Pressure sensing with zero group velocity lamb modes in self-supported a-SiC/c-ZnO membranes

Abstract

The propagation of the Lamb modes along a-SiC/ZnO thin supported composite structures was simulated for different ZnO and a-SiC layer thicknesses and electrical boundary conditions. The phase and group velocity, the field profile and the electroacoustic coupling coefficient dispersion curves of the Lamb modes travelling along the composite plate were calculated for different layers thicknesses. Zero group velocity (ZGV) points were identified which group velocity vanishes while the phase velocity remains finite, at specific layers thickness values. ZGV resonators (ZGVRs) were designed that consist in only one interdigital transducer (IDT) and no grating reflectors at its sides. The finite element method analysis was performed to investigate the strain, stress and internal pressure the a-SiC/ZnO plate experiences when subjected to an external uniform differential pressure in the 1 to 10 kPa range. The ZGVR pressure sensitivity, i.e. the relative frequency shift per unit pressure change, was found to be mostly affected by the change in the membrane thickness induced by the pressure. A pressure sensitivity of 9 ppm/kPa, in the 4 to 10 kPa range, was predicted for the a-SiC(1μm)/ZnO(1μm) ZGV-based pressure sensor. The feasibility of high-frequency micropressure sensors based on a-SiC and ZnO thin film technology was demonstrated by the present simulation study. order in which they appear along the frequency axis. All the modes are dispersive as their velocity depends on the plate thickness-to-wavelength ratio H/λ, and some modes have group and phase velocities with opposite signs. For some branches of the angular frequency dispersion curves, ω vs k, a strong resonance occurs at the frequency minimum corresponding to a zero-group velocity (ZGV) Lamb mode: this stationary non-propagating mode is characterized by a vanishing group velocity v gr = ω/k combined with a non-zero wave number k [4][5][6][7][8]. The ZGV points appear in the frequency spectrum of both monolayer (isotropic and anisotropic) and multilayer plates. Depending on the plate material type and crystallographic orientation, in addition to modes with a single ZGV point, some modes exhibit double and even multiple such points [9] as their dispersion curve undergoes multiple changes in the sign of its slope. If the composite waveguide consists in a piezoelectric layer (such as ZnO or AlN) and a non-piezoelectric layer, the Lamb wave propagation can be excited and detected by use of interdigitated transducers (IDTs), as for the surface acoustic waves (SAWs). The IDTs can be either positioned onto the free surface of the piezoelectric layer or buried under the piezoelectric layer, thus allowing the exploitation of different electroacoustic coupling configurations.ZGV resonators (ZGVRs) are associated with an intrinsic energy concentration beneath the IDT. Due to the vanishing group velocity, the acoustic energy cannot be carried away from the IDT, leading to a stationary non-propagating mode. They can be fabricated with a technology simpler than that requir...

The 2019 surface acoustic waves roadmap

“…Acoustic reflection was shown to be nonlinear; and an excited qubit was shown to relax by emitting SAWs. The next development was the construction of SAW cavities with high Q-values (~10 5 ) [33], shorted IDTs were used as efficient acoustic mirrors. It was later shown that superconducting qubits could be placed inside these resonators (see figure 3) and strong interaction was observed [34,35].…”

“…1 Institute of Physics, University of Augsburg, 86159 Augsburg, Germany 2 University of Göttingen, 3rd Institute of Physics-Biophysics, 37077 Göttingen, Germany 3 Center for NanoScience (CeNS), Ludwig-Maximilians-Universität Munich, 80799 Munich, Germany 4 Center for Interdisciplinary Health Research (ZIG), University of Augsburg, 86135 Augsburg, Germany 5 Augsburg Center for Innovative Technologies (ACIT), Augsburg 86159, Germany 6 Nanosystems Initiative Munich (NIM), Munich, Germany…”

“…The special issue comprises topical reviews and research articles from leading experts from the entire field on novel sensors [4,5] waveguide modulators [6], single quantum dot (QD) structures [7][8][9][10] 2D materials [11][12][13][14][15][16] piezoelectric materials and hybrid devices [17][18][19][20][21][22][23][24], and even macroscopic quantum systems [25,26].…”

Higher-order Lamb waves with quasi-zero surface displacement components on a GaAs piezoelectric plate

“…For example, QZ-PAW will have lower sensitivity but a wider dynamic range for highly viscous media than QL-LW for viscosity sensors. Furthermore, QZ-PAW can be used for a physical sensor that affects the elasticity constant of the whole plate, such as temperature, strain and pressure sensor [27,28].…”

Progress of One-Dimensional SiC Nanomaterials: Design, Fabrication and Sensing Applications

“…The propagation of the Lamb modes along a-SiC/c-ZnO thin supported composite structures by different ZnO and a-SiC layer thicknesses and electrical boundary conditions was simulated by Caliendo. A pressure sensitivity of 9 ppm kPa −1 , in the 4–10 kPa range, was predicted for the a-SiC/ZnO ZGV (Zero Group Velocity) based pressure sensor [ 123 ]. A SiC and aluminum nitride-based DTMCPS (Double Touch Mode Capacitive Pressure Sensor) with a substrate notch was explored.…”