto-optic technique is seen to be a popular technique. This paper undertakes the study of different multilayer structures that can be fabricated for realizing an acousto-optic device, the objective being to obtain a high acousto-optic figure of merit (AOFM). By varying the thicknesses of the layers of these materials, several properties are discussed. The study shows that the multilayer thin film structure-based devices can give a high value of electromechanical coupling coefficient (k2) and a high AOFM as compared to the bulk piezoelectric/optical materials. The study is conducted to find the optimal normalised thickness of the multilayer structures with a material possessing the best optical and piezoelectric properties for fabricating acousto-optic devices. Based on simulations and studies of SAW propagation characteristics such as the electromechanical coupling coefficient (k2) and phase velocity (v), the acousto-optic figure of merit is calculated. The maximum value of the acousto-optic figure of merit achieved is higher than the AOFM of all the individual materials used in these layer structures. The suggested SAW device has potential application in wearable and small footprint acousto-optic devices and gives better results than those made with bulk piezoelectric materials.

Robust, high-resolution, indexed 3D slowness surfaces for Rayleigh-type waves on Lithium Niobate via parallelised Newtonian flow phase tracking

Micro-Electromechanical System Surface Acoustic Wave (MEMS SAW) devices are key technological enablers in RF telecommunications filters, inertial systems and biosensors. Recent developments in Focused SAW (FSAW) device design demand high quality, high resolution dispersion data for multiple in-plane directions, typically presented as a slowness curve, to facilitate design. Very few slowness curves are available in the literature for free surfaces not aligned to the crystallographic axes except in a few special cases. The first major novelty in the present work is a bespoke computational approach to solving this problem with a distinct theoretical basis. After a brief summary of the motivation, the mathematical formulation and its theoretical footing are outlined. The most important algorithms are given as pseudocode, and source code, datasets and extended visualisation available online are referenced. The structure of the method is illustrated via application to the bulk wave problem. The model is then applied to Lithium Niobate to generate new results characterising SAW propagation velocity for all in-plane directions over one full circle of plane inclinations. These results are presented as a two-dimensional velocity surface. This new data constitutes the second area of novelty herein. Finally, the applicability of the work to FSAW design is indicated by examining the RMS variation of propagation velocity for different cut plane inclinations.

Specific features of SH-waves propagation in structures with prestressed inhomogeneous coating made of piezoceramics based on LiNbO3

Within the framework of the linearized theory of electroelastic wave propagation, a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a symmetry class of 3m is considered. The ferroelectric LiNbO3 is used as the main material of the structure. The initial deformed state of the coating material is homogeneous, induced by the action of initial mechanical stresses and an external electrostatic field, the properties of the coating continuously change in thickness. By the example of the problem of the propagation of SH-waves from a remote source for structures with an inhomogeneous prestressed coating in the case of an electrically free and short-circuited surface, the influence of the nature and localization of the inhomogeneity of the coating on the features of SAW propagation is studied. The separate and combined effects of initial actions on changes in the physical properties of the structure, the transformation of the surface wave field, and the change in the SAW velocities in a wide frequency range is studied. The results obtained in this work are useful for understanding the dynamic processes in prestressed piezoelectric structures, in the optimization and design of new structures and devices on SAW with high performance characteristics.

Electrically Tunable Surface Acoustic Wave Propagation at MHz Frequencies Based on Carbon Nanotube Thin‐Film Transistors

AbstractSurface acoustic waves (SAWs) that propagate on the surface of a solid at MHz frequencies are widely used in sensing, communication, and acoustic tweezers. However, their properties are difficult to be tuned electrically, and current devices suffer from complicated configurations, complicated tuning mechanisms, or small ranges of tunability. Here a structure featuring a thin‐film transistor configuration is proposed to achieve electrically tunable SAW propagation based on conductivity tuning. When a DC gate voltage is applied, the on‐site conductivity of the piezoelectric substrate is modulated, which leads to velocity and amplitude tuning of SAWs. The use of carbon nanotubes and crystalline nanocellulose as the channel and gate materials results in high tuning capacity and low gate voltage requirement. The tunability is manifested by a 2.5% phase velocity tuning and near 10 dB on/off switching of the signals. The proposed device holds the potential for the next generation SAW‐based devices.

2E1-3 Theoretical analysis of Rayleigh SAW propagation characteristics on YbAlN films/ high velocity substrates

2E1-3 Theoretical analysis of Rayleigh SAW propagation characteristics on YbAlN films/ high velocity substrates

1Pa3-2 SAW Propagation Properties of (K,Na)NbO3 Films Deposited by Hydrothermal Synthesis or RF Sputtering

1Pa3-2 SAW Propagation Properties of (K,Na)NbO₃ Films Deposited by Hydrothermal Synthesis or RF Sputtering

Influence of an Electrostatic Field on Saw in Prestressed Ferroelectric Heterostructures

An approach to modeling a ferroelectric heterostructure with a prestressed coating made of a two-component functional-gradient material is proposed. Various types of PZT-based ceramics with close values of elastic moduli and significant differences in piezoelectric and dielectric parameters are considered as coating materials. The initial stress state (ISS) of the coating is caused by the action of an electric field and uniaxial mechanical tension. By the example of the problem of the propagation of sh-waves, the influence of the initial electrostatic field on the features of the SAW propagation has been investigated for various ratios of the parameters of the coating materials and the nature of the inhomogeneity localization.

FEM simulation analysis of TiO2/ZnO/SiO2/Si multilayer structure for CMOS compatible acousto-optic tunable filter

In this paper, TiO2/ZnO/SiO2/Si layer structures with different thickness of ZnO and TiO2 is discussed and explained. The study is carried out in order to obtain optimal normalized thickness of the multilayer structure for fabricating acousto-optic tunable filter with high figure of merit (FOM). Based on simulation and study of SAW propagation characteristics like, electromechanical coupling co-efficient, figure of merit and phase velocity, it is inferred that this structure is suitable for the desired application.

Influence of the anisotropy on the magneto-acoustic response of magnetic surface acoustic wave resonators**Project supported by the National Natural Science Foundation of China (Grant No. 61871081) and the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 51827802).

One-port magnetic surface acoustic wave (MSAW) resonators are fabricated by stacking multilayered (FeCoSiB/SiO2)n films directly on top of interdigital electrodes. It is shown that the magneto-acoustic response of the MSAW resonators critically depends the hysteresis of ΔE effect. For the magnetic multilayer without induced magnetic anisotropy, the resonance frequency (fR) exhibits a butterfly-like dependence on the external field, therefore, enabling bipolar detection of magnetic field smaller than its coercive field. However, for the magnetic multilayers with induced magnetic anisotropy, butterfly-like or loop-like fR–H curves are measured along the interdigtial electrode fingers or the SAW propagation direction, which can be attributed to the competition between the magnetic field-induced anisotropy and the stress-induced or shape anisotropy.

Analysis of longitudinal leaky surface acoustic wave propagation characteristics on a piezoelectric ScAlN layer/sapphire or quartz substrate

Longitudinal leaky surface acoustic wave (LLSAW) modes with a high phase velocity are suitable for high-frequency SAW filter applications. However, their attenuation is higher than that of other SAW modes, causing a small Q factor. On the other hand, a low attenuation and high coupling factor K2 in LLSAWs on a piezoelectric thin plate/high-velocity sapphire or quartz substrate have been demonstrated theoretically and experimentally. We expected that LLSAWs propagating on a highly piezoelectric ScAlN layer/sapphire or quartz substrate also have a high phase velocity, high K2 and low attenuation. In this study, the characteristics of LLSAWs on ScAlN layer/sapphire or quartz substrates were theoretically investigated. The cut angle and SAW propagation direction of quartz substrates strongly affect the attenuation of LLSAWs on the layered structure. We found that a LLSAW resonator with (0° 90° 90°) Sc0.4Al0.6N layer/X-cut 30° Y propagation quartz has a high Q factor and high K2, which is adequate for SAW filter applications.

Corrigendum: Visualization of Surface Acoustic Waves in Thin Liquid Films.

Scientific Reports 6: Article number: 21980; Published online: 26 February 2016; Updated: 13 May 2016 This Article contains errors in the Results section under subheading ‘Measurement of anisotropy and focal point’, “The literature value41 for the SAW propagation velocity was fitted with a parabolicfunction 48 with the velocity v, the propagation angle ϕ towards the x direction and the anisotropy factor b.

Theoretical Analysis of SAW Propagation in 3C-SiC/c-AlN

The anisotropic materials as the acoustic wave propagating medium introduce the dependence of the phase velocity on the wave propagation direction, as opposed to the isotropic counterparts; in addition, the profile of the particle displacement components can be quite different, depending on the crystal type and propagation direction. The propagation of surface and bulk acoustic waves (SAWs and BAWs) along the (001), (111) and (110) planes of cubic SiC crystals have been studied. For specific propagation directions in these planes, slight variations in the velocity of the elastic surface waves are found. It was observed that Rayleigh-type, generalized and pseudo-surface waves can propagate at specific directions, thus confirming how the anisotropic behavior of the bare SiC substrate modifies the existence and the field profile of the SAW that propagates at its free surface. Finally, the SAW propagation along AlN/SiC-based multilayered structures is studied for the three SiC planes, different AlN piezoelectric layer thicknesses and electrical boundary conditions.

Graphitized Layer Buried in a Diamond: SAW Generation under Picosecond Optical Excitation

The excitation of SAW was detected on diamond with built-in ion-implanted graphitized layer under its illumination with femtosecond laser pulses. The spectral width of a SAW pulses were in the range of 1.5÷2 GHz. It was found out that the anisotropy of the SAW propagation was practically absent. The increase in the implantation dose from 4·1015 cm−2 to 12·1015 cm−2 was shown to give rise to a dispersion of SAW propagation.

Probing Quantum Hall State Homogeneity with Surface Waves

We study single quantum wells and matched density bilayer samples. Simultaneous measurements of the Hall voltages using low frequency lock-in techniques and of the changes in the 232 MHz (12.6 μm) SAW propagation measured with a vector network-analyzer allow comparison of the complex bulk and edge conductivities. The vtotal = 1 bilayer state is seen directly in the SAW measurement only when the conductivity is below ~ 6 × 10−7 Siemens and is destroyed at moderate SAW powers by localized heating. The simultaneous reduction of the conductivity minima extracted from Hall data and from SAW data conclusively demonstrates that the vtotal = 1 state disappears simultaneously throughout the bulk and not by the formation of competing domains or conducting filaments.

Analysis of Mass Loading Effect on Guided Shear Horizontal Surface Acoustic Wave on Liquid/Au/Quartz Structure for Biosensor Application

A numerical analysis of a shear horizontal surface acoustic wave (SH-SAW) immunoassay biosensor has been investigated. The numerical calculation method proposed by Campbell and Jones has generally been used to calculate SAW propagation characteristics. In this paper, a numerical calculation method for SH-SAW propagation characteristics, which is a modified method of Campbell and Jones involving the effect of liquid viscosity is applied to quartz. A mass loading sensitivity of a 250 MHz SH-SAW delay-line biosensor was calculated and compared with the experimental results. It can be concluded from the results that viscosity sensitivity is dominant over mass loading sensitivity for 250 MHz SH-SAW biosensors.

Correlation between propagation loss and silicon dioxide film properties for surface acoustic wave devices

The correlation between the propagation loss and SiO2 film properties has been studied for temperature-compensated SAW devices using the SiO2/LiNbO3 structure. The SAW devices were prepared under different deposition temperatures for SiO2 film. Although they possessed excellent temperature coefficient of elasticity characteristics, devices prepared at lower temperature showed lower Q-factors. The SiO2 films were also deposited on a Si substrate under the same deposition conditions used for the SAW device preparation. Optical characterization was performed with Fourier transform infrared spectroscopy (FT-IR), spectrometer measurement, and Raman spectroscopy. IR absorbance spectra were almost same in the FT-IR measurement. However, optical attenuation in the UV region decreased with the deposition temperature in the spectrometer measurement. The optical attenuation is caused by the increase of the extinction coefficient in the SiO2 layer, and its optical wavelength dependence indicated that observed excess attenuation is caused by Rayleigh scattering. The Raman scattering also decreased with the deposition temperature in the Raman spectroscopy. The scattering is caused by the distortion of the SiO2 network. These results indicate that the Rayleigh scattering caused by the distortion of the SiO2 network is the main contributor to the excess SAW propagation loss in this case.

A full set of langatate high-temperature acoustic wave constants: elastic, piezoelectric, dielectric constants up to 900°c

A full set of langatate (LGT) elastic, dielectric, and piezoelectric constants with their respective temperature coefficients up to 900°C is presented, and the relevance of the dielectric and piezoelectric constants and temperature coefficients are discussed with respect to predicted and measured high-temperature SAW propagation properties. The set of constants allows for high-temperature acoustic wave (AW) propagation studies and device design. The dielectric constants and polarization and conductive losses were extracted by impedance spectroscopy of parallel-plate capacitors. The measured dielectric constants at high temperatures were combined with previously measured LGT expansion coefficients and used to determine the elastic and piezoelectric constants using resonant ultrasound spectroscopy (RUS) measurements at temperatures up to 900°C. The extracted LGT piezoelectric constants and temperature coefficients show that e11 and e14 change by up to 62% and 77%, respectively, for the entire 25°C to 900°C range when compared with room-temperature values. The LGT high-temperature constants and temperature coefficients were verified by comparing measured and predicted phase velocities (vp) and temperature coefficients of delay (TCD) of SAW delay lines fabricated along 6 orientations in the LGT plane (90°, 23°, Ψ) up to 900°C. For the 6 tested orientations, the predicted SAW vp agree within 0.2% of the measured vp on average and the calculated TCD is within 9.6 ppm/°C of the measured value on average over the temperature range of 25°C to 900°C. By including the temperature dependence of both dielectric and piezoelectric constants, the average discrepancies between predicted and measured SAW properties were reduced, on average: 77% for vp, 13% for TCD, and 63% for the turn-over temperatures analyzed.