Ústav mikroelektroniky

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Spectroscopic study for the role of polymer binding agent in the quasi-harmonic field emission behavior of polymer graphite field emission cathodes
(IOP Publishing Ltd, 2025-02-17) Allaham, Mohammad Mahmoud; Daradkeh, Samer Issa Abdel Razzaq; Košelová, Zuzana; Dallaev, Rashid; Sobola, Dinara; Knápek, Alexandr
Graphite-based microcathodes have shown significant performance when operated as cold field emission electron sources. Specifically mentioned, cathodes that have been prepared from highly ordered pyrolytic graphite and polymer graphite pencil leads. Such cathodes are characterized by low operating voltages, a long lifetime, a cheap fabrication price, and a stable emission current. Recently, it was shown that polymer graphite cold field emission cathodes have a unique quasi-harmonic field emission behavior, where the process included emission of pulses of electrons with relatively higher emission current values. However, this behavior has not been reported for other graphite-based materials. In this paper, we study the effects of the polymer binding agent on the charge carriers' flow through the surface of polymer graphite using Raman-current spectroscopy. The results from polymer graphite were then compared to cathodes prepared from colloidal graphite conductive paint when deposited on a glass substrate. The results showed that the I(D)/I(G) ratio of polymer graphite had a fluctuating behavior, which was not the case for colloidal graphite, which had a more stable structure.
The impact of single and combined amendment of elemental sulphur and graphene oxide on soil microbiome and nutrient transformation activities
(Elsevier Ltd, 2024-10-15) Hammerschmiedt, Tereza; Holátko, Jiří; Bytešníková, Zuzana; Škarpa, Petr; Richtera, Lukáš; Kintl, Antonín; Pekárková, Jana; Kučerík, Jiří; Jaskulska, Iwona; Radziemska, Maja; Valová, Radmila; Malíček, Ondřej; Brtnický, Martin
Background: Sulphur (S) deficiency has emerged in recent years in European soils due to the decreased occurrence of acid rains. Elemental sulphur (S0) is highly beneficial as a source of S in agriculture, but it must be oxidized to a plant-accessible form. Micro- or nano-formulated S0 may undergo accelerated transformation, as the oxidation rate of S0 indirectly depends on particle size. Graphene oxide (GO) is a 2D-carbon-based nanomaterial with benefits as soil amendment, which could modulate the processes of S0 oxidation. Micro-and nano-sized composites, comprised of S0 and GO, were tested as soil amendments in a pot experiment with unplanted soil to assess their effects on soil microbial biomass, activity, and transformation to sulphates. Fourteen different variants were tested, based on solely added GO, solely added micro- or nano-sized S0 (each in three different doses) and on a combination of all S0 doses with GO. Results: Compared to unamended soil, nano-S0 and nano-S0+GO increased soil pH(CaCl2). Micro-S0 (at a dose 4 g kg1) increased soil pH(CaCl2), whereas micro-S0+GO (at a dose 4 g kg1) decreased soil pH(CaCl2). The total bacterial and ammonium oxidizer microbial abundance decreased due to micro-S0 and nano-S0 amendment, with an indirect dependence on the amended dose. This trend was alleviated by the co-application of GO. Urease activity showed a distinct response to micro-S0+GO (decreased value) and nano-S0+GO amendment (increased value). Arylsulfatase was enhanced by micro-S0+GO, while sulphur reducing bacteria (dsr) increased proliferation due to high micro-S0 and nano-S0, and co-amendment of both with GO. In comparison to nano-S0, the amendment of micro-S0+GO more increased soluble sulphur content more significantly. Conclusions: Under the conditions of this soil experiment, graphene oxide exhibited a significant effect on the process of sulphur oxidation.
Field Ion Microscopy of Tungsten Nano-Tips Coated with Thin Layer of Epoxy Resin
(MDPI, 2024-10-09) Sobola, Dinara; AL Soud, Ammar; Knápek, Alexandr; M. Hamasha, Safeia; Mousa, Marwan S. Mousa; Schubert, Richard; Kočková, Pavla; Škarvada, Pavel
This paper presents an analysis of the field ion emission mechanism of tungsten-epoxy nanocomposite emitters and compares their performance with that of tungsten nano-field emitters. The emission mechanism is described using the theory of induced conductive channels. Tungsten emitters with a radius of 70 nm were fabricated using electrochemical polishing and coated with a 20 nm epoxy resin layer. Characterization of the emitters, both before and after coating, was performed using electron microscopy and energy-dispersive X-ray spectroscopy (EDS). The Tungsten nanocomposite emitter was tested using a field ion microscope (FIM) in the voltage range of 0-15 kV. The FIM analyses revealed differences in the emission ion density distributions between the uncoated and coated emitters. The uncoated tungsten tips exhibited the expected crystalline surface atomic distribution in the FIM images, whereas the coated emitters displayed randomly distributed emission spots, indicating the formation of induced conductive channels within the resin layer. The atom probe results are consistent with the FIM findings, suggesting that the formation of conductive channels is more likely to occur in areas where the resin surface is irregular and exhibits protrusions. These findings highlight the distinct emission mechanisms of both emitter types.
0.5 V, Low-Power Bulk-Driven Current Differencing Transconductance Amplifier
(MDPI, 2024-10-25) Kumngern, Montree; Khateb, Fabian; Kulej, Tomasz
This paper presents a novel low-power low-voltage current differencing transconductance amplifier (CDTA). To achieve a low-voltage low-power CDTA, the BD-MOST (bulk-driven MOS transistor) technique operating in a subthreshold region is used. The proposed CDTA is designed in 0.18 mu m CMOS technology, can operate with a supply voltage of 0.5 V, and consumes 1.05 mu W of power. The proposed CDTA is used to realize a current-mode universal filter. The filter can realize five standard transfer functions of low-pass, band-pass, high-pass and band-stop, and all-pass from the same circuit. Neither component-matching conditions nor input signals of the inverse type are required to realize these filter functions. The current-mode filter offers low-input and high-output impedance and uses grounded capacitors. The natural frequency and quality factor of the filters can be orthogonally controlled. The proposed CDTA and its applications are simulated using SPICE to confirm the feasibility and functionality of the new circuits.
Exploring the Frontiers of Cell Temperature Measurement and Thermogenesis
(WILEY, 2024-10-28) Zhu, Hanliang; Xu, Haotian; Zhang, Yue; Brodský, Jan; Gablech, Imrich; Korabečná, Marie; Neužil, Pavel
The precise measurement of cell temperature and an in-depth understanding of thermogenic processes are critical in unraveling the complexities of cellular metabolism and its implications for health and disease. This review focuses on the mechanisms of local temperature generation within cells and the array of methods developed for accurate temperature assessment. The contact and noncontact techniques are introduced, including infrared thermography, fluorescence thermometry, and other innovative approaches to localized temperature measurement. The role of thermogenesis in cellular metabolism, highlighting the integral function of temperature regulation in cellular processes, environmental adaptation, and the implications of thermogenic dysregulation in diseases such as metabolic disorders and cancer are further discussed. The challenges and limitations in this field are critically analyzed while technological advancements and future directions are proposed to overcome these barriers. This review aims to provide a consolidated resource for current methodologies, stimulate discussion on the limitations and challenges, and inspire future innovations in the study of cellular thermodynamics.

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