Browsing by Author "Čížek, Jakub"

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    Improvement of luminescence properties of n-GaN using TEGa precursor
    (ELSEVIER, RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2020-01-01) Hubáček, Tomáš; Hospodková, Alice; Kuldová, Karla; Slavická Zíková, Markéta; Pangrác, Jiří; Čížek, Jakub; Liedke, Maciej Oskar; Butterling, Maik; Wagner, Andreas; Hubík, Pavel; Hulicius, Eduard
    The aim of this work is to compare and improve optical and structural properties of GaN layers prepared using TMGa or TEGa precursors. MOVPE grown GaN buffer layers on sapphire substrates are usually grown from TMGa precursor at the temperatures above 1000 degrees C. These layers contain deep and shallow acceptor levels which are responsible for blue and yellow defect bands in luminescent spectra. Both defect bands are detrimental for all major nitride device applications. Especially n-doped GaN layers suffer from strong yellow defect bands. In this work, it is shown that yellow band photoluminescence intensity can be suppressed by using TEGa precursor during the growth of n-doped GaN layers. Different kinds of growth parameters, such as growth temperature or growth rate, have been studied. It is also shown that the change of carrier gas (H-2 or N-2) has very strong influence on the layer quality. H-2 carrier gas increased intensity of yellow band in sample grown from TEGa precursor while N-2 carrier gas had the same effect for sample grown from TMGa precursor. Variable energy positron annihilation spectroscopy showed creation of single V-Ga in H-2 atmosphere and clustering of V-Ga to big complexes ((V-Ga)(3)(V-N)(n)) in N-2 atmosphere.
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    Jižní terasy v Hradci Králové
    (2009-01-01) Čížek, Jakub
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    Jižní terasy v Hradci Králové
    (Technická Univerzita v Liberci, 2013-12-20) Čížek, Jakub; Suchomel, Jiří
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    Pruitt Igoe Now
    (2012-01-01) Čížek, Jakub
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    Pruitt Igoe Now
    (Technická Univerzita v Liberci, 2012-01-01) Čížek, Jakub; Suchomel, Jiří
    Area of my project is placed in St. Louis in USA. Area is former project for poor inhabitants from year 1950. Project had many problems, which escalate in 1972, when first building was destroyed. From that year the territory is vacant. The goal is regeneration with creation of new program. My proposal contains park, where I use concept of congestion of surfaces and footprint of former paths. The park contains many diverse functional places, where no place is not unemployed. Whole area is designed like free-time space with artist?s production. My effort is to find new qualities in this unemployment area, but also for neigbourghood. This qualities can bring the artists and young people. Main buildings of project are artist?s incubator and agora. Incubator is determinated for artist?s work, but also for presentation of theirs work. Agora is for local residents, for various activities. On the edges of area is housing for artist, students or young families.