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1. High-Temperature Piezoelectric Characterization of Gallium Arsenide and Surface Acoustic Wave Analysis via Interdigitated Transducer Modeling

   Rummel, Brian D; Miroshnik, Leonid; Hellman, Grant D; Garcia, Isaac; Menk, Lyle Alexander; Balakrishnan, Ganesh; Sinno, Talid; Han, Sang M. (January 2021, Applied physics letters)

   Interdigitated transducer devices provide an advantageous platform to study stress-enhanced interfacial phenomena at elevated temperatures but require a thorough understanding of temperature-dependent material properties. In this study, the temperature dependence of the piezoelectric coefficient for gallium arsenide is determined from 22 ℃ to 177 ℃. Experimental scattering parameter responses are measured for a two-port surface acoustic wave resonator at different temperatures and piezoelectric coefficient values are extracted using a frequency-domain finite element method simulation. Device measurements are taken using an interdigitated transducer fabricated on semi-insulating GaAs(100), oriented in the 〈110〉 direction and device resonant frequencies are shown to decrease with increasing temperature. The experimental scattering response is used to reconcile the simulated scattering response and extract the 𝑒14 piezoelectric coefficient, which is shown to increase linearly with temperature. Using the extracted 𝑒14, surface acoustic wave analysis is completed to study the magnitude of bulk stress values and surface displacement over the experimental temperature range produced by a standing surface acoustic wave field. Surface displacement measurements are taken at room temperature using contact-mode AFM, which corroborate the simulation predictions. The modeling results demonstrate an interdigitated transducers potential as an experimental stage to study surface and bulk stress effects on temperature-sensitive phenomena. 

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2. Exploring electromechanical utility of GaAs interdigitated transducers; using finite-element-method-based parametric analysis and experimental comparison

   https://doi.org/10.1116/6.0002169  

   Rummel, Brian D.; Miroshnik, Leonid; Li, Andrew B.; Heilman, Grant D.; Balakrishnan, Ganesh; Sinno, Talid; Han, Sang M. (January 2023, Journal of Vacuum Science & Technology B)

   Analysis of interdigitated transducers often relies on phenomenological models to approximate device electrical performance. While these approaches prove essential for signal processing applications, phenomenological models provide limited information on the device’s mechanical response and physical characteristics of the generated acoustic field. Finite element method modeling, in comparison, offers a robust platform to study the effects of the full device geometry on critical performance parameters of interdigitated transducer devices. In this study, we fabricate a surface acoustic wave resonator on semi-insulating GaAs [Formula: see text], which consists of an interdigitated transducer and acoustic mirror assembly. The device is subsequently modeled using fem software. A vector network analyzer is used to measure the experimental device scattering response, which compares well with the simulated results. The wave characteristics of the experimental device are measured by contact-mode atomic force microscopy, which validates the simulation’s mechanical response predictions. We further show that a computational parametric analysis can be used to optimize device designs for series resonance frequency, effective coupling coefficient, quality factor, and maximum acoustic surface displacement. 

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3. Direct Measurement of Inverse Piezoelectric Effects in Thin Films Using Laser Doppler Vibrometry

   https://doi.org/10.1103/PhysRevApplied.20.014017  

   Acharya, Megha; Lou, Djamila; Fernandez, Abel; Kim, Jieun; Tian, Zishen; Martin, Lane W (July 2023, Physical Review Applied)

   Further miniaturization of electronic devices necessitates the introduction of new materials, including piezoelectric thin films, that exhibit electromechanical functionalities without significant degradation in response due to substrate-induced clamping. To identify material systems with superior piezoelectric properties as thin films, simplified and quantitative electromechanical characterization techniques are required. Here, single-beam, laser Doppler vibrometry is used to detect ac electric-field-induced surface displacement in the frequency range 1–100 kHz with low error (around 6% at 10 kHz) and resolution of 0.0003 nm. The technique is used to quantify both electrostriction and piezoelectric responses (surface displacement values <0.05 nm) of various thin films. Requirements for sample geometry and device structures are established and measurement accuracy and resolution are validated against measurements from the literature via synchrotron-based diffraction measurements. A general methodology to measure and extract the piezoelectric coefficients for thin-film samples using finite-element modeling is presented and applied to determine the d33 coefficient and visualize the response in substrate-clamped 50–400-nm-thick PbZr0.52Ti0.48O3 films, especially as compared to bulk versions with the same sample geometry. 

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4. Droplet delivery and nebulization system using surface acoustic wave for mass spectrometry

   https://doi.org/10.1039/D0LC00495B  

   Sun, Di; Böhringer, Karl F.; Sorensen, Matthew; Nilsson, Erik; Edgar, J. Scott; Goodlett, David R. (August 2020, Lab on a Chip)

   We present a piezoelectric transducer for standing wave surface acoustic wave nebulization (SW-SAWN) patterned with anisotropic ratchet conveyors (ARCs) to automate the sample preparation and droplet delivery. 

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5. Electromechanical Brillouin scattering in integrated planar photonics

   https://doi.org/10.1063/1.5108672  

   Li, Huan; Liu, Qiyu; Li, Mo (August 2019, APL Photonics)

   The exploitation of Brillouin scattering, the scattering of light by sound, has led to demonstrations of a broad spectrum of novel physical phenomena and device functionalities for practical applications. Compared with optomechanical excitation by optical forces, electromechanical excitation of acoustic waves with transducers on a piezoelectric material features intense acoustic waves sufficient to achieve near-unity scattering efficiency within a compact device footprint, which is essential for practical applications. Recently, it has been demonstrated that gigahertz acoustic waves can be electromechanically excited to scatter guided optical waves in integrated photonic waveguides and cavities, leading to intriguing phenomena such as induced transparency and nonreciprocal mode conversion, and advanced optical functionalities. The new integrated electromechanical Brillouin devices, utilizing state-of-the-art nanofabrication capabilities and piezoelectric thin film materials, succeed guided wave acousto-optics with unprecedented device integration, ultrahigh frequency, and strong light-sound interaction. Here, we experimentally demonstrate large-angle (60°) acousto-optic beam deflection of guided telecom-band light in a planar photonics device with electromechanically excited gigahertz (∼11 GHz) acoustic Lamb waves. The device consists of integrated transducers, waveguides, and lenses, all fabricated on a 330 nm thick suspended aluminum nitride membrane. In contrast, conventional guided-wave acousto-optic devices can only achieve a deflection angle of a few degrees at most. Our work shows the promises of such a new acousto-optic device platform, which may lead to potential applications in on-chip beam steering and routing, optical spectrum analysis, high-frequency acousto-optic modulators, RF or microwave filters and delay lines, as well as nonreciprocal optical devices such as optical isolators. 

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