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- ItemSpectroscopic 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, AlexandrGraphite-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.
- ItemField 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, PavelThis 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.
- ItemComparative analysis of surface layer functionality in STM and AFM probes: Effects of coating on emission characteristics(SLOVAK UNIV TECHNOLOGY, 2024-08-01) Knápek, Alexandr; Allaham, Mohammad Mahmoud; Košelová, Zuzana; Burda, Daniel; Podstránský, Jáchym; Mousa, Marwan S. Mousa; Sobola, DinaraThis study compares different types of scanning probe microscopy (SPM) probes according to the function of the surface layer at the tip apex. Three main types of SPM probes were analyzed: scanning tunneling microscopy (STM) tungsten probes, conductive atomic force microscopy (AFM) probes, and non-conductive AFM probes. The tungsten STM probes were coated with a graphite layer to simulate the effects of carbonization. The tested AFM probes were specifically NenoProbe conductive AFM probes (platinum-coated tip) and Akiyama non-conductive AFM probes coated with gold. The gold coating is intended to improve surface conductivity and help achieve a homogeneous, oxidation-resistant surface. The three samples were measured in a field emission microscope to study their current-voltage characteristics. The obtained current-voltage characteristics were tested and analyzed by the Forbes field emission orthodoxy test, providing the field emission parameters that correlate with the state of the scanning probe tip. In this study, the most important parameter is the formal emission area parameter, which indicates the formal tunneling current density through the probe tip-sample nanogap. For an STM tip, this reflects the size and shape of the region from which electrons tunnel to the sample surface. If this area is larger than expected or desired, it may indicate problems with tip function or tip wear. This information is critical for evaluating the performance and accuracy of the STM tip and can help diagnose problems and optimize its function.
- ItemThe electrical and dielectric features of Al/YbFeO3/p-Si/Al and Al/YbFe0.90Co0.10O3/p-Si/Al structures with interfacial perovskite-oxide layer depending on bias voltage and frequency(Springer Nature, 2024-06-01) Coskun, Mustafa; Polat, Özgür; Orak, Ikram; Coskun, F.M.; Yildirim, Yucel; Sobola, Dinara; Sen, Cengiz; Durmuş, Zehra; Caglar, Yasemin; Caglar, Mujdat; Turut, AbduelmecitIn this investigation, thin films of YbFeO3, both in its pure form and doped with 10% Co, were fabricated on a p-Si substrate at 500 degrees C through the radio-frequency magnetron sputtering method. Examination via Scanning Electron Microscopy demonstrated a porous texture for the pure sample, contrasting with a smooth and crack-free surface post-Co doping. Analysis via X-ray photoelectron spectroscopy unveiled Yb's 3 + oxidation state, alongside the presence of lattice oxygen, oxygen vacancies, and adsorbed oxygen evident in Gaussian fitting curves. Photoluminescence spectroscopy revealed an augmented emission intensity, likely attributed to increased defect initiation in the Co-doped specimen. Moreover, Raman spectroscopy was employed to identify vibration modes in the examined samples, demonstrating shifts in Raman peaks indicative of Co substitution and subsequent distortion in the crystal structure of YbFeO3. Electrical assessments were conducted at room temperature (300 K) under ambient conditions, employing voltage and frequency as variables. Capacitance-voltage measurements illustrated the emergence of an accumulation, with depletion and inversion regions manifesting at different frequencies based on the applied voltage, attributed to the YbFeO3 interfacial layer at the Al and p-Si interface. The conductance-voltage characteristics indicated that the structure exhibited maximum conductance in the accumulation region. Series resistance for these configurations was deduced from capacitance-conductance-voltage measurements, indicating a dependence on both bias voltage and frequency. The doping process led to a reduction in capacitance and series resistance, accompanied by an increase in conductance values. After obtaining corrected capacitance and conductance parameters, it became evident that series resistance significantly influences both parameters. Interface state density (N-ss), determined through the Hill-Coleman relation demonstrated a decreasing trend with increasing frequency. The pure sample exhibited higher interface state density compared to the Co-doped sample at each frequency, highlighting that the 10% Co-doped YbFeO3 thin film enhances the quality of the metal-semiconductor interface properties compared to the pure contact.
- ItemCurrent applications and challenges of the Internet of Things(Vilnius Gediminas Technical University, 2023-04-11) Dallaev, Rashid; Pisarenko, Tatiana; Talu, Stefan; Sobola, Dinara; Majzner, Jiří; Papež, NikolaThe concept of the Internet of Things is capable of making a giant leap in the economy, including research in the field of computer science, network technologies, microelectronics and sensor technology. Combined with the technological developments of nanotechnology and robotics, IoT can play a central role in the industrial revolution by creating economic relations between machines and connecting the economy of people and machines, solving a number of problems that humanity is facing. All devices controlled via the Internet are elements of the Internet of things. The IoT has allowed various possibilities for all countries to improve life quality and the technological ideas for efficiency, productivity, security, and profit. An integrated security system is a giant step towards the improved economy. The concept of IoT plays a decisive role in the further development of the infocommunication industry. This is confirmed both by the position of the International Telecommunication Union (ITU) and the European Union on this issue, and by the inclusion of the Internet of Things in the list of breakthrough technologies in the United States, China and other countries. Thus, this article will go over the current state of the IoT as well as describe which devices and industries stand to benefit from the advantages it brings. Additionally, statistical data on the actual trends and investments into IoT across the world are also provided.