Ústav mikroelektroniky
Browse
Recent Submissions
Now showing 1 - 5 of 207
- ItemElectrical properties of epoxy/graphite flakes microcomposite at the percolation threshold concentration(IOP Publishing Ltd, 2024-04-17) Alsoud, Ammar Awadallah Ahmad; Daradkeh, Samer; Shaheen, Adel A; Al-Hroub, Qasim Amjad; Knápek, Alexandr; Mousa, Marwan; Sobola, DinaraThe electrical properties and activation energy of epoxy/graphite flakes (GFs) micro-composite with different content of GFs (0.0625-1 wt%) were studied for electrical properties using Novocontrol Alpha Analyser (10-2 Hz-107 Hz). GFs sizes ranged from (100 nm to 10 mu m). The analysis was performed by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), visible spectrum reflectance spectra (VIS) spectra, and Fourier Transform Infrared spectra (FTIR) spectroscopy. Increasing GFs content caused multiple changes in electrical characteristics. At 0.0625 wt%, all electrical properties noticeably increased. But at 0.125 to 0.25 wt%, immobilized nanolayers were formed leading to decreased permittivity, dielectric loss (tan(delta)), quality factor (Q-factor), capacitance, conductivity, and figure of merit (F-factor). At 0.25 wt%, the epoxy microcomposite had lower permittivity, tan(delta), conductivity, and capacitance compared with unfilled epoxy. With 0.5 wt% of GFs, signified the percolation threshold, initiating a rise in permittivity, conductivity, capacitance, and tan(delta), accompanied by the closer proximity of grain boundaries, facilitating the formation of conductive channels. At a concentration of 1 wt% of GFs, the establishment of continuous interfacial conductive pathways resulted in a remarkable augmentation of all dielectric properties. The Cole-Cole analysis has been employed to investigate variations in epoxy/GFs microcomposites based on concentration levels.
- ItemAutomatic test-bench for SiC power devices using LabVIEW(SLOVAK UNIV TECHNOLOGY, 2024-04-01) Leuchter, Jan; Pham, Ngoc Nam; Nguyen, Huy HoangThis paper is devoted to the improvement existing models of electronics devices, which are used in powers electronics as switching devices, and investigate a LabVIEW-based automatic test-bench for Silicon carbide (SiC) power devices. In recent years, power electronic devices are required to be capable handle with higher voltage, leads to development of new generation of power electronic devices, such as SiC devices. However, using a simulation platform, such as Spice, to diminish the complexity of power electronic design with these new devices is hindered by the lack of precise models. The proposed test-bench enables not only measuring static characteristics of SiC power devices, but also extracting key parameters required by simulations. These extracted parameters are then employed in the existing device model, and the simulation results which are based on the model with original parameters and models with extracted parameters are compared with measured results. The comparison clearly demonstrates that parameters obtained from the proposed test-bench significantly enhance the Spice model.
- ItemComparative Analysis of Energy Storage and Buffer Units for Electric Military Vehicle: Survey of Experimental Results(MDPI, 2024-01-23) Pham, Ngoc Nam; Bloudíček, Radim; Leuchter, Jan; Rydlo, Stanislav; Dong, Quang HuyThis paper deals with the analyses of batteries used in current military systems to power the electric drives of military vehicles. The article focuses on battery analyses based on operational data obtained from measurements rather than analyses of the chemical composition of the tested batteries. The authors of the article used their experience from the development test-laboratory of military technology. This article presents a comparative analysis of existing and promising technologies in the field of energy storage and buffering for military electric vehicles. The overview of these technologies, including the design, operating principles, advantages, and disadvantages, are briefly presented to produce theoretical comparative analyses. However, this article mainly focuses on the experimental verification of operational ability in varied conditions, as well as the comparison and analysis of these results. The main part of the article provides more experimental studies on technologies of energy storage and buffering using the results of several experiments conducted to demonstrate the behavior of each technology in different working conditions. The output parameters, as well as the state of charge of each technology's samples, were surveyed in various temperatures and loading characteristics. The results presented in this paper are expected to be useful for optimizing the selection of energy storage and buffering solutions for military electric vehicles in different applications and functional environments.
- ItemCleaning of tungsten tips for subsequent use as cold field emitters or STM probes(FEI STU, 2024-01-31) Košelová, Zuzana; Horáková, Lenka; Burda, Daniel; Allaham, Mohammad Mahmoud; Knápek, Alexandr; Fohlerová, ZdenkaThis study investigates the crucial process of cleaning cold field emission electron emitters and scanning tunnel microscopy (STM) probes, particularly focusing on tungsten tips. The cleanliness of these tips is essential for maintaining optimal cathode properties, preventing impurities that can significantly affect the emission process. Various cleaning methods, including macroetching, ammonia cleaning, and hydrofluoric acid (HF) cleaning were explored and compared by scanning electron microscopy. The macroetching method, involving a mixture of hydrochloric acid, nitric acid, and hydrogen fluoride, proved to be too reactive, causing significant material removal and altering the tip's structure. Ammonia cleaning did not significantly improve or harm the samples. However, oxide islands appeared in some areas, suggesting the potential formation of ammonium tungsten oxide. HF cleaning, specifically at 20% and 50% concentrations, demonstrated effectiveness in removing tungsten oxides without damaging the tip. Pre-cleaning with water and ethanol proved beneficial for subsequent HF refinement. Results suggest that HF is the most suitable method for oxide removal but a rinse with water is essential for removing residual sodium hydroxide. To maintain optimal properties, it is crucial to apply a less reactive layer quickly or transfer the tips to a water/ethanol bath to prevent oxidation.
- Item0.5-V High Linear Fully Differential Multiple-Input Bulk-Driven OTA With Effective Self-Embedded CMFB(IEEE, 2024-05-06) Khateb, Fabian; Kulej, Tomasz; Kumngern, Montree; Prommee, PipatThis paper presents a new fully differential multiple-input operational transconductance amplifier (FD MI-OTA) with an effective self-embedded common-mode feedback circuit (CMFB). The circuit employs several design techniques to extend the linearity to the rail-to-rail level, such as a bulk-driven, multiple-input capacitive voltage divider and source degeneration. The circuit uses self-cascode transistors to increase the gain of the OTA from one side and to create a common-mode feedback circuit, needed to control the common-mode output voltage from the other side. Thus, the CMFB is part of the OTA and as a result, its chip area and power consumption remain unchanged. The performance of the proposed circuit was simulated using TSMC's CMOS $0.18 \, \mu \text{m}$ process in the Cadence Virtuoso System Design Platform to validate the performance of the topology. Intensive simulation results based on Monte Carlo and process, voltage, temperature corners were performed to confirm the OTA's performance and the robustness of the CMFB. The circuit operates with a supply voltage of 0.5 V and consumes 17.5nW of power, making it suitable for applications with extremely low voltage supply and low frequency. As an application, a second-order low-pass filter was designed based on the proposed FD MI-OTA.