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Author: Karnaushenko, Dmitriy D. × Author: Ma, Libo × Author: Schmidt, Oliver G. × End date: 2024 × Start date: 2020 ×

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    Wafer-Scale High-Quality Microtubular Devices Fabricated via Dry-Etching for Optical and Microelectronic Applications
    (Weinheim : Wiley-VCH, 2020) Saggau, Christian N.; Gabler, Felix; Karnaushenko, Dmitriy D.; Karnaushenko, Daniil; Ma, Libo; Schmidt, Oliver G.
    Mechanical strain formed at the interfaces of thin films has been widely applied to self-assemble 3D microarchitectures. Among them, rolled-up microtubes possess a unique 3D geometry beneficial for working as photonic, electromagnetic, energy storage, and sensing devices. However, the yield and quality of microtubular architectures are often limited by the wet-release of lithographically patterned stacks of thin-film structures. To address the drawbacks of conventionally used wet-etching methods in self-assembly techniques, here a dry-release approach is developed to roll-up both metallic and dielectric, as well as metallic/dielectric hybrid thin films for the fabrication of electronic and optical devices. A silicon thin film sacrificial layer on insulator is etched by dry fluorine chemistry, triggering self-assembly of prestrained nanomembranes in a well-controlled wafer scale fashion. More than 6000 integrated microcapacitors as well as hundreds of active microtubular optical cavities are obtained in a simultaneous self-assembly process. The fabrication of wafer-scale self-assembled microdevices results in high yield, reproducibility, uniformity, and performance, which promise broad applications in microelectronics, photonics, and opto-electronics. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Imperceptible Supercapacitors with High Area-Specific Capacitance
    (Weinheim : Wiley-VCH, 2021) Ge, Jin; Zhu, Minshen; Eisner, Eric; Yin, Yin; Dong, Haiyun; Karnaushenko, Dmitriy D.; Karnaushenko, Daniil; Zhu, Feng; Ma, Libo; Schmidt, Oliver G.
    Imperceptible electronics will make next-generation healthcare and biomedical systems thinner, lighter, and more flexible. While other components are thoroughly investigated, imperceptible energy storage devices lag behind because the decrease of thickness impairs the area-specific energy density. Imperceptible supercapacitors with high area-specific capacitance based on reduced graphene oxide/polyaniline (RGO/PANI) composite electrodes and polyvinyl alcohol (PVA)/H2SO4 gel electrolyte are reported. Two strategies to realize a supercapacitor with a total device thickness of 5 µm—including substrate, electrode, and electrolyte—and an area-specific capacitance of 36 mF cm−2 simultaneously are implemented. First, the void volume of the RGO/PANI electrodes through mechanical compression is reduced, which decreases the thickness by 83% while retaining 89% of the capacitance. Second, the PVA-to-H2SO4 mass ratio is decreased to 1:4.5, which improves the ion conductivity by 5000% compared to the commonly used PVA/H2SO4 gel. Both advantages enable a 2 µm-thick gel electrolyte for planar interdigital supercapacitors. The impressive electromechanical stability of the imperceptible supercapacitors by wrinkling the substrate to produce folds with radii of 6 µm or less is demonstrated. The supercapacitors will be meaningful energy storage modules for future self-powered imperceptible electronics.