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Two typographical corrections are made for our recently published paper [Opt. Mater. Express12(7),2529(2022)10.1364/OME.462592]. The results, discussion, and conclusion of the paper are unaffected.

 

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. 

Scales ofCyphochiluswhite beetles present one of the strongest optical scattering materials in nature. However, the intricate optical fibrillar network nanostructure inside the scales has been difficult to mimic. Here, characteristic structural parameters insideCyphochilusscales – mean fiber diameter, diameter distribution, filling fraction, and structural anisotropy – are replicated in synthetic nanofibrous materials to functionally mimic the biological material. To fabricate the synthetic nanostructure, electrospinning is chosen because this conventional technique is amenable to nanomanufacturing. The optimized parameters in electrospun structures are found to be only slightly different from those inCyphochilusscales. At the optimum, electrospun structures exhibit even stronger optical scattering thanCyphochilusscales. An electrospun film with the similar characteristic structural parameters as those inCyphochilusscales gives two resonance peaks in visible reflectance spectrum in the limit of a uniform fiber diameter, giving a purple structural color. As the distribution of diameter increases appreciably to experimentally achievable degrees, the resonance peaks broaden and the reflectance spectrum becomes relatively flat, resulting in disappearance of the structural color. These results support that controllable fibrous nanostructures that exceed the exceptionally strong broadband optical scattering found among living organisms can be volume-produced.

 

Free energy functionals of the Ginzburg–Landau type lie at the heart of a broad class of continuum dynamical models, such as the Cahn–Hilliard and Swift–Hohenberg equations. Despite the wide use of such models, the assumptions embodied in the free energy functionals frequently either are poorly justified or lead to physically opaque parameters. Here, we introduce a mathematically rigorous pathway for constructing free energy functionals that generalizes beyond the constraints of Ginzburg–Landau gradient expansions. We show that the formalism unifies existing free energetic descriptions under a single umbrella by establishing the criteria under which the generalized free energy reduces to gradient-based representations. Consequently, we derive a precise physical interpretation of the gradient energy parameter in the Cahn–Hilliard model as the product of an interaction length scale and the free energy curvature. The practical impact of our approach is demonstrated using both a model free energy function and the silicon–germanium alloy system. 

Cyphochiluswhite beetle scales exhibit exceptionally strong light scattering power that originates from their regular random fibrillar network nanostructure. The structure is believed to be formed by late-stage spinodal decomposition in a lipid membrane system. However, the structure is characterized by nonconstant mean curvatures and appreciable anisotropy, which are not expected from late-stage spinodal decomposition, so that the surface free energy is not minimized. Nevertheless, a high degree of regularity represented by the relatively uniform fibril dimensions and smooth fibril surfaces in the structure may result from a process similar to spinodal decomposition. In this study, we investigate the role of regularity in theCyphochiluswhite beetle scale structure in realizing strong light scattering. Irregularity is computationally introduced into the structure in a systematic fashion such that its anisotropy is preserved and its surface area is kept constant. Calculations show that optical scattering power decreases as irregularity increases with a high sensitivity. This effect happens because, remarkably, irregularity on a scale much smaller than the wavelength destroys anisotropy in optical diffusion. Thus, the result shows that thein vivoprocess inCyphochiluswhite beetle scales utilizes structural regularity and anisotropy to achieve strong light scattering at a tolerable surface free energy. In typical fabrication of random media, irregularity and multiple length scales typically increase surface area, so that durability of the nanostructures may be negatively affected. Our study indicates that regularity in anisotropic random nanostructures can achieve strong light scattering with a moderate surface free energy.

 

Arsenic’s high vapor pressure leads to thermal instability during hightemperature processing of GaAs, contributing to the performance degradation of subsequently fabricated devices. The resulting surface damage also obfuscates the exact quantitative characterization of the diffusion process, a critical step in device manufacturing. In this experiment, an encapsulant-and-sacrificial-layer procedure is employed to reduce arsenic sublimation and preserve a smooth surface. A capped GaAs/InGaAs/GaAs quantum well structure is subjected to rapid thermal annealing, and AFM, SEM, and EDS are used to compare the surface qualities of the postannealed encapsulated GaAs against the reference GaAs. For the encapsulated substrate, a smooth surface with an average root-mean-squared value of 6.5 Å is achieved after high-temperature processing. SIMS analysis is used to obtain the diffused indium atomic concentration profiles for a smooth and roughened GaAs surface and their corresponding diffusion parameters. The analysis demonstrates how precise diffusion parameter extraction requires preserving an atomically-smooth surface in semiconductor diffusion characterization. 

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. 

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.