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Defects limiting charge collection in semiinsulated CdZnTe
Zajac, Vít ; Franc, Jan (advisor) ; Šikula, Josef (referee)
Title: Defects limiting charge collection in semiinsulated CdZnTe Author: Vít Zajac Department: Institute of Physics of Charles University Supervisor: doc. Ing. Jan Franc, DrSc., Institute of Physics of Charles University Abstract: We achieved to detect photoluminescence transitions deep in the band gap in 4 samples cut from 2 different crystals of semiinsulating Cd1-xZnxTe (x = 0,02 - 0,18) in a row of points along the growth axis. The spectral peaks give evidence of the presence of deep levels in the sample and the intensity of the photoluminescence peaks is to a certain extent proportional to the concentration of these levels. A comparison between resistivity and photoconductivity that were measured by a contact-less method showed that the change of photoluminescence intensity of deep levels does not bring about an unambigous change of neither resistivity nor photoconductivity. Correlation analysis of resistivity and photoconductivity of 6 samples from 4 different crystals confirmed the following model: A shift of the Fermi level within the band gap induced by a change of donor-acceptor compensation is accompanied by an unambigous change of resistivity and results in a change in occupation of the deep levels. This causes a change in the photoconductivity of the crystal because the occupation factor of...
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Non-metallic resistive low temperature thermometers
Duda, Daniel ; Rotter, Miloš (advisor) ; Janů, Zdeněk (referee)
temperature calibration has been carried out on series of resistors made of RuO2 of SMD type in the bath of normal and superfluid helium in temperatures at 1.4 - 4.2 K with reference thermometer of saturated vapor pressure. Measured temperature dependence of electrical resistance of resistors was analyzed using the exponential function and Chebychev's polynomials. It was established an optimum calibration for the use of resistors as thermometers.
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Methodology of Determination of Electroinsulating Properties
Čanigová, Veronika ; Nevřivová, Lenka (referee) ; Sokolář, Radomír (advisor)
The core of this bachelor thesis is porcelain and electrical porcelain property specification accompanied by definition and explanation of electric conductivity. The theoretical section provides insight into electrical porcelain production from initial raw material exploitation to final stages of body baking. The experimental part compiles a number of electrical porcelain test methods based on current European standards and draft test procedures, which are followed in order to specify properties of conventional electrical porcelain as well as emerging anorthite porcelain based on aluminate cement.
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Electrical properties analysis of epoxy resins with various fillers
Horák, Luděk ; Kazelle, Jiří (referee) ; Frk, Martin (advisor)
Presented bachelor thesis is focused on studying electroinsulating epoxy resin-based sealings. It describes the chemical composition, production, properties and measuring methods of basic electric quantities of these materials. This work also embodies a preparation of composite epoxy resin samples with different kinds of micro-ground siliceous sand as a filling. The samples given are measured on the temperature dependency of relative permitivity, dissipation factor and inner resistivity.
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Inorganic fillers effect on electrical properties of the epoxy resins
Doležel, Tomáš ; Jirák, Josef (referee) ; Frk, Martin (advisor)
This thesis deals with problems of electrical insulation materials based on epoxy composites used in the electronics industry. This thesis is divided into theoretical part focused on composite materials, their technological processing and diagnostics. It also describes dielectric materials, their properties and events taking place in their structure. The experimental section describes the measurement of electrical properties of samples of electrical insulating materials with different types of fillers.
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Degradation of nanocomposites
Polách, Ondřej ; Rozsívalová, Zdenka (referee) ; Polsterová, Helena (advisor)
The present work deals with the electrical properties of nanocomposite materials. Samples for the practical part consisting of epoxy resin as matrix and SiO2 as nanofillers and were made in four different percentage performance. There is investigated the influence of thermal degradation of nanocomposite materials change resistivity, loss factor and relative permitivity.
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Lead Free Solder Joint - Models for Reliability Prediction
Nestrojil, Michal ; Šandera, Josef (referee) ; Starý, Jiří (advisor)
This bachelor's thesis deals with reliability prediction of lead-free solder joint. Background research of fatigue models for lead free solder joint.is described in theoretic part Basic terminology and lead free soldering technology operations are mentioned in the theoretical part too. The practical part is dealing with observation of resistivity and solder joint strength during thermal cycling. Evaluation of results and experiments and posibility for future application of these results for fatigue model realisation is discussed in the end of this bachelor's thesis
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