The metal-to-insulator transition of VO 2 underpins applications in thermochromics, neuromorphic computing, and infrared vision. Ge alloying is shown to elevate the transition temperature by promoting V–V dimerization, thereby expanding the stability of the monoclinic phase to higher temperatures. By suppressing the propensity for oxygen vacancy formation, Ge alloying renders the hysteresis of the transition exquisitely sensitive to oxygen stoichiometry.
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Abstract The characteristic metal–insulator phase transition (MIT) in vanadium dioxide results in nonlinear electrical transport behavior, allowing VO2devices to imitate the complex functions of neurological behavior. Chemical doping is an established method for varying the properties of the MIT, and interstitial dopant boron has been shown to generate a unique dynamic relaxation effect in individual B‐VO2particles. This paper describes the first demonstration of an electrically stimulated B‐VO2proto‐device which manifests a time‐dependent critical transformation temperature and switching voltage derived from the coupling of dopant diffusion dynamics and the metal–insulator transition of VO2. During quasi‐steady current‐driven transitions, the electrical responses of B‐VO2proto‐devices show a step‐by‐step progression through the phase transformation, evidencing domain transformations within individual particles. The dynamic relaxation effect is shown to increase the critical switching voltage by up to 41% (Δ
V crit= 0.13 V) and also to increase the resistivity of the M1 phase of B‐VO2by 14%, imbuing a memristive response derived from intrinsic material properties. These observations demonstrate the dynamic relaxation effect in B‐VO2proto‐devices whose electrical transport responses can be adjusted by electronic phase transitions triggered by temperature but also by time as a result of intrinsic dynamics of interstitial dopants. -
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Textured surfaces are commonly designed to preclude wetting by water. The design of surfaces that are not wetted by alcohols represents a considerable challenge given the low surface tension, viscosity, and density of these liquids. Herein, a hierarchically textured plastronic architecture that can suspend alcohol droplets in a metastable Cassie–Baxter regime is presented. As a result of microtexturation of the underlying stainless steel mesh, multiscale texturation derived from ZnO tetrapods, and surface functionalization with perfluorinated‐polyhedral oligomeric silsesquioxanes, the surfaces glide aliphatic alcohols, water, and
n ‐hexadecane. The design of surfaces not wetted by alcohols is particularly relevant to “point‐of‐care” environments. Because of the minimized interfacial contact areas, the textured surfaces further greatly inhibit ice nucleation at solid/liquid interfaces. High‐speed video imaging of the freezing and droplet impact shows that the textured surfaces delay ice nucleation by inhibiting heterogeneous nucleation, more effectively channel kinetic energy upon droplet impact to break up impinging droplets, and greatly limit frost formation. Once ice forms, its adhesion is substantially diminished by about three orders of magnitude as compared with planar substrates. The results demonstrate a scalable spray deposition method to generate surfaces for enabling the deterministic flow of liquids as well as inhibit ice formation.
