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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; Li, Andrew; Heilman, Grant D.; Garcia, Isaac; Menk, Lyle Alexander; Balakrishnan, Ganesh; Sinno, Talid; Han, Sang M. (January 2021, Applied physics letters)

   null (Ed.)

   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 e_14 piezoelectric coefficient, which is shown to increase linearly with temperature. Using the extracted e_14, 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. 62.6 GHz ScAlN solidly mounted acoustic resonators

   https://doi.org/10.1063/5.0306947  

   Wang, Yinan; Kim, Byeongjin; Ravi, Nishanth; Saha, Kapil; Dasgupta, Supratik; Chulukhadze, Vakhtang; Kwon, Eugene; Matto, Lezli; Simeoni, Pietro; Barrera, Omar; et al (January 2026, Applied Physics Letters)

   We demonstrate a record-high 62.6 GHz solidly mounted acoustic resonator (SMR) incorporating a 67.6 nm scandium aluminum nitride (Sc0.3Al0.7N) piezoelectric layer on a 40 nm buried platinum (Pt) bottom electrode, positioned above an acoustic Bragg reflector composed of alternating SiO2 (28.2 nm) and Ta2O5 (24.3 nm) layers in 8.5 pairs. The Bragg reflector and piezoelectric stack above are designed to confine a third-order thickness-extensional bulk acoustic wave mode, while efficiently transducing with thickness-field excitation. The fabricated SMR exhibits an extracted piezoelectric coupling coefficient (k2) of 0.8% and a maximum Bode quality factor (Q) of 51 at 63 GHz, representing the highest operating frequency reported for an SMR to date. These results establish a pathway toward mmWave SMR devices for filters and resonators in next-generation RF front ends. 

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5. 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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