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Monel (R) alloy 400 has excellent corrosion resistance and finds applications in marine industries. The processing of marine components requires high processing efficiency and a quality finish. Hence, this research aims to investigate the effects of the laser processing parameters such as laser fluence, scanning velocity, hatching distance, and the scanning pass on the ablation rates and efficiency, chemistry, and nanomechanical properties of the Monel (R) alloy 400 after pulsed picosecond (ps) laser ablation. From the experimental findings, the ablation depth increases as the laser fluence increases while decreasing as the scanning velocity increases. Surface roughness was noted to increase as the laser fluence increased. The findings demonstrated that the ablation rate increases as laser fluence increases while ablation efficiency decreases. Energy dispersive x-ray spectroscopy (EDX) showed that the elemental composition of laser-ablated zones is almost similar to that of the polished sample. X-ray spectroscopy (XPS) shows that the outer layer on the surface of Monel (R) alloy 400 is composed of NiO and CuO. The hardness and Young's modulus of the laser-processed alloy were found to be less than those of the bulk material. This study can be used to establish optimal processing parameters for the ultrafast ps laser processing of materials to achieve high ablation efficiency with a high-quality surface finish for industrial applications.

This 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.

The 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.

This paper reports results of analysis of field ion emission mechanism from tungstenepoxy composite emitters that are compared to tungsten nanofield emitters. In this context, the mechanism of emission from this type of emitters is described based on a theory of induced conductive channels. The tungsten emitters were prepared using the electrochemical polishing technique and coated with a layer of the epoxy resin. Field ion microscope (FIM) analyses are reported including the study of the emissionion density distributions from both the uncoated and coated emitters. Two forms of emission patterns have been observed in the ion emission microscopy technique describing the differences in the emission mechanism of both types of emitters. The observed results show: (a) the expected crystalline surface atomic distribution images of the field ion microscopy in the case of uncoated tungsten tips, and (b) randomly distributed emission spots that describe the locations of the induced conductive channels inside the resin coating layer.

Surface structuring by ultrafast lasers is a promising technique to modify surface-related properties of materials to tailor them for specific applications. In the present study, we experimentally investigated the laser structuring of commercially pure titanium (CP Ti) using ultrafast pulses to understand the role of the laser input parameters on the development of surface morphology, optical properties, surface chemistry, and wettability behaviour. The processed surfaces were characterized by a scanning electron microscope, energy-dispersive X-ray spectroscopy (EDX), Raman microscope, optical microscope, and sessile drop method. Laser-induced periodic surface structures decorated with nanodroplets were noted to be formed on the surface of the laser-structured CP Ti. The surface roughness measurements showed that the laser-structured surfaces had nanoscale roughness values. The EDX and the Raman analyses show that laser-structured surfaces of CP Ti have a thin oxide film. Different colours on different surfaces processed by different laser parameters were observed. The wettability assessment shows that CP Ti can transition from hydrophilic-hydrophobic and vice versa depending on the environmental conditions. This study shows that laser structuring can be utilized to modify CP Ti surfaces to obtain desirable surface properties that can find potential applications in different fields.

The absorption coefficient is an important optical property in characterizing semiconducting materials. It plays a significant role in studying optical characteristics, electrical structure, energy band structure, and the creation/annihilation of excitons when a semiconducting material absorbs electromagnetic radiation. In this study, an enhanced theoretical model will be introduced and applied to characterize thin films prepared from UPR4 (unsaturated polyester resin) single-component epoxy resin, which is important to study the charge flow at the interface of tungsten-UPR4 composite field emission cathodes.

The absorption coefficient plays an important role in studying and characterizing semiconducting materials. It is an important parameter to study the mechanism of photons absorption within the structure of the studied material. Thus, it helps to study the several types of charge carrier transport along with the energy band structure and its defects. In literature, a formula was reported to precisely calculate the absorption coefficient from raw data of transmittance and reflectance of electromagnetic radiation. However, the reported formula has several issues limiting its validity in the literature. In this paper, we provide a more mathematically accurate form of this equation to precisely obtain the absorption coefficient from the raw data, by considering the total internal reflection at the different interfaces. Moreover, the equation is tested by simulated data and is applied to study the optical characteristics of a single-component epoxy resin from its transmittance and reflectance raw data.

In this study, modified epoxy nanocomposite was produced by incorporating SiO2 nanoparticles of 15–30 nm in size, with different concentrations ranging from 1 to 20 wt%. The electrical properties of the epoxy nanocomposite were measured at room temperature in the frequency range of 102–107 Hz. To determine the impact of nanoparticles on the epoxy composition, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS), Fourier transform infrared spectra (FTIR) spectroscopy, and Raman spectroscopy were conducted. With an increase in filler (SiO2 nanoparticles) content, the electrical characteristics of the epoxy nanocomposite exhibited multiple changes. At low concentrations, all electrical properties experienced a notable increase. The epoxy with 15 wt% of SiO2 nanoparticles samples had a lower permittivity, loss number, conductivity, and capacitance than the unfilled epoxy. At medium concentrations (5 to 15 wt%), the formation of immobilized nanolayers has an impact on permittivity, loss number, conductivity, and capacitance, which have decreased; impedance and modulus increased. The initiation of contact between the nanofillers at a concentration of 20 wt% leads to the formation of continuous interfacial conductive pathways, resulting in a dramatic increase in the permittivity, conductivity, and capacitance of the composites, while concurrently reducing impedance.

This paper studies the performance of differenttypes of graphite cathodes when operated as field emissionelectron sources. The tested cathodes were prepared in theform of bulk polymer graphite, bulk pure graphite, and polymergraphite coated with thin layer of insulating material(epoxy resin). The obtained results include X-Ray photoelectronspectroscopy analysis, scanning electron micrographs, the fieldemission microscope patterns and current-voltage characteristics,and the orthodoxy test analysis results. The importance of thisstudy is summarized in following the pursuit of finding cheapand green electron sources. Moreover, to present a new exoticfield emission behavior in the form of emission pulses.

In the presented work, we report the dielectricbehavior of epoxy–silicon oxide composites in the temperaturerange 240– 300 K, over the frequency range 10-2 Hz – 107 Hz. Themeasuring apparatus was based on the Novocontrol AlphaAnalyser and the measured data were analyzed and interpretedusing the Havriliak – Negami equation. The master curves of thereal part of permittivity and the dielectric loss number wereobtained by time–temperature superposition principle, and theresults showed that the nano-composite had a much higher lossfactor. Through the analysis of the origin of the dielectric responsein epoxy/silica composite, the reason for the different dielectricrelaxation behaviors of the nano-composite, and the pure epoxywas discussed.

In field electron emission (FE) studies, interpretation of measured current–voltage characteristics and extraction of emitter characterization parameters are usually carried out within the framework of “smooth planar metal-like emitter (SPME) methodology”, using a data-analysis plot. This methodology was originally introduced in the 1920s. Three main data-plot types now exist: Millikan–Lauritsen (ML) plots, Fowler–Nordheim (FN) plots, and Murphy–Good (MG) plots. ML plots were commonly used in early FE studies, but most modern analysis uses FN plots. MG plots are a recent introduction. Theoretically, it is now known that ML and FN plots are predicted to be slightly curved in SPME methodology, but a Murphy–Good plot will be very nearly straight. Hence (because 1956 Murphy–Good emission theory is “better physics” than 1928 Fowler–Nordheim emission theory as corrected in 1929), expectation is that parameter extraction using a MG plot will be more precise than extraction using either ML plots or FN plots. In technological FE studies, current–voltage characteristics are often converted into other forms. Thus, measured voltage may be converted to (apparent) macroscopic field, and/or current values may be converted to macroscopic current densities. Thus, four data-input forms can be found in the context of analysing FE current–voltage results. It is also the case that over-simplified models of measurement-system behaviour are very widely assumed, and the question of whether simple use of a data-analysis plot is a valid data-interpretation procedure for the particular system under investigation has often been neglected. Past published studies on field emitter materials development appear to contain a high incidence of spurious values for the emitter characterization parameter “characteristic field enhancement factor”. A procedure (the so-called “Orthodoxy Test”) was described in 2013 that allows a validity check on measurement-system behaviour, and found that around 40% of a

This research aims to obtain a more in-depth understanding of the field emission properties of tungsten single-tip field emitters (STFEs) coated with a several tens of nanometer thin barrier of Al2O3. The introduction of an additional barrier into the metal-vacuum interface system of the emitter can be beneficial to improve its performance. The tungsten emitters were prepared using a two-step electrochemical drop-off etching technique. Thin oxide barrier coatings were prepared by using low-temperature atomic layer deposition (ALD), a chemical vapor deposition technique. Field emission was studied in an internally developed field emission microscope (FEM) working in UHV vacuum (< 1·10−7 Pa), and the experimental field emission data were analyzed by the so-called Murphy-Good plotsThe value of the local work function of the grown oxide layer were investigated using Ultra-violet photoelectron spectroscopy (UPS).

This paper focuses on the research and development of a suitable method for creating a selective emitter for the visible and near-infrared region to be able to work optimally together with silicon photovoltaic cells in a thermophotovoltaic system. The aim was to develop a new method to create very fine structures beyond the conventional standard (nanostructures), which will increase the emissivity of the base material for it to match the needs of a selective emitter for the VIS and NIR region. Available methods were used to create the nanostructures, from which we eliminated all unsuitable methods; for the selected method, we established the optimal procedure and parameters for their creation. The development of the emitter nanostructures included the necessary substrate pretreatments, where great emphasis was placed on material purity and surface roughness. Tungsten was purposely chosen as the main material for the formation of the nanostructures; we verified the effect of the formed structure on the resulting emissivity. This work presents a new method for the formation of nanostructures, which are not commonly formed in such fineness; by this, it opens the way to new possibilities for achieving the desired selectivity of the thermophotovoltaic emitter.

Modern material science often makes use of polyvinylidene fluoride thin films because of various properties, like a high thermal and chemical stability, or a ferroelectric, pyroelectric and piezoelectric activity. Fibers of this polymer material are, on the other hand, much less explored due to various issues presented by the fibrous form. By introducing carbon nanotubes via electrospinning, it is possible to affect the chemical and electrical properties of the resulting composite. In the case of this paper, the focus was on the further improvement of interesting polyvinylidene fluoride properties by incorporating carbon nanotubes, such as changing the concentration of crystalline phases and the resulting increase of the dielectric constant and conductivity. These changes in properties have been explored by several methods that focused on a structural, chemical and electrical point of view. The resulting obtained data have been documented to create a basis for further research and to increase the overall understanding of the properties and usability of polyvinylidene fluoride fiber composites.

The method of inclusion of various additives into a polymer depends highly on the material in question and the desired effect. In the case of this paper, nitride salts were introduced into polyvinylidene fluoride fibers prepared by electrospinning. The resulting changes in the structural, chemical and electrical properties of the samples were observed and compared using SEM-EDX, DSC, XPS, FTIR, Raman spectroscopy and electrical measurements. The observed results displayed a grouping of parameters by electronegativity and possibly the molecular mass of the additive salts. We virtually demonstrated elimination of the presence of the -phase by addition of Mg(NO3)2, Ca(NO3)2, and Zn(NO3)2 salts. The trend of electrical properties to follow the electronegativity of the nitrate salt cation is demonstrated. The performed measurements of nitrate salt inclusions into PVDF offer a new insight into effects of previously unstudied structures of PVDF composites, opening new potential possibilities of crystalline phase control of the composite and use in further research and component design.

BiFeO3 (BFO) films on highly oriented pyrolytic graphite (HOPG) substrate were obtained by the atomic layer deposition (ALD) method. The oxidation of HOPG leads to the formation of bubble regions creating defective regions with active centers. Chemisorption occurs at these active sites in ALD. Additionally, carbon interacts with ozone and releases carbon oxides (CO, CO2). Further annealing during the in situ XPS process up to a temperature of 923 K showed a redox reaction and the formation of oxygen vacancies (Vo) in the BFO crystal lattice. Bubble delamination creates flakes of BiFeO3-x/rGO heterostructures. Magnetic measurements (M–H) showed ferromagnetism (FM) at room temperature Ms ~ 120 emu/cm3. The contribution to magnetization is influenced by the factor of charge redistribution on Vo causing the distortion of the lattice as well as by the superstructure formed at the boundary of two phases, which causes strong hybridization due to the superexchange interaction of the BFO film with the FM sublattice of the interface region. The development of a method for obtaining multiferroic structures with high FM values (at room temperature) is promising for magnetically controlled applications.

The paper describes the development and production of a nano-optical device consisting of a nano-perforated layer of silicon nitride stretched in a single-crystal silicon frame using electron beam lithography (EBL) and reactive ion etching (RIE) techniques. Procedures for transferring nanostructures to the nitride layer are described, starting with the preparation of a metallic mask layer by physical vapor deposition (PVD), high-resolution pattern recording technique using EBL and the transfer of the motif into the functional layer using the RIE technique. Theoretical aspects are summarized including technological issues, achieved results and application potential of patterned silicon nitride membranes.

Polyvinylidene fluoride (PVDF) is a modern polymer material used in a wide variety of ways. Thanks to its excellent resistance to chemical or thermal degradation and low reactivity, it finds use in biology, chemistry, and electronics as well. By enriching the polymer with an easily accessible and cheap variant of graphite, it is possible to affect the ratio of crystalline phases. A correlation between the ratios of crystalline phases and different properties, like dielectric constant as well as piezo- and triboelectric properties, has been found, but the relationship between them is highly complex. These changes have been observed by a number of methods from structural, chemical and electrical points of view. Results of these methods have been documented to create a basis for further research and experimentation on the usability of this combined material in more complex structures and devices.

This paper investigates field emission behavior from the surface of a tip that was prepared from polymer graphite nanocomposites subjected to electrochemical etching. The essence of the tip preparation is to create a membrane of etchant over an electrode metal ring. The graphite rod acts here as an anode and immerses into the membrane filled with alkali etchant. After the etching process, the tip is cleaned and analyzed by Raman spectroscopy, investigating the chemical composition of the tip. The topography information is obtained using the Scanning Electron Microscopy and by Field Emission Microscopy. The evaluation and characterization of field emission behavior is performed at ultra-high vacuum conditions using the Field Emission Microscopy where both the field electron emission pattern projected on the screen and current–voltage characteristics are recorded. The latter is an essential tool that is used both for the imaging of the tip surfaces by electrons that are emitted toward the screen, as well as a tool for measuring current–voltage characteristics that are the input to test field emission orthodoxy.

The objective of this work is to study the delamination of bismuth ferrite prepared by atomic layer deposition on highly oriented pyrolytic graphite (HOPG) substrate. The samples’ structures and compositions are provided by XPS, secondary ion mass spectrometry (SIMS) and Raman spectroscopy. The resulting films demonstrate buckling and delamination from the substrates. The composition inside the resulting bubbles is in a gaseous state. It contains the reaction products captured on the surface during the deposition of the film. The topography of Bi-Fe-O thin films was studied in vacuum and under atmospheric conditions using simultaneous SEM and atomic force microscopy (AFM). Besides complementary advanced imaging, a correlative SEM-AFM analysis provides the possibility of testing the mechanical properties by using a variation of pressure. In this work, the possibility of studying the surface tension of the thin films using a joint SEM-AFM analysis is shown., Cílem této práce je studium delaminace feritu bizmutu připraveného nanesením atomových vrstev na substrát vysoce orientovaného pyrolytického grafitu (HOPG).

This paper presents polymer graphite (PG) as a novel material for the scanning tunneling microscopy (STM) probe. Conductive PG is a relatively modern nanocomposite material used for micro-pencil rells containing a polymer-based binding agent and graphite akes. Its high conductivity and immunity against surface contamination, with a low price, make it seem like a highlysuitablematerialforelectrodemanufacturingingeneral. Forthetipproduction,threemethods were developed and are further described in the paper. For the production, three commercially available polymer graphite rods were used. Each has been discussed in terms of performance within the tunneling microscope and within other potential applications.

Katody obsahující pole emitorů s vysokým poměrem stran budí velký zájem jako elektronové zdroje pro vakuová zařízení. Ve snaze maximalizovat proud a proudovou hustotu byly navrženy hustší pole emitorů. To však vedlo k nežádoucím účinkům, jako je stínění pole, způsobené přítomností okolních emitorů v poli. Pro snížení efektu stínění, a tím pádem zvýšení proudové hustoty, bylo navrženo pole emitorů s uspořádáním inspirovaným přírodním principem fylotaxe. Takto navržená struktura mikropilířů byla vytvořena pomocí elektronové litografie a reaktivního iontového leptání. K vytvoření ultra ostrých hrotů s poloměrem v řádu desítek nanometrů na vrcholu každého mikropilíře byla použita technika leptání black siliconu. Analýza topografie vzorku byla provedena pomocí rastrovacího elektronového mikroskopu. Pro stanovení výstupní práce byla použita ultrafialová fotoelektronová spektroskopie. Pro zjištění emisních vlastností vyrobených struktur byl zkonstruován emisní mikroskop, jehož elektronové dělo bylo upraveno tak, aby vyrobená struktura sloužila jako katoda. Graf Murphy-Good byl použit k analýze dat o emisních vlastnostech, na které byl aplikován ortodoxní test pro kontrolu validity. Pro sledování fluktuací proudu bylo provedeno měření stability., Cathodes containing arrays of high aspect ratio field emitters are of great interest as sources of electron beams for vacuum electronic devices. The desire to maximize current and current density leads to the design of denser arrays. However, denser arrays lead to undesirable field shielding effects caused by the presence of surrounding emitters in the array. To reduce the shielding effect and thus maximize the field enhancement, an array of emitters was designed with an arrangement inspired by the natural phenomenon of phyllotaxis. The structure thus designed was created using electron beam lithography and reactive ion etching to form micropillars. A black silicon etching technique was used to create ultra-sharp tips with a radius in the order of tens of nanometers on the top of each micropillar. Analysis of the sample topography was performed by Scanning electron microscopy. Ultraviolet photoelectron spectroscopy was used to determine the work function. To find out the emission properties of the fabricated structures, a Field emission microscope was constructed and its electron gun was modified to experimentally use the fabricated structure as the cathode. A Murphy-Good plot was used to analyze the field emission data, to which the orthodoxy test was applied to check the validity of the experimental I-V data. Current stability measurement was performed to observe current fluctuations.

Téma diplomové práce je zaměřeno na metodiku charakterizace autoemisního zdroje pro elektronový mikroskop. Použitá metoda – Fowlerova-Nordheimova analýza je založená na přítomnosti kvantového tunelování, ke kterému dochází v průběhu autoemise elektronů. Práce je obsahově dělena na teoretický úvod do problematiky a praktickou část. Teoretický úvod popisuje emisi elektronů, kvantové tunelování a vlastnosti emisních zdrojů. Druhá část diplomové práce se věnuje experimentální analýze autoemisní katody. Součástí analýzy je výpočet základních charakteristik této katody. Vypočtené hodnoty stanovují celkovou kvalitu elektronové emise a zároveň poskytují informace o aktuálním stavu autoemisní katody. Výsledky F-N analýzy jsou poté srovnány s výsledky počítačové simulace autoemise elektronů. Simulace je provedena v programu COMSOL Multiphysics, který k výpočtu používá metodu konečných prvků a je nástrojem pro hodnocení významu a přesnosti Fowlerovy-Nordheimovy analýzy., The master’s thesis deals with the characterization method of the electron emitter for an electron microscope – Fowler-Nordheim analysis. The method is based on the presence of quantum tunnelling, which occurs during the field emission of electrons. The work contains the theoretical background to the topic, as well as the practical part. The theoretical introduction describes the electron emission, quantum tunnelling phenomenon and the parameters of the electron emitters. In the second part, the thesis focuses on the experimental study of the field-emission cathode. The essential characteristics of the emitter are computed. These characteristics determine the overall quality of electron emission, as well as provide information about the actual condition of the emitter. The results of the F-N analysis are subsequently compared with the results of the computer simulation of the field-emission. The simulation is performed in COMSOL Multiphysics software using the finite element method (FEM) and enables to assess the relevance and accuracy of the F-N analysis.

Téma doktorské práce se zabývá přípravou a popisem katod na bázi autoemise, jenž představují kvalitní a levný elektronový zdroj pro zařízení pracující s fokusovaným elektronovým svazkem. Pro přípravu kompozitní autoemisní katody byla využita elektrochemická metoda výroby. Kompozitní struktura katody zlepšuje proudovou stabilitu ve srovnání s čistě autoemisními katodami na bázi wolframu. Na základě charakterizace katody, jenž byla nově provedena metodou šumové spektroskopie, byla implementována technologická zlepšení stávající výroby. Metoda šumové spektroskopie je založena na analýze emisního proudu v časové a kmitočtové rovině, ale především poskytuje informace o nosiči náboje, o jeho pohyblivosti a dále o životnosti katody. Výsledky experimentální části byly rozšířeny teoretickými simulacemi, vedoucími k návrhu metodiky charakterizace vylepšené autoemisní katody., This PhD thesis describes, and covers the preparation of field-emission cathodes that represent a high-quality, inexpensive source of electrons for devices that work with a focused electron beam. In this work, an improved method of electrochemical fabrication is used for the preparation of a composite field-emission cathode. The composite structure improves current stability in comparison to tungsten-based pure field-emission cathodes. Improvements to the technology used were implemented on the basis of findings obtained using spectrum noise diagnostics, which are based on measuring and evaluating the emission current in the time and in frequency domains. Additionally, noise spectroscopy provides important information about charge transport, electron mobility, and lifespan, which is essential for future research. Results obtained using the experimental method have been further supplemented with theoretical data provided by a computer simulation in order to establish characterization procedures for improved field-emission cathodes.

Katody obsahující pole emitorů s vysokým poměrem stran budí velký zájem jako elektronové zdroje pro vakuová zařízení. Ve snaze maximalizovat proud a proudovou hustotu byly navrženy hustší pole emitorů. To však vedlo k nežádoucím účinkům, jako je stínění pole, způsobené přítomností okolních emitorů v poli. Pro snížení efektu stínění, a tím pádem zvýšení proudové hustoty, bylo navrženo pole emitorů s uspořádáním inspirovaným přírodním principem fylotaxe. Takto navržená struktura mikropilířů byla vytvořena pomocí elektronové litografie a reaktivního iontového leptání. K vytvoření ultra ostrých hrotů s poloměrem v řádu desítek nanometrů na vrcholu každého mikropilíře byla použita technika leptání black siliconu. Analýza topografie vzorku byla provedena pomocí rastrovacího elektronového mikroskopu. Pro stanovení výstupní práce byla použita ultrafialová fotoelektronová spektroskopie. Pro zjištění emisních vlastností vyrobených struktur byl zkonstruován emisní mikroskop, jehož elektronové dělo bylo upraveno tak, aby vyrobená struktura sloužila jako katoda. Graf Murphy-Good byl použit k analýze dat o emisních vlastnostech, na které byl aplikován ortodoxní test pro kontrolu validity. Pro sledování fluktuací proudu bylo provedeno měření stability., Cathodes containing arrays of high aspect ratio field emitters are of great interest as sources of electron beams for vacuum electronic devices. The desire to maximize current and current density leads to the design of denser arrays. However, denser arrays lead to undesirable field shielding effects caused by the presence of surrounding emitters in the array. To reduce the shielding effect and thus maximize the field enhancement, an array of emitters was designed with an arrangement inspired by the natural phenomenon of phyllotaxis. The structure thus designed was created using electron beam lithography and reactive ion etching to form micropillars. A black silicon etching technique was used to create ultra-sharp tips with a radius in the order of tens of nanometers on the top of each micropillar. Analysis of the sample topography was performed by Scanning electron microscopy. Ultraviolet photoelectron spectroscopy was used to determine the work function. To find out the emission properties of the fabricated structures, a Field emission microscope was constructed and its electron gun was modified to experimentally use the fabricated structure as the cathode. A Murphy-Good plot was used to analyze the field emission data, to which the orthodoxy test was applied to check the validity of the experimental I-V data. Current stability measurement was performed to observe current fluctuations.

Práce se zabývá fyzikálními vlastnostmi pyroelektrických senzorů a jejich praktickým využitím. Součástí práce je návrh a realizace měřící aparatury, jež bude využita k měření fyzikálních vlastností senzorů. Pro měření signálů pyroelektrického senzoru bude navržen nízkošumový zesilovač. Součástí práce je také návrh a realizace algoritmu pro lokalizaci infračerveného zdroje záření (plamene) v prostoru, na základě vyhodnoceného analogového signálu., The thesis analyzes the physical properties of the pyroelectric sensors and its practical use. Essential part of the work is the design and realization of the measuring set-up, which is used for the measurements of the sensors physical properties. With this workbench, main parameters of the pyroelectric sensors have been obtained. The second part of the work deals with a low noise preamplifier designing. This device was designed for the pyroelectric sensor signal measurements. The amplifier is designed to be used for a low noise, wide band measuring. During the process of amplifier designing, all the noise components have been investigated separately, using operational amplifiers models. The objective of the last part of this work is to develop the system, which would be able to localize an infrared (IR) emitting source located somewhere in the space between the installed pyroelectric sensors. For this purpose, classical localization methods could be used as well as the artificial neural networks (ANN), which are becoming still more popular these days. The system is able to detect the exact placement of the IR radiation source.

Při ovrstvování substrátu tenkou vrstvou polymerního rezistu dochází k defektům, které mohou poškodit celou, někdy i několikadenní expozici pomocí svazku elektronů - elektronovou litografií. Kvalita nanesené vrstvy, která je potřebná k následnému deponování, je velmi důležitá z hlediska následné funkčnosti vyráběné nanostrukutry. Předběžnou kontrolu kvality naneseného resistu je možné dělat ručně pomocí světelného mikroskopu. V rámci této bakalářské práce vznikl prototyp zařízení, které tyto defekty dokáže detekovat automaticky. Přesněji jde o rastrovací zařízení pojmenované WaferScan, umožňující skenovat křemíkovou podložku (wafer) optickou kamerou a analýzou obrazu v počítači zjistit polohu a velikost defektů a prachových částic v rezistu naneseném na waferu. Celé zařízení se skládá ze dvou pohyblivých os x a y, které umožňují pohyb kamery, a příslušené elektroniky. Součástí je také software k ovládání zařízení a zpracování obrazu., During the coating the substrate with a thin layer of polymer resist several defects can to occur which could damage an exposure by electron beam lithography. The quality of the resist-coated surface prior to the exposure is also very important in terms of the final functionality of the fabricated micro device. The quality of the resist-coated surface can be measured by means of human visual inspection with a visible-light microscope. This bachelor's thesis is focused on the design and assembly of the automated set-up to do this inspection automatically. More precisely, the designed set-up is called WaferScan and it allows to scan a silicon wafer coated with a resist layer. The wafer surface is scanned with an optical camera and the taken images are analyzed using computer to determine the location and the size of the defects and the dust particles in the resist layer. The entire device consists of two moving axes, x and y, (that allow the movement of the camera) and a control electronic circuitry. Software to control the scanning device and the image processing tool were also developed.

Práce se zabývá fyzikálními vlastnostmi pyroelektrických senzorů a jejich praktickým využitím. Součástí práce je návrh a realizace měřící aparatury, jež bude využita k měření fyzikálních vlastností senzorů. Pro měření signálů pyroelektrického senzoru bude navržen nízkošumový zesilovač. Součástí práce je také návrh a realizace algoritmu pro lokalizaci infračerveného zdroje záření (plamene) v prostoru, na základě vyhodnoceného analogového signálu., The thesis analyzes the physical properties of the pyroelectric sensors and its practical use. Essential part of the work is the design and realization of the measuring set-up, which is used for the measurements of the sensors physical properties. With this workbench, main parameters of the pyroelectric sensors have been obtained. The second part of the work deals with a low noise preamplifier designing. This device was designed for the pyroelectric sensor signal measurements. The amplifier is designed to be used for a low noise, wide band measuring. During the process of amplifier designing, all the noise components have been investigated separately, using operational amplifiers models. The objective of the last part of this work is to develop the system, which would be able to localize an infrared (IR) emitting source located somewhere in the space between the installed pyroelectric sensors. For this purpose, classical localization methods could be used as well as the artificial neural networks (ANN), which are becoming still more popular these days. The system is able to detect the exact placement of the IR radiation source.

Téma doktorské práce se zabývá přípravou a popisem katod na bázi autoemise, jenž představují kvalitní a levný elektronový zdroj pro zařízení pracující s fokusovaným elektronovým svazkem. Pro přípravu kompozitní autoemisní katody byla využita elektrochemická metoda výroby. Kompozitní struktura katody zlepšuje proudovou stabilitu ve srovnání s čistě autoemisními katodami na bázi wolframu. Na základě charakterizace katody, jenž byla nově provedena metodou šumové spektroskopie, byla implementována technologická zlepšení stávající výroby. Metoda šumové spektroskopie je založena na analýze emisního proudu v časové a kmitočtové rovině, ale především poskytuje informace o nosiči náboje, o jeho pohyblivosti a dále o životnosti katody. Výsledky experimentální části byly rozšířeny teoretickými simulacemi, vedoucími k návrhu metodiky charakterizace vylepšené autoemisní katody., This PhD thesis describes, and covers the preparation of field-emission cathodes that represent a high-quality, inexpensive source of electrons for devices that work with a focused electron beam. In this work, an improved method of electrochemical fabrication is used for the preparation of a composite field-emission cathode. The composite structure improves current stability in comparison to tungsten-based pure field-emission cathodes. Improvements to the technology used were implemented on the basis of findings obtained using spectrum noise diagnostics, which are based on measuring and evaluating the emission current in the time and in frequency domains. Additionally, noise spectroscopy provides important information about charge transport, electron mobility, and lifespan, which is essential for future research. Results obtained using the experimental method have been further supplemented with theoretical data provided by a computer simulation in order to establish characterization procedures for improved field-emission cathodes.