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Porous-anodic-alumina-templated Ta-Nb-alloy oxide coatings via the magnetron-sputtering anodizing as novel 3D nanostructured electrodes for energy-storage applications
(Elsevier, 2024-06-26) Mozalev, Alexander; Bendová, Mária; Gispert-Guirado, Francesc; Llobet, Eduard; Habazaki, Hiroki
The Ta-Nb thin alloy films were magnetron sputter-deposited over a low-aspect-ratio nanoporous anodic-alumina template formed in 0.05 M tartaric acid solution at 250 V and modified by the pore-widening technique to enlarge the pores up to 500 nm. The alloy coated the pores evenly, thus forming a 3D continuous conducting nanofilm on the template. Partially anodizing the templated alloy in a borate buffer solution of pH 7.5 generated a compact amorphous mixed-oxide anodic film thickening proportionally to the applied voltage. An unusual two-layered structure with a sharp electrical interface revealed in the 3D oxide films anodized to 30–130 V, comprising a low-resistivity layer superimposed on the high-resistivity layer, is explained by an immobile negative space charge in the outer film part. The air-annealing at moderate temperatures releases the space charge and transforms the two layers into a high-resistivity single layer having substantially improved dielectric properties and thermostable (up to 250 deg) capacitance of 1.2 F cm2 achieved for the film anodized to practical 50 V. The 3D films having up to 4.5 times enlarged effective surface area can be utilized as novel metal/oxide nanostructured electrodes for electrolytic microcapacitors suitable for classical electronic circuits and energy-storage applications.
Asynchronous delta-sigma modulator in 28 nm FDSOI technology
(ELSEVIER - DIVISION REED ELSEVIER INDIA PVT LTD, 2024-09-02) Kledrowetz, Vilém; Fujcik, Lukáš; Prokop, Roman; Háze, Jiří
A novel solution of the first-order asynchronous delta-sigma modulator (ADSM) is proposed. The circuit designed for the commercial temperature range (0 degrees C to 70 degrees C) in a 28 nm fully depleted silicon on insulator (FD-SOI) technology from STMicroelectronics. This technology allows designing new subcircuit topologies, resulting in an ADSM that offers a 64.2 dB signal-to-noise and distortion ratio ( SNDR ) corresponding to 10.37-bit resolution in the signal bandwidth of 10 kHz. The ADSM consumes 4.1 mu W at a power supply of V, and the obtained power efficiency is 0.15 pJ/conversion. The ADSM occupies an area of only 0.0042 mm(2).
The collective photothermal effect of silver nanoparticles probed by a microbolometer
(Springer Nature, 2024-05-01) Zhu, Hanliang; Gablech, Evelína; Gablech, Imrich; Neužil, Pavel
Nanoparticles have become a significant area of research, offering properties that bridge the gap between bulk materials and atomic structures. Silver nanoparticles (AgNPs), specifically, have shown promise due to their plasmonic properties. Despite extensive studies, capturing the photon-to-heat conversion efficiency of individual nanoparticles has been challenging. Here, we present an approach to determine these properties using an ultra-sensitive bolometer with a power resolution of 26pW. Our investigations reveal that a single AgNP can dissipate power with a magnitude between 101.3 fW and 205.3 fW, an observation that underscores the potential of these particles for efficient energy conversion. This finding enhances the understanding of AgNPs’ behavior and pushes the field of nanoparticle plasmon physics forward. Therefore, the refined use of such nanoparticles could bring advancements across a range of applications, from high-resolution imaging and advanced spectroscopy to environmental surveillance and innovative medical treatments.
Comprehensive analysis of charge carriers dynamics through the honeycomb structure of graphite thin films and polymer graphite with applications in cold field emission and scanning tunneling microscopy
(ELSEVIER, 2024-09-13) Allaham, Mohammad Mahmoud; Daradkeh, Samer; Al-Braikat, Hatem; Dallaev, Rashid; Burda, Daniel; Košelová, Zuzana; Al-Akhras, M-Ali; Jaber, Ahmad; Mousa, Marwan; Sobola, Dinara; Kolařík, Vladimír; Knápek, Alexandr
Polymer graphite electron sources have performed satisfactorily as field emission emitters and scanning tunneling microscopy probes in the past few years. However, the emission process was characterized by limited total emission currents. This paper introduces the elemental, vibrational, electronic structure, and optical analysis of polymer graphite and glass-graphite composite field emission cathodes to study these limitations. Moreover, the field emission characteristics are studied including the changes in the potential energy barrier of the used materials and structures. Among the studied structures, the cathodes prepared from graphite thin films deposited on a micropointed glass substrate (film-GMF) showed superior performance as random field emission arrays. This includes obtaining much higher emission current values 20 times) and lower threshold voltages 1/2) compared to the results obtained from polymer graphite samples. The enhancement factor in such emitters is believed to be the three-dimensional honeycomb structure of graphite. Moreover, the study includes applying graphite coatings to tungsten nano-field emission cathodes and scanning tunneling microscopy probes, which improves the performance of such cathodes/probes in both microscopic techniques.
XPS characterization of metal-oxide nanocolumn arrays via anodizing Al/Nb/Mo metal layers
(TANGER LTD, 2024-01-01) Bendová, Mária; Prášek, Jan; Mozalev, Alexander
Molybdenum oxides exhibit numerous electronic properties thanks to the ability of Mo to possess various oxidation states and coordinations. Molybdenum oxides are thus attractive for applications in energy storage, conversion, electrochromic, gas sensing, or superconducting devices. The nanostructuring of molybdenum oxides, controlled through the preparation conditions, is advantageous for enhancing the material's properties. The so-called porous-anodic-alumina (PAA)-assisted anodizing, based on the anodic oxidation of a metal layer through a PAA overlayer, may also be a way to grow molybdenum-oxide nanocolumn arrays if their stability in water-containing electrolytes can be secured. To take on the challenge, we envisioned mixing MoOx with the oxide of a different metal (Nb), by placing a thin interlayer of Nb between the Al and Mo in the precursor thin-film stack. The arrays were prepared from the magnetron-sputtered Al/Nb/Mo trilayers by anodizing at 46 V, then re-anodizing to 180 V, followed by selective dissolution of the PAA overlayer. Detailed XPS characterization confirmed that various Mo species were present in the column material, with a total amount of Mo reaching 16 at.% (Mo+Nb = 100%). The fitting of the narrow-scan Nb 3d and Mo 3d spectra showed that Mo6+, Mo5+, and Mo4+, in various ratios, were present at the column surface material, whereas Nb2O5 was almost entirely stoichiometric. Further investigation is underway to understand the formation-structure-morphology relationship and explore the functional properties of the novel nanoarrays.

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