Дисертації з теми "Structures en V"
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1
Larkin, Victoria. "Transport studies in GaAs/AIGaAs V-groove quantum wires." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269463.
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2
Grimes, Richard Thomas. "Far infrared studies of III-V semiconductors structures." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238193.
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3
Tabata, Americo Sheitiro. "Caractérisation optique de micro-structures III-V contraintes." Lyon, INSA, 1994. http://www.theses.fr/1994ISAL0003.
Повний текст джерелаАнотація:
Ce travail a été réalisé dans le cadre d'un projet européen "ESPRIT Basic Research" intitulé "Structure of low dimensionality for future quantum semiconductor devices" - contrat n° 3086. L'objectif principal a été d'étudier les étapes d'élaboration du dispositif de type HEMT dans la filière InP, en utilisant les effets physiques de la contrainte sur la structure de bande et sur la masse effective pour obtenir des dispositifs à très haute mobilité. L'objectif de ce travail de thèse a été d'effectuer des études physiques de base, par photoluminescence sur des structures contraintes du type InP/InGaAs/InP, InAlAs/InGaAs/InP et InGaAs/ AlGaAs/GaAs. Dans ce cadre nous sommes intéressés particulièrement aux propriétés optiques des couches contraintes, à l'analyse de certaines propriétés structurelles telles que la rugosité d'interface et l'épaisseur critique pour la relaxation des couches contraintes, ainsi qu'à l'analyse des effets de contraintes sur la structure de bandeThis work has been done in the framework of the European project "ESPRIT Basic Research" entitled "Structure of low dimensionality for future quantum semiconductor devices". The purpose of this contract was to study the elaboration of strained HEMT (High electron mobility transistors) devices on the basis of the InP technology. In this thesis, we have studied optical properties of strained InGaAs/lnP, InGaAs/InAlAs/lnP and InGaAs/AlGaAs/GaAs systems. Some structural properties like interface roughness and the critical thickness for relaxation were also analysed, as well as, the strain effect on the band structure. By low temperature photoluminescence measurements we have studied: 1) stabilisation process of InP substrate; 2) optical properties of InAs/lnP surface quantum wells; 3) optical properties of InAs/lnP quantum wells; 4) strain relaxation on the strained InGaAs/lnP system; 5) interfacial PL emission from the strained InGaAs/lnP interface; 6) optical and structural properties of Ino. S3Gao. 47As/lnxGa1-xAs (x=0. 65, 0. 75, 0. 82) system as a fonction of growth conditions; 7) transitivity rule on the Ino. S3Gao. 74As/lnxGa1-xAs (x=0. 65, 0. 75, 0. 82) system; 8) optical and structural properties of lnxGa1-xAs/lnAlAs/InP lattice matched (x=0. 53) and strained (x=0. 60) single quantum wells; 9) many body effects on the InGaAs/lnAlAs system; 10) optical characterisation of InGaAs/lnAlAs/lnP lattice matched and strained HEMT structures; 11) optical characterisation of InGaAs/AlGaAs/GaAs HEMT structures and 12) optical characterisation of (InAs)(GaAs)/AlGaAs/GaAs HEMT structures
4
Coles, Rikki J. "Quantum optical circuits using III-V nanophotonic structures." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/9624/.
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5
Falešník, Vlastimil. "Podélné struktůry v optických vláknech s využitím v senzorice." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-220417.
Повний текст джерелаАнотація:
This semestral work describes key concepts, principles and basic characteristics of optical fibers. Furthermore, the principles of phase mask and subsequent records of perpendicular or tilted structures in fiber are being discussed. The work also introduces the use of such structures in sensorics as well as its connection to Bragg grating. Considerable part of this thesis is dedicated to analysis and production of longitudinal structures in fibers.
6
Steer, Matthew John. "Optical and structural characterisation of III-V semiconductor qauntum wire and quantum dot structures." Thesis, University of Sheffield, 1998. http://etheses.whiterose.ac.uk/3458/.
Повний текст джерелаАнотація:
This thesis describes an extensive study of the optical and structural properties of GaAs/AlGaAs V-groove quantum wire and InAs/GaAs self-organised quantum dot structures. For the optical characterisation, the spectroscopic techniques of photoluminescence (PL), photoluminescence excitation (PLE), cathodoluminescence (CL) and electroluminescence (EL) have been used. In addition important information concerning the structural properties of the quantum wires and quantum dots has been obtained by high resolution transmission electron microscopy (TEM) measurements. Initial characterisation and optimisation of the quantum wire structures was conducted using CL and TEM imaging. Further optical characterisation of optimised structures was performed using a micro-focusing PL set-up which produced a laser spot size of -'2µm, allowing individual wires to be studied. Excitation under both high and low power density conditions revealed important information concerning the quality of the growth and the nature of the one-dimensional` confinement within the structure. Structures were grown with the quantum wires placed in the intrinsic region of a p-i-n junction. EL spectroscopy measurements allowed the observation of subband filling effects and an enhanced luminescence intensity for the quantum wire for low forward bias currents. This latter behaviour has important implications for device applications. An investigation of these p-i-n samples in magnetic fields up to 14T, revealed further evidence for 1D confinement in the quantum wires and 2D confinement of carriers in a vertical quantum well. This vertical quantum well, a feature that arises automatically during the growth, appears to channel carriers into the quantum wire, providing a possible mechanism for the enhanced wire electroluminescence intensity observed. In addition, evidence is presented for a possible excitonic-free carrier transition which is observed for high carrier densities in the wires. TEM structural analysis of self-organised InAs/GaAs quantum dots has shown that the dots can show a high degree of surface ordering, aligning themselves on the step edges of the underlying substrate. Excitation under high laser power densities using the micro-PL set-up has shown subband separations of around 75meV, which is very promising for room temperature opto-electronic device applications. In addition, very narrow line width emission has been observed from individual quantum dots on a small sub-micron etched mesa which contains -100 dots. The electronic structure of the quantum dots has been probed using resonant PL and PLE. These techniques have revealed important information regarding carrier relaxation mechanisms that exist in the quantum dots. In PLE features are observed at approximately 60 and 90meV from the detection energy and which move rigidly in energy when the detection energy is varied. This behaviour is attributed to carrier relaxation by the emission of multiple LO- phonons, a process that appears to bypass any `phonon bottleneck'. Similar features are also observed in resonantly excited PL spectra. Two distinct carrier relaxation mechanisms are demonstrated by this technique: a non-resonant mechanism from the upper excited state and a resonant mechanism involving the emission of multiple LO phonons, from the first excited state.
7
Leibnitz, P., G. Reck, H. J. Pietzsch, and H. Spies. "Structures of technetium and rhenium complexes." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-29787.
Повний текст джерелаАнотація:
Investigations in the 99mTc chemistry are stimulated by the search for new radiopharmaceuticals for nuclear medical applications. To understand the coordination mode of Tc with various complexing agents, macroscopic studies of technetium coordination chemistry are often performed using the low energy ß-emitting radionuclide 99Tc, which has a much longer half life (t1/2 = 2.12 x 105 years) than 99mTc, in the mg level. Investigations of Re coordination chemistry are done in conjunction with Tc studies because Re possesses chemical properties similar to those of Tc. For some chemical tasks, Re provides a non-radioactive alternative to work with Tc radioisotopes. In addition, 186Re and 188Re are of great interest to nuclear medicine as they possess nuclear properties favorable for use in therapeutic radiopharmaceuticals. Our investigations of Tc and Re coordination chemistry are toward this goal. A large series of technetium and rhenium complexes resulted from this studies have been characterized by X-ray crystal structure determinations. This survey covers the structural investigations performed by P.Leibnitz and G.Reck (BAM) from 1992 till now. It summarizes results obtained in the Rossendorf technetium group and is not intended to compete with the well-written reviews published so far.
8
Leibnitz, P., G. Reck, H. J. Pietzsch, and H. Spies. "Structures of technetium and rhenium complexes." Forschungszentrum Rossendorf, 2001. https://hzdr.qucosa.de/id/qucosa%3A21805.
Повний текст джерелаАнотація:
Investigations in the 99mTc chemistry are stimulated by the search for new radiopharmaceuticals for nuclear medical applications. To understand the coordination mode of Tc with various complexing agents, macroscopic studies of technetium coordination chemistry are often performed using the low energy ß-emitting radionuclide 99Tc, which has a much longer half life (t1/2 = 2.12 x 105 years) than 99mTc, in the mg level. Investigations of Re coordination chemistry are done in conjunction with Tc studies because Re possesses chemical properties similar to those of Tc. For some chemical tasks, Re provides a non-radioactive alternative to work with Tc radioisotopes. In addition, 186Re and 188Re are of great interest to nuclear medicine as they possess nuclear properties favorable for use in therapeutic radiopharmaceuticals. Our investigations of Tc and Re coordination chemistry are toward this goal. A large series of technetium and rhenium complexes resulted from this studies have been characterized by X-ray crystal structure determinations. This survey covers the structural investigations performed by P.Leibnitz and G.Reck (BAM) from 1992 till now. It summarizes results obtained in the Rossendorf technetium group and is not intended to compete with the well-written reviews published so far.
9
Verschoor, Geraldine Laura Ballantyne. "III-V semiconductor structures and devices of reduced dimensionality." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244624.
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10
Kameni, Boumenou Christian. "Scanning probe force microscopy of III-V semiconductor structures." Thesis, Nelson Mandela University, 2017. http://hdl.handle.net/10948/13992.
Повний текст джерелаАнотація:
In this dissertation, cross-sectional potential imaging of GaAs-based homoepitaxial, heteroepitaxial and quantum well structures, all grown by atmospheric pressure Metal-organic Vapor Phase Epitaxy (MOVPE) is investigated. Kelvin probe force microscopy (KPFM), using amplitude modulation (AM) and frequency modulation (FM) modes in air and at room temperature, is used for the potential imaging. Studies performed on n-type GaAs homoepitaxial structures have shown two different potential profiles, related to the difference in electron density between the semi-insulating (SI) substrate and the epilayers. It is shown that the contact potential difference (CPD) between the tip and sample is higher on the semi-insulating substrate side than on the n-type epilayer side. This change in CPD across the interface has been explained by means of energy band diagrams indicating the relative Fermi level positions. In addition, it has also been found that the CPD across the interface increases with electron density. This result is in qualitative agreement with theory. In addition, as known from literature, even under ambient conditions FM mode KPFM provides better lateral resolution and more realistic CPD values than AM mode KPFM. Compared to the case of AM mode analysis, where the experimental CPD values were on average of the theoretical values, the CPD values from FM mode analysis are on average of the theoretical ones. Furthermore, by using FM mode, the transition across the interface is sharper and the surface potential flattens/saturates as expected when scanning sufficiently far away from the junction. The non-neutral space charge region of the sample with an electron density of for example, is as measured by FM-KPFM, whereas for AM-KPFM, the width is even more than and the potential profiles do not saturate. For the p-type GaAs homoepitaxial structures, FM mode measurements from a sample with a dopant density of are presented. As in the case of n-type GaAs,a similar potential profile showing two main domains has been obtained. However, unlike the case of type GaAs where the potential measured on the epilayer side is higher than that on the substrate side, the potential on the epilayer side of the junction is lower in this case due to the fact that the Fermi level of p-type GaAs is below that of the substrate.
11
Weiss, Bernard Lawson. "Modelling and characterisation III-V semiconductor quantum well structures and Si based structures for optoelectronic applications." Thesis, University of Surrey, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267875.
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12
Ng, Inn-Khuan. "TEM characterisation of III-V semiconductor multiple quantum well structures." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245224.
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13
Zhou, Ruiping. "Structural And Electronic Properties of Two-Dimensional Silicene, Graphene, and Related Structures." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1341867892.
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14
Гричановська, Тетяна Михайлівна, Татьяна Михайловна Гричановская, Tetiana Mykhailivna Hrychanovska та Л. А. Шешеня. "Магніторезистивні властивості тришарових структур на основі Ni і V або Fe і V". Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/27671.
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15
Petr, Radovan. "Městské divadlo v Kuřimi." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227681.
Повний текст джерелаАнотація:
The theme of the master´s theses is to design a wooden structure of city theater with internal steel construction. The concept of wooden structure is developed in two versions according to standard ČSN EN. The theses solve the static effect of the construction and design of individual parts and materials. Theater has dimensions 49.0 x 25.6 m, max. height of 12.5 meters. The construstion is devise to withstand a weight and applicability. The supporting structure of the roof is solved using by 13 arched plate girders. The second variant is designed as arched truss girders. The gable wall is glassed-in, glass envelopes support by wooden structure with columns and side runners. The work also includes solutions for joins and construction details. The structure was solved in the program RSTAB Dlubal 8. The assessment of the components was done using additional module TIMBER Pro. First Variant of plate girder was checking by manual report. The work includes drawings.
16
Piva, Paul Garrett. "A photoluminescence study of intermixed III/V semiconductor quantum well structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq26357.pdf.
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17
Jenkins, Christian. "Cross-sectional atomic force microscopy of III-V semiconductor device structures." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55920/.
Повний текст джерелаАнотація:
Atomic force microscopy (AFM) in air has been used to study various III-V semiconductor heterostructures. Topography of the (110) cleaved cross-sections has been examined where oxidation processes modify the surface and allow the structures to be investigated. This research aims to establish the potential of this technique as a metrology tool for use in an industrial environment. AlGas/GaAs was used as the prototypical system, and a test structure grown in order to establish how differences in oxidation rates between the different material compositions may be used to establish composition and layer thickness for heterostructure devices. The dependence of oxidation rate on layer composition and thickness has been confirmed. The mechanisms of field-aided and diffusion limited growth have been determined to be responsible for the oxidation of the AlGas layers within the test structure, with field aided being the dominant mode for materials x < 0.8 and diffusion limited dominating for layers x > 0.8 observed. In addition, a new effect of interface enhanced oxide growth have been observed and quantified in terms of layer composition. It is found to be most important for Al09Gao, As layers of 50--100 nm thickness during relatively early stages of oxidation. The use of phase detection microscopy has also been applied for the first time to determine the presence of layers where no measurable step heights are present. Unlike previous reports, there has been no observed difference in oxidation rate between p- and -type materials. These findings have been applied to real device structures, where the material composition of Al/JaAs can be determined to within x 0.02 and layer widths may be determined to within 3 nm at best. It has been shown that step height differences of as little as 0.1 A are sufficient to distinguish between layers, and that quantum wells of as little as 42 A in width are detectable.
18
Bouzar, H. "Thin films and layered structures of Nb-Sn and Cu-V." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384427.
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19
Wu, Yu-shu George McGill T. C. "Electronic properties of II-VI superlattices and III-V tunnel structures /." Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-06152006-080033.
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Smith, John Stephen Yariv Amnon. "III-V molecular beam epitaxy structures for electronic and optoelectronic applications /." Diss., Pasadena, Calif. : California Institute of Technology, 1986. http://resolver.caltech.edu/CaltechETD:etd-03082008-083912.
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21
Ilavská, Adriana. "Kooperativní teorie her v lokálních konfliktech." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-399587.
Повний текст джерелаАнотація:
The Cooperative Game Theory is a scientific discipline which offers rich mathematical apparatus for describing complex situations in the social reality. Its apparatus includes an extension to hierarchical structures and therefore can be applied to numerous research problems from the International Relations field. However, a cooperative game theoretical approach is very scarcely used. The main goal of the diploma thesis is to demonstrate, on the research problem of decision making in participation in local conflicts, the benefits of results that can be achieved by the application of the Cooperative Game Theory. In the first part of the thesis, theoretical foundations are laid and basic concepts are introduced. The second part is focused on forming a series of models of cooperative games with hierarchical structures from four local conflict situations, which are subsequently restricted in order to describe authoritative relations in structure. Restricted games are solved, the results are interpreted and evaluation of how these results can contribute to addressing the research problem follows.
22
Ashmore, Adam Dennis. "Optical characterisation of III-V semiconductor quantum dots and quantum dot structures." Thesis, University of Sheffield, 2004. http://etheses.whiterose.ac.uk/3563/.
Повний текст джерелаАнотація:
This thesis describes an extensive study of the optical properties of In(Ga)As/Ga(Al)As quantum dots, both singularly and in laser devices. For the optical characterisation, the spectroscopic techniques of photoluminescence (PL), photoluminescence-excitation (PLE) and electroluminescence (EL) have been used. Additionally, for studying submicron structures, sophisticated micro-PL techniques allowed excitation, and detection, of a single quantum dot. A variety of special growth and fabrication techniques were used to isolate a single quantum dot from the rest of the ensemble. Firstly, a submicron mesa that isolated a single quantum dot was fabricated using e-beam lithography and dry etching techniques. Excitation intensity and wavelength dependence of the emission provided information about the nature of the exciton complexes in the dot and the absorption and relaxation of carriers in the structure. The linewidth of the single exciton, and the variation with temperature, was measured. Secondly, samples consisting of a single layer of InGaAs quantum dots incorporated within the intrinsic region of a GaAs/AlGaAs Metal-Insulator-Semiconductor type Schottky structure allowed sequential dot charging via variation of the gate bias. Both n- and p- type samples, grown under similar conditions, were investigated. Single quantum dots were probed through submicron apertures opened in the top metal contact using electron beam lithography and dry etching. The emission undergoes several pronounced changes as additional carriers are sequentially loaded into the dot. The results reveal direct information regarding Coulomb interaction and correlation effects in dots containing a controlled number of excess electrons (up to four) or holes (up to two). Magneto- optical results reveal further information about the few-particle wave functions. A detailed study of the device performance and physical processes in In(Ga)As- Ga(Al)As self-assembled quantum dot lasers showed that these lasers offer several potential advantages over conventional quantum well lasers including low threshold current density, temperature insensitive threshold current density and high differential gain. Device performance (threshold current density and its variation with temperature) has been studied as a function of a number of parameters, including dot density, dot composition and dot confinement potential. The application of large (<14T) magnetic fields has been used to study carrier transport and dot carrier capture effects. When applied along the growth axis, such fields result in an increase in the threshold current density and a decrease in the external quantum efficiency. These effects are attributed to inhibited inplane carrier transport resulting in an increase in the carrier capture efficiency by non-lasing dots. Spontaneously emitted light, recorded via small windows formed in the top metallic contact, has been studied as a function of injection current and temperature. Analysis of this data provides information on non-radiative loss mechanisms and dot carrier dynamics.
23
NIEBLES, FRANCISCO JUAN RACEDO. "SELECTIVE AREA EPITAXIAL GROWTH OF III-V SEMICONDUCTOR STRUCTURES FOR OPTOELECTRONIC APPLICATIONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2000. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7569@1.
Повний текст джерелаАнотація:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOA integração monolítica de um modulador com um guia de onda é de muito interesse para aplicação em comunicações ópticas pelo fato de que podemos diminuir as perdas por acoplamento óptico entre os dois dispositivos e usar moduladores curtos que operem em altas taxas de transmissão de dados. O crescimento epitaxial seletivo é uma das técnicas mais promissoras na atualidade para aplicação na integração monolítica de dispositivos semicondutores. Esta técnica permite controlar a espessura e a tensão das camadas crescidas seletivamente permitindo otimizar a integração e as características das estruturas dos dispositivos. A tese trata da implementação, do estudo e da aplicação do crescimento epitaxial seletivo por MOCVD de estruturas casadas e tensionadas de poços quânticos múltiplos de InGaAs/InAlAs para a fabricação de moduladores de amplitude baseados no efeito Stark e sua integração com guias de onda. O desempenho dos moduladores, baseados em estruturas de poços quânticos múltiplos de InGaAs/InAlAs que operam em 1,55 ym, é notavelmente melhorado quando é introduzida uma composição de 52% de Ga na liga e se tem um poço de ~100 A de espessura. Nesse caso, os moduladores possuem uma elevada figura de mérito e podem ser insensíveis à polarização. Nesse estudo foram crescidas várias amostras onde foi analisado o aumento na taxa de crescimento e a variação na composição das ligas de InGaAs e InAlAs em material bulk e em poços quânticos de InGaAs/InAlAs em função da geometria da máscara utilizada, i.e. diferentes larguras do dielétrico e largura da janela onde ocorre o crescimento fixo. Finalmente foram processados guias de onda cujas estruturas foram crescidas com a técnica de crescimento seletivo. Esses guias foram caracterizados por técnicas de campo próximo.
The monolithic integration of a modulator with a waveguide is a lot of interest for application in optical communications for the fact in that can decrease the losses for optical joining between the two devices and to use short modulators that operate in high rates of transmission data. The selective growth is at the present time, one the more promising technique for application in the monolithic integration of semiconductors device. This technique allows to control the thickness and the stress of the grown layers allowing to improve the integration and the characteristics of the devices structures. These thesis is about the implementation, study and application of the selectuve growth by MOCVD of both match and tensile structures of multi quantum wells of inGaAs/InAlAs for the production of the amplitude modulators based on the Stark effect and its integration with waveguide. The performance of the modulators based on structures of multi quantum wells of InGaAs/InAlAs operating in 1,55 um, is notably improved whena Ga composition of 52% is used and the thickness of a quantum well is near to ~100 A. In that case, the modulators have a high figured of merit and they can be insensitive to the polarization. In this study, several samples was grown and the growing rate increase was analyzed and the variation of the composition in InGaAs and InAlAs in bulk alloys and in quantum wells of InGaAs/InAlAs in function of the window where the growth is spent. Finally, waveguides were processed whose structures were grown with the technique of selective growth. Those guides were characterized by the near field technique.
24
Landgraf, Boris [Verfasser], and Wolfgang [Akademischer Betreuer] Hansen. "Structural, magnetic and electrical investigation of Iron-based III/V-semiconductor hybrid structures / Boris Landgraf. Betreuer: Wolfgang Hansen." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1048626555/34.
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25
Lindberg, Martin. "Mode Matching Analysis of One-Dimensional Periodic Structures." Thesis, KTH, Elektroteknisk teori och konstruktion, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231842.
Повний текст джерелаАнотація:
In this thesis, we analyze the electromagnetic wave propagation in waveguidestructuresexhibiting periodical geometry, including glide symmetry. The analysisis performed using a mode matching technique which correlates the different modecoefficients from separate but, connected regions in the structure. This technique isused to obtain the dispersion diagrams for two one-dimensional periodic structures:a glide-symmetric corrugated metasurface and a coaxial line loaded with periodicholes. The mode matching formulation is presented in Cartesian and cylindricalcoordinate system for the former and the later, respectively. The mode matchingresults are compared to simulated results obtained from the Eigenmode Solver inCST Microwave Studio and are found to agree very well.I detta examensarbete, analyseras elektromagnetisk v°agutbredning i periodiskav°agledarstrukturer som uppvisar glid symmetri. Analysen genomf¨ordes genom enmod matchnings-teknik som korrelerar de olika mod-koefficienterna fr°an separeraderegioner i strukturen med varandra. Denna teknik anv¨ands f¨or att ta framdispersionsrelationen f¨or tv°a endimensionella periodiska strukturer: en glid symmetriskkorrugerad meta-yta och en koaxial ledare belagd med periodiskt urgr¨opdah°aligheter. Mod matchnings-formuleringen presenteras i Kartesiska och cylindriskakoordinatsystem respektive f¨or de ovan n¨amnda fallen. Mod matchnings-resultatenj¨amf¨ors med data-simulerade resultat erh°allna fr°an CST Microwave Studio och de¨overenst¨ammer v¨al med varandra.
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Vu, Thi Nhung. "Composants optoélectroniques à faible consommation en III-V sur silicium." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS172/document.
Повний текст джерелаАнотація:
La photonique sur silicium est envisagée comme une solution technologique très prometteuse pour le remplacement des interconnexions électriques par des interconnexions optiques devant se produire dans les prochaines années. Des dispositifs optoélectroniques comme des sources lasers, des modulateurs et des détecteurs, ont été développés pour la réalisation de circuits intégrant des émetteurs/récepteurs. Parmi les défis devant être relevés pour faire avancé la photonique sur silicium, la réduction de la consommation électrique du modulateur est un point crucial. L’intégration des composants passifs et actifs en utilisant une seule et même technologie est également un enjeu majeur pour les futurs systèmes de communication optique. Grâce au développement de l'intégration hybride de semi-conducteurs III-V sur silicium pour la réalisation de sources laser sur silicium, de nouvelles voies peuvent être envisagée pour réaliser des modulateurs optiques et des photodétecteurs efficaces et compacts. De plus, les cristaux photoniques 2D (PhC) et spécifiquement les structures à ondes lentes, qui sont connues pour renforcer les interactions entre la lumière et la matière peuvent apporter des solutions intéressantes pour diminuer de manière ultime la puissance consommée.Dans ce contexte, les travaux menés durant ma thèse ont porté plus spécifiquement sur la conception, la fabrication et la caractérisation de modulateurs à électro-absorption à onde lente en semiconducteur III-V sur silicium. Dans une première partie consacrée à la modélisation, une attention particulière est portée à la conception du cristal photonique et au couplage de la lumière du guide silicium vers l’onde lente. Les performances de la structure optimisée sont aussi analysées, donnant un modulateur de seulement 18.75 µm de longueur fonctionnant à 15 GHz avec un taux d’extinction supérieure à 5 dB sur une gamme spectrale supérieure à 10 nm. Par la suite, l’ensemble des procédés de nanotechnologies durant la thèse pour la fabrication des dispositifs sont présentés. Enfin, les résultats expérimentaux obtenus au cours de cette thèse démontrent l’effet Stark Confiné Quantiquement et l’effet de photodétection obtenu sur les structures intégrées.Les perspectives de ce travail de thèse concernent la réalisation de circuits intégrés photoniques complets, incluant sources lasers, modulateurs à électroabsorption et photodétecteurs en utilisant une seule et même technologieSilicon photonics is considered as a promising solution to replace electrical interconnections in the next years. Among the remaining challenges, the driving power of the active devices has to be minimized. Furthermore the use of a common technological platform for the realization of Silicon (Si) photonics passive and active devices would present a great interest in term of fabrication complexity and cost. III-V on Si is a good candidate for such a common technological platform as the physical properties of III-V semiconductors allow for active functionalities such as III-V on Si laser which have already been successfully demonstrated. In this perspective, 2D photonic crystals (PhCs) and slow light structures, which are known to intrinsically reinforce light/matter interactioncan alsobring interesting opportunities.In this context, the work is focused on the design, fabrication and characterization of slow-light III-V- on-silicon electroabsorption modulators. In a first part, the photonic crystal structure and light coupling from silicon waveguide to slowlight III-V waveguide are designed and modeled. The performance of the optimized structure is analyzed, showing a modulator operating at 15 GHz and exhibiting an extinction ratio of more than 5 dB over a spectral range of more than 10 nm, using a 18.75 µ;m-long modulator. Subsequently, the masks and fabrication steps for a hybrid III-V photonic crystalon Si modulators are presented. Finally, the experimental results obtained during this thesis are presented, showing Quantum Confined Stark Effect and photodetection in the waveguide integrated structures.The reported works open perspective towards the integrating of optical modulators with III-V on silicon nanolasers and photodetectors using a single technology
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Haddad, Mouloud. "Effets du soufflage sur les structures cohérentes dans un canal bidimensionnel." Valenciennes, 2006. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/1e9d7db4-2076-47bd-a014-c694d097d384.
Повний текст джерелаАнотація:
Le contrôle de la turbulence trouve son intérêt dans de nombreux domaines tels que les transports et l’environnement, avec pour objectif la réduction ou l’augmentation du frottement et des phénomènes de transfert. Les techniques mettant en œuvre des jets synthétiques pour contrôler la couche limite sont parmi les plus utilisées. Dans cette étude, les effets d’un soufflage localisé à travers une bande poreuse sur un écoulement turbulent pleinement établi dans un canal bidimensionnel ont été étudiés. Les mesures ont été réalisées pour trois taux de soufflage : 3%, 5% et 8% de la vitesse maximale. Les résultats de cette étude montrent que le soufflage affecte de manière significative les structures turbulentes de la région allant de la paroi jusqu’à la zone tampon. Les profils de vitesse obtenus à l’aide de l’anémométrie à fil chaud présentent des caractéristiques voisines d’un écoulement avec une réduction de frottement pariétal. L’injection accroît fortement toutes les tensions de Reynolds. Les corrélations spatio-temporelles entre la vitesse et le frottement pariétal obtenues respectivement par fils et films chaud, montrent que le soufflage accroît l’angle d’inclinaison des structures cohérentes dans les plans (x,y) et (x,z). Ces résultats ont été confirmés et précisés par la PIV. L’analyse conditionnelle sur les signaux anémométriques montre que le soufflage a pour effet de réduire le temps moyen entre "burst". Tous ces résultats montrent que l’injection à travers la bande poreuse a pour effet de détruire les grosses structures cohérentes dans la zone de proche paroi et permettent ainsi de contribuer à une meilleure compréhension des mécanismes de la turbulenceThe control of turbulence and its concomitant phenomena are important for transport and environmental problems with aim to reduce or increase the skin friction and transfer phenomena. Various techniques can be achieved to perform the control of the boundary layer, the synthetic jet is one of the most popular. In this study, the effects of blowing through a porous strip in a turbulent channel flow were experimentally studied. Measurements were carried out for three blowing rates 3%, 5% and 8% of the velocity at the center of the channel. The results of the present study showed that blowing affects significantly the turbulent structures in the near wall region. Velocity profiles obtained with hot-wire anemometry show similar trends to those of a flow with a reduced skin friction. The wall blowing increases the turbulence intensities and the Reynolds shear stress. The analysis of the anisotropic invariant map indicated that with blowing, the anisotropy level in the near wall region appears to be lower than that of the unperturbed layer. Space-time correlations performed with hot-wire and hot-film show that the inclination angles in (x,y) and (x,z) planes increase with injection. These trends were confirmed by the PIV visualisations. The conditional analysis showed that the mean time between "bursts" is reduced with blowing. The results of the study suggest that blowing stimulates the break-up of the large structures in the near wall region and lead to a better acknowledgement of the turbulence mechanisms
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Šedý, Michal. "Analýza lokalizace inverzních repetic v bakteriálních genomech." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-449791.
Повний текст джерелаАнотація:
Inverted repeats (IR) are common part of DNA of all living prokaryotic and eukaryotic organisms. Inverted repeats plays an important role in the regulation of basics cells processes. They are responsible for formation of cruciform structures. Inverted repeats also cause genomic instability and can be a source of numerous mutations. Cruciform structures can be recognized by DNA-binding proteins and can also act as a transcriptional regulators. Using the Palindrome Analyser tool, the frequency of IR and localization of inverted repeats in bacterial genomes was analyzed. The frequency of IR across the bacterial genome is variable. The frequency of short inverted repeats shows an approximately quadratic dependence on the %GC content in the genome with a minimum of about 50% of GC content. The localization of inverted repeats with respect to “annotated features” show a non-random distribution. The frequency of IR for most features is higher “outside” than “inside”.
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Zaraket, Jean Gerges. "Étude de la fiabilité des structures silicium employées dans le domaine des énergies renouvelables suite à leur fonctionnement sous conditions extrêmes." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0244/document.
Повний текст джерелаАнотація:
Le travail de la thèse proposé consiste à étudier, caractériser et modéliser la performance et la fiabilité de composants semi-conducteurs sous conditions extrêmes c’est à dire pendant et après que ces composants ont subi un stress électrique, un stress thermique voire les deux stress en même temps. Les composants semi-conducteurs que nous avons étudiés sont des modules photovoltaïques en silicium monocristallin pour des applications dans les énergies renouvelables. Dans cette étude, ces composants ont été soumis à plusieurs types de dégradations générant des défauts localisés dans la structure des composants. Dans un premier temps, des études approfondies des caractéristiques I(V) et C(V) et des paramètres électriques des modules solaires photovoltaïques ont été réalisées en testant une série de modules sous différentes conditions environnementales afin de fournir des données pertinentes pouvant être utiles pour l'évaluation des performances, la modélisation du fonctionnement et pour la mise en œuvre correcte et complète des modules photovoltaïques. Ces caractérisations ont été complétées par l’étude des défauts créés à l’interface et dans les structures des modules photovoltaïques par les différents stress sur la base de mesures effectuées sur ces mêmes cellules par la technique Deep Level Transient Spectroscopy (DLTS). Grâce à cette technique, nous avons identifié et localisé ces défauts au sein du composant, en déterminant leur énergie d’activation et leur section efficace de capture. Les résultats de notre étude montrent ainsi l’importance des conditions de fonctionnement sur les performances instantanées et sur le long terme des systèmes photovoltaïques. Ils peuvent être exploitables directement dans la conception même des modules silicium voire transposable, en suivant la méthodologie de l’étude que nous proposons à de nouvelles technologies de modulesThe objective of this work aim to study the performance, reliability of semiconductor structures after their operation under extreme conditions, during and after electrical stress, thermal stress, and combined electro thermal stresses. The studied semiconductor structures are photovoltaic cells for applications in the field of renewable energies. These devices have been exposed to several types of degradation generating localized defects in the structures. The I (V) and C (V) characteristics and electrical parameters have been studied before and after each stress case. The Deep Level Transient Spectroscopy (DLTS) was used as advanced technique for tracking the defects created at the interface and in the bulk structures. The DLTS technique allows identifying and locating these defects within the devices, by determining their activation energy and their capture cross-Section
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Muchna, Jan. "The Bankruptcy Rules in Linear Ordered Structures." Master's thesis, Vysoká škola ekonomická v Praze, 2009. http://www.nusl.cz/ntk/nusl-81888.
Повний текст джерелаАнотація:
The bankruptcy problem involves the distribution of perfectly divisible goods. Particular attention is paid to the situations, where the amount of goods available is not enough to cover the demand. An example of real life situations that can be solved using various bankruptcy rules may be a division of a heritage or when a company goes bankrupt and its estates are sold to satisfy interested parties' claims. This paper introduces to the problem a linear structure of the participants, meaning that participants are now satisfied one after another in a preset order. It applies the equal awards (CEA) and the equal losses (CEL) solutions on the revised problem. Since their axiomatization is no longer valid, both solutions are extended and new characterizations are given in the thesis. The thesis contains a series of original proofs for both extended solutions and whole problem is examined in the setting of the well-known river sharing problem.
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Hale, Michael J. "Characterization of the atomic and electronic structures of oxide/III-V(001) interfaces /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3144334.
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Nicoll, Christine Anne. "MBE growth and low-temperature characterization of low-dimensional III-V semiconductor structures." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614005.
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Garawal, Nirmal Singh. "Photoreflectance and spectroscopic ellipsometry of lattice matched and strained multilayer III-V structures." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/842932/.
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Room temperature Photoreflectance and Spectroscopic Ellipsometry were used to study the valence band axial strain deformation potential in pseudomorphic strained In2Ga 8As on GaAs, the band offsets in strained single quantum wells of In 2Ga 8As with AlyGa(1-y)As (y=0, 5, 10 and 20%) barriers on GaAs and the composition and thicknesses of lattice matched (Ga, As, In, Al, P) -based multilayers. The samples were grown by MBE and MOVPE. The photoreflectance spectra from a number of In gGa gAs layers with thicknesses from lOOA to 8000A grown on GaAs substrates were measured. They showed clear, well defined structures attributed to the splitting of the valence band into the Mj=+/-3/2,+/-l/2 manifolds. Their separation was observed to decrease and their overall position to move to lower energy with increasing thickness. Complex GaAs substrate structures were also observed whose shape was attributed to interference. The spectra were modelled using a Kramers-Kronig transformation to deduce the number, magnitude and broadening of the oscillators needed for a least-squares fit using Aspnes' third derivative functional form for a 3d critical point. Excellent fits were obtained which are unrivalled in previous PR analysis. The position of the strained split structures corresponded well with the measured strain from x-ray analysis and theory. From these splittings, values of the axial deformation potential, b, were obtained in the range -2.5 to -1.54eV. The photoreflectance from the single quantum wells showed clear, complex spectra. Good fits were obtained using the third derivative functional form (TDFF) for a 2d critical point. Both symmetry allowed and forbidden transitions were observed. The predicted transitions were calculated using an effective mass formalism. Reasonable agreement with the experimentally observed confined transition energies was found. The band offsets were estimated by allowing the theoretical offsets, determined from the theory of Van der Walle, to vary until a good match with observed transitions was obtained. Conduction to valence band offset values of 60:40 +/-8% were obtained, well within the range predicted by other workers. Spectroscopic ellipsometry has been used to measured the compositions and thicknesses of two-, three-, and four-layer structures consisting of Al2Ga8As/GaAs and In53Ga47As/Al48Ga52As/InP lattice matched materials. A simple procedure was developed to obtain the dielectric values of Al48In 52AS by scaling InP values. These were used to simulate the test structures. Very good agreement with destructive techniques have been obtained. These were compared to the thickness values obtained using actual measured Al48In52As reference data.
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Buček, Petr. "Využití techniky orientovaných fólií v TEM." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228855.
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The master’s thesis is focused on the application of the technique of oriented foils in transmission electron microscopy. Dislocation structures were identified by this technique in both phases of polycrystalline austenitic-ferritic stainless steel SAF 2507 formed during low cycle fatigue at two plastic strain amplitudes ap. In individual grains the stress axis and the Schmid factors of active slip systems were determined. In austenitic grains, the planar structures were determined at both ap. In ferritic grains, the dislocation arrangement was different for the two observed ap. Individual screw dislocations and pile-up´s of edge dislocations were found at low ap = 1x10-4. Mixture of vein and wall dislocation structures were formed at high ap = 2x10-3. Observed dislocation structures were discussed in relation with the cyclic plastic response of the duplex stainless steel.
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Dadgostar, Shabnam. "(Al,Ga)(As,P) structures in the GaP matrix." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17576.
Повний текст джерелаАнотація:
GaP ist ein Halbleiter mit einer großen Bandlückenenergie und infolgedessen transparent im größten Teil der sichtbaren Wellenlängen. GaP hat außerdem die kleinste Gitterfehlanpasung zu Si (weniger als 0.4%). Das macht GaP ein interessantes Material für monolithische Integration zu III–V Lichtsender auf Si. Diese Arbeit ist eine Untersuchung über die strukturellen und optische Eigenschaften von (Al, Ga) (As, P) Heterostrukturen auf GaP (001) -Substrat aufgewachsen. Die Einflüsse des PH3 Fluss und Wachstumstemperatur untersucht auf dem Kristallqualität und Oberflächenqualität von AlGaP/GaP Heterostructure. Experimentelle Ergebnisse deuten darauf hin, dass eine Wachstumstemperatur von 490 oC und ein geknackter (engl. cracked) PH3 Fluss von 2.7 sccm zur besten AlGaP Qualität und gleichzeitig zur guten GaP Qualität führen. Um die ineffiziente Lichtemission von GaP zu überwinden wurde GaAs in der GaP-Matrix gewachsen. Die Entstehung der Quantenpunkte wurde durch die 3.7% Gitterfehlanpassung zwischen GaAs und GaP für GaAs Nenndicke über 1,2 ML. Die optischen Messungen zeigen zwei Peaks im Bereich von 1,7 bis 2,1 eV und die Lumineszenz auf Raumtemperatur für 2,7 und 3,6 ML-Proben. Die hohe Energieemission wird der indirekten Rekombination in den dünnen Quantentröge oder kleine gespannte Quantenpunkte zurückzuführen, Während die niedrige Energie Emission ist aufgrund der direkten Elektron-Loch- Rekombination in der entspannten Quantenpunkte. Die Wirkung von Al wird untersucht auf die energetische Bandausrichtung und auf die elektronische Struktur der (Al,Ga)As Quantenstrukturen. Die optische Spektren zeigten einen blaue Verschiebung (engl. blue shift) mit wachsendem Al-Inhalt und die höchste missionsenergie für die (Al,Ga)As/GaP- Heterostruktur war 2.17 eV die zum indirekten Typ-II-Rekombination zusammenhängt.Transparency of GaP due to the large indirect bandgap energy and its small lattice mismatch with Si make GaP an interesting candidate for optoelectronic devices in visible wavelength. This thesis is an investigation on the structural and optical characteristics of (Al,Ga)(As,P) heterostructures grown on GaP (001) substrates. The influences of the PH3 flux and growth temperature are studied on the crystal and surface quality of AlGaP/GaP heterostructure. The results indicate the narrow growth window of PH3 = 2.7 sccm and growth temperature = 490oC as the optimized conditions. To overcome the inefficient light emission of indirect GaP, direct bandgap GaAs was grown as the quantum structures in the GaP matrix. The QD formation is driven by the 3.7% lattice mismatch between GaAs and GaP for GaAs nominal thickness above 1.2 ML. The optical measurements show two peaks in the range of 1.7 to 2.1 eV and the luminescence up to room temperature for 2.7 and 3.6 ML samples. The high energy emission is attributed to indirect carrier recombination in the thin quantum wells or small strained quantum dots, whereas the low energy red emission is due to the direct electron-hole recombination in the relaxed quantum dots. The influence of the Al content on the band alignment and electronic structure of (Al,Ga)As quantum structures is studied. The optical spectra illustrate the blueshift of the radiative emission with increasing the Al content and the highest emission energy of 2.17 eV is observed for the (Al,Ga)As/GaP system that is related to the indirect type-II radiative recombination.
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Roque, Joyce. "Corrélation luminescence/défauts étendus dans les structures à puits quantique InGaAs épitaxiées sélectivement sur substrats Si." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY082/document.
Повний текст джерелаАнотація:
Les semi-conducteurs III-V présentent des propriétés remarquables de mobilité électronique et d’émission optique. La croissance de ces matériaux par MOCVD sur substrat silicium (001) en 300 mm offre l’opportunité de réaliser les composants bas coût, et d’apporter de nouvelles fonctionnalités à la microélectronique silicium par l’intégration de composants électroniques et optiques. De ce fait, la croissance de semi-conducteurs III-V sur silicium a connu un engouement important au cours de ces dernières années. De telles intégrations monolithiques impliquent de développer des couches III-V de très bonne qualité épitaxiées sur silicium. Actuellement, le principal enjeu réside dans la réduction des densités de défauts cristallins tels que les fautes d’empilement, parois d’antiphase et dislocations. L’impact de ces défauts structuraux sur ces propriétés reste encore aujourd’hui principalement étudié à l’échelle micrométrique (effet Hall, photoluminescence,…) ne présentant pas de résolution spatiale suffisante permettant pas de dissocier les différents paramètres physico-chimiques. Ces développements nécessitent en conséquence des moyens adaptés de caractérisation pour contrôler et connaitre les propriétés physico-chimique de ces couches III-V épitaxiée sur Si.Le travail de cette thèse porte sur le développement d’une méthode destinée à corréler spatialement à l’échelle nanométrique les propriétés optiques et les caractéristiques morphologiques de couches III-As crues par MOCVD sur Si (001) en 300mm. Elle a permis d’étudier des puits quantiques d’InGaAs épitaxiés sur buffer GaAs et sur substrat Si avec pour méthode de réduction des défauts émergeants l’utilisation de couches tampons à base de GaAs et la croissance localisée entre murs d’oxydes (aspect ratio trapping (ART)). L’étude s’est appuyée sur deux techniques de caractérisation: La cathodoluminescence (CL) permettant d’observer spatialement sur l’échantillon bulk l’énergie d’émission et l’intensité correspondantes d’un puits quantique d’InGaAs, et la microscopie électronique en transmission (STEM/TEM) en lame mince donnant des informations quantitatives sur la morphologie de la structure (épaisseurs des couches, position des défauts, stoechiométrie…). Nous avons développé une méthode qui permet de corréler spatialement les résultats de ces deux techniques de caractérisation. La méthode consiste en plusieurs marquages spécifiques réalisés par faisceau d’électron pour repérer et extraire précisément les zones d’intérêt observés en cathodoluminescence. Des mesures de déformation (N-PED) sur lame mince ont également été réalisées.Cette méthode de caractérisation corrélée a permis de mettre en évidence des modifications des propriétés physico-chimique de puits quantiques d’InGaAs à l’échelle nanométrique directement liées aux conditions de croissance, et à la présence de défauts émergentsIII-V semiconductors have remarkable properties of electronic mobility and optical emission. Their growth by MOCVD on 300 mm (001) silicon substrate offers the opportunity of manufacturing at low cost and to get new functionalities in microelectronic devices for electronic components and optical emitters. Thereby III-V growth on silicon has been a huge success in recent years. Monolithic integrations imply to develop very good quality of III-V layers epitaxied on silicon. That is why currently, the major issue is to reduce crystalline defect density such as stacking faults, antiphase boundaries and dislocations. Structural defects which impact these properties are still mainly studied at micrometric scale (Hall effect, photoluminescence,…) but they not have sufficient spatial resolution to dissociate the different physicochemical parameters. Consequently, these developments require adapted characterizations to control and to obtain physicochemical properties of III-V epitaxied layers on Si.The aim of this thesis is to develop a method to spatially correlate at nanoscale optical properties and morphological characteristics of III-As layers grown by MOCVD on 300 mm (001) Si. In the frame of this thesis, this method allowed to study InGaAs quantum wells (QW) epitaxied on GaAs buffer and on Si substrate with defect density reduction method the use of GaAs buffer layers and patterned growth (aspect ratio trapping (ART)). The study is based on two characterization techniques : cathodoluminescence (CL) which allows to spatially observe on bulk sample InGaAs QW energy emission and intensity, and transmission electronic microscopy (STEM/TEM) of thin lamella which give quantitative information on the morphology (layer thicknesses, defect positions, stoichiometry,…). The method developed allows to spatially correlate results of these two techniques. It is to realize several specific marks made by electron beam to localize and precisely extract interesting areas observed by CL. Strain measurements (N-PED) on TEM lamella is realized too.This correlated characterization method has highlighted physicochemical property modifications of InGaAs QW at nanoscale directly related to growth conditions and to threading dislocations presence
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Ikpi, Magdalene Edet. "Growth and charaterisation of III-V semiconductor quantum dot structures on GaAs patterned substrates." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613730.
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Mazet, Lionel. "Réalisation et caractérisation de structures micro-électroniques à base de semiconducteur III-V(InP)." Clermont-Ferrand 2, 2004. http://www.theses.fr/2004CLF22551.
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Ce mémoire relate l'étude de capteurs de gaz réalisés à base de jonctions pseudo-Schottky (Pd/InP). Ces structures micro-électroniques ont pour objectif la détection et la quantification des gaz oxydants (dioxyde d'azote et ozone) intervenant dans la pollution atmosphérique. Après une description des différentes espèces gazeuses constituant la pollution de l'air troposphérique, de la réglementation en vigueur et des méthodes de mesures des différents polluants, les principales familles de capteurs de gaz potentiellement utilisables dans ce domaine sont détaillées. L'étude des jonctions Métal-Semiconducteur, abordée par l'intermédiaire des deux modèles classiques de Schottky-Mott et de Bardeen, met en evidence l'influence des états d'interface et l'intérêt de réaliser des structures pseudo-Schottky. Des mesures en laboratoire à températures et concentrations variables en NO2 et O3 sont présentées. Elles permettent, en corrélation avec des études XPS et AFM, d'interpréter les interactions gaz/ matériaux et de mettre en évidence la présence d'oxyde de surface et subsurface sur le palladium. Ces tests démontrent la bonne sensibilité et la bonne reproductibilité du capteur vis-à-vis du dioxyde d'azote ainsi que la sélectivité à l'ozone, confirmée lors de tests en atmosphère urbaine sur des sites de mesures d'Atmo Auvergne. Afin d'optimiser les caractéristiques métrologiques de ces capteurs, une méthodologie de mesure originale, basée sur la cinétique réactionnelle associée à une régénération du capteur (augmentation de température associée à l'action d'un gaz réducteur) est présentée. Cette méthodologie permet d'obtenir des mesures reproductibles, en temps réel, des concentrations de dioxyde d'azote et d'ozone
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Minutillo, Nicholas G. "The Growth and Characterization of Gallium Arsenide Nanowire Structures by Metal Organic Chemical Vapor Deposition." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1416593665.
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Huková, Martina. "Stavebně technologická příprava prodejny Smart Light v Bratislavě." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392005.
Повний текст джерелаАнотація:
The main subject of this diploma thesis is elaboration of construction and technological preparation for the main structure of the Smart Light shop in Bratislava. For main structure has been processed time schedule of the construction, single item budget, machine configuration design, drawing of building site, coordination situation of the building with connection to the infrastructure, safety and health protection during work on building site. Part of the thesis is processing study of main construction technological parts. Diploma thesis in technological prescript focuses on implementation of floor structure with cast epoxy walking surface. There has been elaborated testing and quality plan of this technological part. Additional chapter approximates built-in technology – cooling ceiling structure. For elaboration of this diploma thesis were used programs AutoCAD, CONTEC, BuildPowerS, Microsoft Excel, Microsoft Word.
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Vlachová, Hutová Eliška. "STUDIUM ZMĚN VLASTNOSTÍ BIOLOGICKÝCH MATERIÁLŮ V ELEKTROMAGNETICKÝCH POLÍCH." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-447546.
Повний текст джерелаАнотація:
Presented dissertation discusses the influence of electromagnetic fields on the weight of the particles, which are considered in this work as substances with the hub. Theoretical knowledge was practically tested on plant organisms (early somatic embryos, fungal pathogens), theoretically the influence of electromagnetic field on cell structure was modeled. It was subsequently confirmed by a practical experiment assumption about the influence of electromagnetic fields on the weight of the particles. These experiments were preceded by a theoretical study of the problem and the formulation of a solution using Maxwell's equations, from which other descriptive equations and formulas were derived. The results of the experiments were presented at several professional conferences and published in professional journals and proceedings.
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Komoráš, Miroslav. "Pulsace toku kapaliny v pružné trubici." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401537.
Повний текст джерелаАнотація:
This master’s thesis is dealing with analysis of fluid flow pulse in a flexible tube representing e.g. an artery in a human body. In ANSYS program, 3D simulations were performed, and these are so-called interrelated FSI analysis. In Maple software, 1D simulations of fluid flow in the tube were performed for various thin-walled and thick-walled variants. The aim is using these programs to determine the flow rates and pressures in the tube, its wall deformation and stress. Therefore, the theoretical part deals mainly with basic equations of flow dynamics, linear and nonlinear models and rotationally symmetric vessels. In the computational part are described individual procedures in the mentioned programs.
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Honzárek, Pavel. "Viladům Kasalka v Humpolci." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227232.
Повний текст джерелаАнотація:
This diploma thesis deals with the project documentation of villa house Kasalka in Humpolci. The house is situated in the region Highland in the village Humpolec, cadastral territory of Humpolec. The building is designed as a five-story brick building, where the vertical structures are designed from a structural system POROTHERM. The external walls are insulated. The building is covered with three flat roof decks at different heights, two of which are walkable and used as terraces. The building includes Garage for ten cars of type 1a and small establishment an office type.
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Brown, James Emery. "Advances in electrical energy storage using core-shell structures and relaxor-ferroelectric materials." Diss., Kansas State University, 2018. http://hdl.handle.net/2097/38779.
Повний текст джерелаАнотація:
Doctor of PhilosophyDepartment of Chemistry
Jun Li
Electrical energy storage (EES) is crucial in todays’ society owing to the advances in electric cars, microelectronics, portable electronics and grid storage backup for renewable energy utilization. Lithium ion batteries (LIBs) have dominated the EES market owing to their wide use in portable electronics. Despite the success, low specific capacity and low power rates still need to be addressed to meet the increasing demands. Particularly, the low specific capacity of cathode materials is currently limiting the energy storage capability of LIBs. Vanadium pentoxide (V₂O₅) has been an emerging cathode material owing to its low cost, high electrode potential in lithium-extracted state (up to 4.0 V), and high specific capacities of 294 mAh g⁻¹ (for a 2 Li⁺/V₂O₅ insertion process) and 441 mAh g⁻¹ (for a 3 Li⁺/V₂O₅ insertion process). However, the low electrical conductivities and slow Li⁺ ion diffusion still limit the power rate of V₂O₅. To enhance the power-rate capability we construct two core-shell structures that can achieve stable 2 and 3 Li⁺ insertion at high rates. In the first approach, uniform coaxial V₂O₅ shells are coated onto electrospun carbon nanofiber (CNF) cores via pulsed electrodeposition. The materials analyses confirm that the V₂O₅ shell after 4 hours of thermal annealing at 300 °C is a partially hydrated amorphous structure. SEM and TEM images indicate that the uniform 30 to 50 nm thick V₂O₅ shell forms an intimate interface with the CNF core. Lithium insertion capacities up to 291 and 429 mAh g⁻¹ are achieved in the voltage ranges of 4.0 – 2.0 V and 4.0 – 1.5 V, respectively, which are in good agreement with the theoretical values for 2 and 3 Li⁺/V₂O₅ insertion. Moreover, after 100 cycles, remarkable retention rates of 97% and 70% are obtained for 2 and 3 Li⁺/V₂O₅ insertion, respectively. In the second approach, we implement a three-dimensional (3D) core-shell structure consisting of coaxial V₂O₅ shells sputter-coated on vertically aligned carbon nanofiber (VACNF) cores. The hydrated amorphous microporous structure in the “as-deposited” V₂O₅ shells and the particulated nano-crystalline V₂O₅ structure formed by thermal annealing are compared. The former provides remarkably high capacity of 360 and 547 mAh g⁻¹ in the voltage range of 4.0 – 2.0 V and 4.0 – 1.5 V, respectively, far exceeding the theoretical values for 2 and 3 Li⁺/V₂O₅ insertion, respectively. After 100 cycles of 3 Li⁺/V₂O₅ insertion/extraction at 0.20 A g⁻¹ (~ C/3), ~ 84% of the initial capacity is retained. After thermal annealing, the core-shell structure presents a capacity of 294 and 390 mAh g⁻¹, matching well with the theoretical values for 2 and 3 Li⁺/V₂O₅ insertion. The annealed sample shows further improved stability, with remarkable capacity retention of ~100% and ~88% for 2 and 3 Li⁺/V₂O₅ insertion/extraction. However, due to the high cost of Li. alternative approaches are currently being pursued for large scale production. Sodium ion batteries (SIB) have been at the forefront of this endeavor. Here we investigate the sodium insertion in the hydrate amorphous V₂O₅ using the VACNF core-shell structure. Electrochemical characterization was carried out in the potential ranges of 3.5 – 1.0, 4.0 – 1.5, and 4.0 – 1.0 (vs Na/Na⁺). An insertion capacity of 196 mAh g-1 is achieved in the potential range of 3.5 – 1.0 V (vs Na/Na⁺) at a rate of 250 mA g⁻¹. When the potential window is shifted upwards to 4.0 – 1.5 V (vs Na/Na⁺) an insertion capacity of 145 mAh g⁻¹ is achieved. Moreover, a coulombic efficiency of ~98% is attained at a rate of 1500 mA g⁻¹. To enhance the energy density of the VACNF-V₂O₅ core-shell structures, the potential window is expanded to 4.0 – 1.0 V (vs Na/Na⁺) which achieved an initial insertion capacity of 277 mAh g⁻¹. The results demonstrate that amorphous V₂O₅ could serve as a cathode material in future SIBs.
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Hetherington, Dale Laird. "III-V compound semiconductor integrated charge storage structures for dynamic and non-volatile memory elements." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186112.
Повний текст джерелаАнотація:
This thesis presents an investigation into a novel group of GaAs charge storage devices. These devices, which are an integration of bipolar and junction field effect transistor structures were conceived, designed, fabricated, and tested within this study. The purpose was to analyse new types of charge storage devices, which are suitable for fabrication and lead to the development of dynamic and nonvolatile memories in III-V compound semiconductors. Currently, III-V semiconductor storage devices consist only of capacitors, where data is destroyed during reading and electrical erasure is difficult. In this work, four devices types were demonstrated that exhibit nondestructive reading, and three of the prototypes can be electrically erased. All types use the junction field effect transistor (JFET) for charge sensing, with each having different bipolar or epitaxial layer structure controlling the junction gate. The bottom epitaxial layer in each case served as the JFET channel. Two of the device types have three alternately doped layers, while the remaining two have four alternately doped layers. In all cases, removal of majority carriers from the middle layers constitutes stored charge. The missing carriers deplete the current carrying a region of the JFET channel. Drain current of the JFET becomes an indicator of stored charge. The basic function of each JFET memory element type is independent of interchanging n- and p- type doping within the structure type. Some performance advantage can be realized, however, by sensing with an n-type channel as compared to p- type due to increased carrier mobility. All device types exhibit storage time characteristics of order ten seconds. Devices are constructed in epitaxial layers grown by molecular beam epitaxy (MBE) reactors. The design of the epitaxial layers is an intrinsic part, together with the electrical design, of the storage device concept. These concepts are implemented first with photolithography masks which are used in device fabrication. The fabrication methods employ wet chemical etching and ohmic metal liftoff techniques. Electrical dc and charge retention time characteristics along with functionality read/write operations for the memory element group are measured using commercial electronic test equipment.
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Jones, Steven Alan. "Refinement of TI-6%AL-4%V weld metal structures during gas-tungsten arc welding." Thesis, Open University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288987.
Повний текст джерела
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Halioua, Yacine. "Etude de structures hybrides : lasers à cristaux photoniques en semi-conducteurs III-V sur silicium." Paris 7, 2011. http://www.theses.fr/2011PA077169.
Повний текст джерелаАнотація:
La demande grandissante relative au transfert de données à très haut débit rencontre aujourd'hui les limites des systèmes ou circuits micro-électroniques. Il est actuellement admis qu'un transfert de données par flux lumineux permettra de significativement lever ces limites en terme de vitesse du point de vue de la communication inter- et intra-composants électroniques. Plus particulièrement, du fait de leurs propriétés intrinsèques, la combinaison de structures actives en semi-conducteur III-V et de structures passives en Silicium, dans un schéma compatible avec les procédés CMOS, ouvre d'intéressantes perspectives dans ce sens. Dans ce contexte, la présente thèse traite de la conception, la réalisation et l'étude de structures hybrides à deux niveaux composées de cristaux photoniques (CPs) en semi-conducteurs III-V couplés à un guide en Silicium. Les deux niveaux sont liés au moyen d'une couche intermédiaire de BCB. En premier lieu, l'opération laser, à faible seuil, couplée au guide de silicium sous-jacent est démontrée, aussi bien dans le cas de guides que de cavités CPs. Les caractéristiques optiques ainsi que les paramètres pertinents du système sont étudiés expérimentalement et confrontés au travail de modélisation mené en amont. Une extraction, via le guide de silicium, de la lumière émise dans le niveau actif atteignant 90% est ainsi démontrée. Cette valeur à été rendue, notamment, par le développement d'une technologie d'alignement spécifique, permettant une précision de ~25 nm, entre les deux niveaux. Enfin, l'observation de la bistabilité en régime de gain est présentée avant que soient discutées un certain nombre de perspectivesThe ever-growing demand for high data transmission and processing rates is hitting the limits of microelectronic circuits and Systems. It is currently admitted that photons can significantly relieve the speed constraints of inter as well as intra-chip communications. More specifically, due to their inherent advantages, the hybridisation of III-V active and Si passive photonic structures, which are CMOS compatible, opens a new avenue for an exciting field of endeavour. In this context, the present thesis deals with fabrication and study in depth of a two level structure based on III-V photonic crystals (PhCs) evanescently coupled to silicon wires. The two levels are bonded together using an adhesive BCB-based bonding technique. Taking advantage of PhCs properties reasonably low threshold laser operation coupled to the silicon wire underneath is demonstrated, using both PhCs waveguides and wire cavities. The optical characteristics and coupling efficiencies of the System against various parameters were experimentally studied and the results successfully confronted to modelling, showing amongst other results that 90% of the light emitted in the top level is extracted via the silicon wire. Such a high value has been rendered possible by by an important work on modelling and the development of a specific alignment processing procedure providing an accuracy of ~ 25 nm. In conclusion, the observation of low-threshold bistability under gain regime is presented and numerous perspectives are discussed
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Gautier, Sylvestre. "Etudes expérimentales et modélisation de la diffusion du Be dans des structures épitaxiées III-V." Rouen, 1998. http://www.theses.fr/1998ROUES060.
Повний текст джерелаАнотація:
Le sujet de cette thèse concerne la caractérisation et la modélisation de la diffusion du dopant béryllium dans des structures épitaxiées III-V, et plus particulièrement dans les composés ternaires gainas et quaternaires GaInAsP, en accord de maille sur InP. Ces matériaux sont à la base d'une famille de transistors bipolaires a hétérojonctions (TBH), voués à l'intégration optoélectronique des circuits dédiés au traitement des communications par fibre optique. L'obtention de bonnes performances ainsi que l'assurance d'une bonne fiabilité exigent à la fois une parfaite maîtrise, lors de l'élaboration des hétérostructures, de la localisation de la région de base dopée généralement Be, et le maintien de ce confinement sous les contraintes imposées par le fonctionnement (gravure, métallisation,). Des structures épitaxiées représentant des homostructures gainas dont une couche dopée Be (310 1 9 cm 3) est insérée entre deux couches non dopées ont été fabriquées par CBE (Chemical Beam Epitaxy) et GSMBE (Gas Source Molecular Beam Epitaxy). D'autres structures analogues en GaInAsP, ainsi que des hétérostructures GaInAs/InP et GaInAs / GaInAsP ont également été fabriquées par GSMBE. Apres traitement thermique (RTA) de l'ensemble des échantillons dans une gamme de 700-900°C et pour des temps de paliers inférieurs à 4 minutes, les profils de diffusion du Be en profondeur ont été relevés par SIMS (Secondary Ion Mass Spectrometry) et les profils électriques par Polaron. En parallèle avec notre étude expérimentale, plusieurs formes du mécanisme kick-out tirés du modèle substitutionnel-interstitiel de diffusion (SID) ont été implémentés en tenant compte des effets de champ électrique et du niveau de Fermi. En calculant les différents paramètres d'ajustement, les courbes simulées semblent finalement mieux ajuster l'ensemble des profils expérimentaux GSMBE en supposant l'interstitiel de Be neutre.
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Feilhauer, Michal. "Řešení dynamické odezvy vodohospodářských konstrukcí v interakci s kapalinou." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-355595.
Повний текст джерелаАнотація:
Behaviour prediction of hydraulic steel structures with the view to surrounding influences in various design dispositions is a fundamental condition for operational reliability assessment of the analyzed construction. Reliable characteristics of construction behaviour defined by the specification of its movement within changes caused by time and environmental influences is of great importance. In currently used engineering mechanics formulation it concerns setting the response of the defined construction or its part to the given time variable mechanic load. Required response values, which are necessary for evaluation terminal dispositions of capacity and usability of the construction, are trans-location and tension, or values thence derived. Calculation is basic means for response prediction of construction. The thesis presented deals with complex multi-physical behaviour problems of water supply constructions in fluid structure interaction. There are presented various approaches to calculations of static and dynamic qualities of constructions. These approaches are divided into so called “direct method”, which is based on direct connection between two physical fields and the calculation is performed by the method of final elements, and so called “indirect method” , which is based on connection of two physical fields by means of various interfaces, which are described in this thesis. In case of indirect method, the calculation of running liquid is performed by the method of final volumes and the construction calculation is performed by the method of final elements. Within the scope of this thesis, static and dynamic responses of water supply constructions have been solved with the use of the above mentioned approaches. The results of the calculations in the scope of this thesis have been compared with the findings of performed experiments. The final part of the thesis describes the results and generalized findings gathered from the tasks by various approaches.
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Zelenková, Markéta. "Etická dilemata v podnikání, účetnictví a daních." Master's thesis, Vysoká škola ekonomická v Praze, 2015. http://www.nusl.cz/ntk/nusl-205709.
Повний текст джерелаАнотація:
The thesis deals with financial accounting and taxation; i.e. areas with increased risk of unethical behaviour. It presents and critically evaluates the measures introduced by the European Union, the Organisation for Economic Co-operation and Development (OECD) and the authors of Taxparency project - the nongovernmental organisation Transparency International Česká republika and Lexperanto association. The introductory chapters of the thesis offer a brief excursion into the realms of philosophy, law and psychology. Their purpose is to provide a comprehensive summary of the most important findings from these disciplines for better understanding of the meaning and fundamentals of ethics. Subsequently, three key areas of financial accounting and taxation are discussed - non-transparent ownership structures, virtual offices and transfer prices - with the objective to determine the motives of entrepreneurs to use these practices. LuxLeaks case is mentioned as a practical example of unethical behaviour of entrepreneurs, tax advisers as well as of civil servants. The conclusion outlines the Taxparency project. The aim of the thesis is not only to introduce but also critically evaluate the project. Based on the results of a questionnaire survey, the possibilities of the project implementation in the conditions of the Czech Republic are analysed. The official websites of individual institutions and organisations became the main information source for the thesis.