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Influence of external fields on electric field and photocurrent in CdTe detectors
Rejhon, Martin ; Franc, Jan (advisor)
This thesis is focused on a study of CdTe and CdZnTe semiconductor detectors working under high flux of radiation. We studied experimentally an influence of high flux of X-rays and optical radiation on polarization of the detector. The polarization phenomenon decreases the efficiency of the detector due to a screening of an applied electric field by a space charge accumulated at deep levels due to a trapping of photogenerated carriers. In order to measure the electric field profiles in the detectors we employed a method based on cross polarizers technique and Pockels effect. The main objective of this work was to study the possibilities of an optical de-polarization of CdTe and CdZnTe detectors for different photon energies of additional light, its dynamics and physical origin. We have found that detectors can be de-polarized by above bandgap light. Moreover, CdZnTe detector can be depolarized by near infrared light and in a pulse mode. The de- polarization is associated with a compensation of the space charge at deep traps.
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Surface modification of glass fibers using plasma nanotechnology
Sedlák, Filip ; Knob, Antonín (referee) ; Čech, Vladimír (advisor)
Diploma thesis is aimed at deposition of thin films on glass fibers using plasma-enhanced chemical vapor deposition from tetravinylsilane as a monomer. Such surface modified glass fibers were used as reinforcements for fabrication of polymer composites with unsaturated polyester resin as a matrix. Chemical and optical properties of prepared thin films were characterized using infared spectroscopy and spectroscopic ellipsometry. An influence of deposited thin films on the shear strength of composite material was observed using short-beam shear test.
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Sensoric Properties of Organic Materials
Tmejová, Kateřina ; Zmeškal, Oldřich (referee) ; Kratochvílová, Irena (referee) ; Nešpůrek, Stanislav (advisor)
The first part of the work is aimed to the study of changes of electrical properties of substituted phthalocyanines under the influence of humidity. Thin films were prepared by spin coating technique. During the influenece of humidity electrical conductivity increases. Sorption and desorption and the changes in electrical properties under the repated humidity exposure were investigated as well. Impedance spectroscopy was used for the studies. The second part of this work consists of optical studies and changes of optical parametrsunder the influence of different alcohols (methanol, ethanol, 2-propanol) exposures. The investigated samples were prepared by vacuum evaporation a glow-discharge-induced sublimation. The changes of optical reflectances of the films upon exposure to alcoholvapour-containg atmospheres were studied as a function of alcohol concetration and exposure time.
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Two-photon photopolymerization with multiple laser beams
Skalický, Jiří ; Pilát,, Zdeněk (referee) ; Jákl,, Petr (advisor)
Photopolymerization is a technique used to create surface structures or microobjects from a photoresist. This process is started by illuminating the sample with a light of proper wavelength absorbed by the resist. After exposure, the sample is processed according to the type of the photoresist – be it heating, treating with developer or just washing the unaffected monomer with some reagent. Focused femtosecond laser beam with double wavelength can be used in the process. Short pulse length with high photon density starts two-photon absorption localized in the vicinity of focal point. The method resolution is thus increased and details with 1/10 micrometer size can be created. Moreover, very short laser pulse decreases the heat affected zone and the risk of thermal initiation is minimized. Manufacturing of larger structures composed of tiny details with two-photon photopolymerization is time-demanding process. Therefore, we have complemented the optical setup with spatial light modulator (SLM), which splits the incoming laser beam into several beams with holograms dynamically generated by a computer. Polymerization can be thus performed by multiple foci simultaneously which can be used to create separated microparticles or periodical surface structures. Additional speed improvement of the process can be substitution of static configuration, requiring sample replacement after each exposition, with continuous setup using microfluidic channel steadily supplied with photoresist transported to the active region of the sample.
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Deposition of Indium Tin Oxide and study of its optical properties
Olivíková, Gabriela ; Kvapil, Michal (referee) ; Dvořák, Petr (advisor)
This work is focused on preparation and deposition of thin layers of indium tin oxide (ITO) by ion beam sputtering (IBS) and ion beam assisted deposition (IBAD). In the theoretical part, the electrical and optical properties, preparation methods, and applications are reviewed. In the experimental part, the optical and transport properties of deposited films are investigated by spectroscopic methods. It is shown that simultaneous bombardment of the surface with oxygen ions with energy 80 eV results in increase of transmittance in the visible range of spectrum. IBAD thus confirmed as a suitable method for modification of optical properties.
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Image processing within determination of topographic surface parameters
Boháč, Martin ; Ohlídal, Miloslav (referee) ; Šťastný, Jiří (advisor)
This work deal with determination topohraphic parameters of a randomly rough surface by the help of method of shearing interferometry. It is a optical method for determination surface roughness. The basic idea is based of on deformation interference strips which are made by interference of the same mutually translated monochrome luminous wavefronts. The wavefront is created after transit or reflection monochrome lights from the surface of a studied sample. The wavefronts creates picture with deformed interference strips , which carries information about character of the surface. This information can be profited by algorithms of image processing from the picture . The thesis was developed in research project MSM 0021630529 Intelligent Systems in Automation.
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Analysis of low-molecular proteins in barley by the SDS-PAGE method during malting
Myslivcová, Pavla ; Svoboda, Zdeněk (referee) ; Mikulíková, Renata (advisor)
This diploma thesis deals with the analysis of low molecular weight proteins in barley during malting by SDS-PAGE method. Attention was paid to PR proteins, specifically LTP proteins and thionins, considered to be connected with gushing effect. Barley samples, malt intermediates and malt samples taken in 10 consecutive days to cover the whole malting process were used for the experiment. In total, 5 samplings were used for the analysis. Proteins extracted from the samples were separated by SDS-PAGE using a Tris-tricine buffer system. The protein lines of LTP proteins and thionins were identified in the resulting gels. The relative optical density values of the selected protein bands were obtained to assess the effect of malting on these proteins. A similar pattern of change in the content of mentioned low molecular weight proteins during the malting process was observed. This was confirmed by finding a statistically significant positive correlation between the relative optical density values of LTP proteins and thionins. Furthermore, the relationship between the low molecular weight protein content and the gushing potential and the microbiological contamination of the samples was investigated, but was not confirmed.
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