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Dissertations / Theses on the topic 'Electron holes'
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Ouahioune, Nedjma. "Čerenkov emission of whistler waves by electron holes." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-446395.
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Electron holes are positively charged nonlinear structures in which trapped electrons are supported by a positive electrostatic potential. These structure are regularly observed in space and laboratory plasmas by means of diverging bipolar electric field signatures. Recent observations and simulations have shown that fast moving electron holes can generate electromagnetic whistler waves via Čerenkov emission. The fast moving positive charge correspond to localised currents which can potentially excite waves. The aim of the project is to study both theoretically and numerically the properties leading to the Čerenkov emission of whistler waves by three-dimensional electron holes. In addition, efforts are dedicated to the derivation of a model providing the properties of emitted whistlers. The model is compared with the observational features of electromagnetic whistler waves generated by electron holes.
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Zhou, Chuteng. "Computational and theoretical study of electron phase-space holes in kinetic plasma: kinematics, stability and ion coupling." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119039.
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Thesis: Ph. D. in Applied Plasma Physics, Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 181-191).
In this thesis, a comprehensive study of Bernstein-Greene-Kruskal (BGK) mode electron holes in a collisionless plasma where strong kinetic effects are important is presented. Kinematic theory based on momentum conservation is derived treating the electron hole as a composite object to study the dynamics of electron holes. A novel 1-D Particle-In-Cell simulation code that can self-consistently track the electron hole motion has been developed for the purpose of this thesis work. Quantitative agreement is achieved between analytic theory and simulation observations. The thesis reports a new kind of instability for electron holes. Slow electron holes traveling slower than a few times the cold ion sound speed in the ion frame are observed to be unstable to the oscillatory velocity instability. A complete theoretical treatment for the instability is presented in this thesis. Numerical simulations yield quantitative agreement with the analytic theory in instability thresholds, frequencies and partially in instability growth rates. It is further shown that an electron hole can form a stable Coupled Hole Soliton (CHS) pair with an ion-acoustic soliton. A stable CHS travels slightly faster than the ion-acoustic velocity in the ion frame and is separated from a typical BGK mode electron hole in the velocity range by a gap, which is set by the oscillatory velocity instability. Transition between the two states is possible in both directions. A CHS exhibits a soliton-like behavior. The thesis sheds light on solving the ambiguity between an electron hole and a soliton. This thesis work also has important implications for interpreting space probes observations.
by Chuteng Zhou.
Ph. D. in Applied Plasma Physics
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Reinsch, Andreas, and Andreas Reinsch. "Search for Colorful Quantum Black Holes Decaying to an Electron-Jet Final State with the ATLAS Experiment." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12370.
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A search for quantum black holes with color charge decaying to one electron and
one quark has been performed using data collected by the ATLAS Experiment at
the Large Hadron Collider corresponding to 2.29 fb−1. No excess over the expected
Standard Model interactions has been observed. Limits are set on the production
cross section for events with one electron and one jet resulting from new physical
phenomena. Models with a combined invariant mass of the electron and jet larger
than or equal to 2.5TeV and a cross section above 2.6 fb are excluded at the 95%
confidence level. This allows the exclusion of a significant part of the parameter
space of quantum black hole models.
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Bause, Marlon Luis. "Plasma density characteristics of magnetic holes near the Kronian magnetosphere boundary surfaces." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414766.
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Localized structures of the magnetic field strength depression are often observed in the interplanetarymedium, and they are called ‘magnetic holes’ after the original work of Turner et al. 1977. A numberof observations of similar features have been reported, while the mechanisms of their origin have notfully understood yet. The scale size of their structures varies from several to a few thousand of the protongyro radii, and their characteristic orientations of the magnetic field also vary, and therefore differenttypes of the magnetic holes have been suggested. To date, the magnetic holes are classified into Mirrormode and magnetic decreases (Tsurutani et al. 2011). Despite a large number of papers that report theobservational characteristics of the magnetic holes, many identify the feature using only the magneticfield data. This is due to the scale size of the structure at a large speed of the solar wind medium, thespatial resolution of the plasma instruments is often insufficient while the magnetic field instrument canusually obtain the data in high enough time resolution.The Cassini spacecraft orbited Saturn for almost 17 years and obtained a large amount of data in/near theKronian magnetosphere, where the series of the magnetic depletions have been also observed (Smith et al.1980). The Langmuir Probe (LP) onboard Cassini measures the spacecraft potential and, in turn, measuresthe electron density in in-situ in the outer magnetosphere and solar wind region. This measurement hasbeen done using the LP sweep mode which samples the current-voltage curve of the probe every 10 minin the outer magnetosphere. The LP has also been operated in the continuous mode that measures theprobe current at a fixed bias potential every 16 s allowing to calculate the electron density in a smallerscale that is required for the studies magnetic holes. However, there is no general calibration so far inorder to conduct a statistical study in the outer magnetosphere region. The goal of this project is toinvestigate the possibility to use the LP data for the magnetic hole study, calibrate the LP continuousmode to derive the plasma density near the magnetospheric of Saturn, and investigate the scale size of theplasma density structure in the magnetic holes, i. e. plasma β, the field strength and density.The calibration of the continuous data was done by finding a relation between the current at 11 V, whichis a typical bias voltage of continuous mode, and the spacecraft potential obtained by the LP the sweepmode data. Is is expected that the current at 11V is linearly proportional to the floating potential andtherefore can be used to derive the electron density with the potential and density relationship presentedby Morooka et al. 2009. I found that the spacecraft attitude against the sun has a strong effect on therelation, and derived 11V current-floating potential relationship depending on the different spacecraftattitude.Using the LP continuous data calibration above, I investigated the electron density characteristics aroundthe magnetic hold structure, and confirmed that they are generally in anticorrelation relationship. I estim-ated also the plasma β assuming a constant temperature of 100 eV and investigated their characteristicsfor the different types of magnetic holes (linear and rotational holes) both in the magnetosheath and theholes in the solar wind for the year 2011. For the Cassini dataset during 2011, various different shapeand sizes of magnetic hole events have been found. Most (80%) of the MHs appeared within a groupedstructure, while the rest (20%) are found as isolated type holes in the magnetosheath. Among the isolatedMHs, about 30% had "Gaussian shape" and about 40% had a substructure. The scale size for the electrondensity for the isolated holes were on average 50 s in the solar wind, and 75 s (the rotational holes) and120 s (the linear holes) in the magnetosheath. Therefore, I confirmed that the LP can obtain enough datapoints to resolve the magnetic holes structure in the magnetosheath. The Cassini LP data resolution isalso capable to resolve some of the magnetic hole structure in the solar wind.In summary, I confirmed that the Cassini LP continuous data calibrated in this study is capable toinvestigate the different types of magnetic hole structures. Using this calibrated electron data statisticallyfor the large number of Cassini orbit would helpful to further identify the MHs structures in the solar wind and the magnetosheath that can be a key to understand the generation mechanisms of the magneticholes.Lokaliserade strukturer med låg magnetfältstyrkan ses ofta i interplanetära mediet och de kallas ’mag-netiska hål’ (MH) (Turner et al. 1977). Trots et antal observationer av sådana strukturer har observeratsär deras generationsmekanism ännu förstådd. Storleken av strukturerna varierar från ett fåtal till någratusen protongyroradier och även deras kännetecknande inriktningar i magnetfältet varierar. På grund avdetta har olika typer av MH förslagits. Idag klassificerar man MH som ’mirror mode’ och magnetiskaminskningar (Tsurutani et al. 2011). Många studier har undersökt de magnetiska hålens egenskaper,men tyvärr oftast baserats endast på magnetfältsdata. Detta kan bero på strukturernas storlek vid en storsolvindshastighet, där plasmainstrumenten oftast inte har tillräckligt hög tidsupplösning för mätningar,medan magnetfältsinstrumenten kan oftast tillhandahålla data i hög tidsupplösning.Cassini-rymdfarkosten kretsade runt Saturnus i nästan 17 år och erhöll stora mängder data i och näraSaturnus magnetosfär. Langmuir-sonden (LP) ombord Cassini mäter rymdfarkostens potential ochdärmed mäter den elektrontätheten i rymden. Instrumentet fungerar som en slags väderstation för rym-dplasma och möjliggör mätningen av fundamentala plasmaparametrar såsom elektrontäthet, jontäthet,elektrontemperatur och jonmassa i en tät plasmaområdet av nära Saturnus. I den yttre magnetosfären därden plasmatätheten är låg, kan LP mäta rymdfarkosts potential och plasmatätheten. Mätningen, så kallade’sweep mode’ kan skaffades var 10:e minuter. LP:en mäter också i ’kontinuerlig mode’ som möjligenkan mäta plasmatätheten i mer frekventa men den behöver allmän kalibrering. I detta projekt undersökerjag möjligheten att använda LP kontinuerlig data för att studera MH, skapa kalibraring funktion för’kontinuerlig mode’ för att uppskatta plasmatätheten i Saturnus magnetosfär, och även att undersökastorleken och karaktär av plasmatäthetenstrukturen i MH.Jag undersökte först relationen mellan LP ström vid 11V och rymdfarkostens potential i sweep mode data.De härledda funktionerna användes vidare för att uppskatta densiteten med användning av relationenmellan rymdfarkostens potential och elektrontätheten (Morooka et al. 2009). Jag upptäckte också attden kontinuerlig mode funktionen är olika beroende på LP sensors läge i förhållande till solen ochrymdfarkosten. Hur Cassini är inriktad har en stor effekt på relationen och därför beskriva jag fyra olikarelationer för olika inriktningsregioner. Med den kontinuerlig mode funktionen jag härlett, undersöktejag struktur av magnetiska hålen som har listats av Tomas Karlsson på KTH. År 2011 innehåller MH medmycket olika former och storlekar. Den mest (80%) MH identifierades som grupp och resten (20%) varsom isolerade MH i magnetosheath. Av dessa isolerande hål har ca. 30% en Gauss-form och nästan 40%av MH verkar ha en understruktur. Genom att jämföra magfältdatan med elektrontätheten bekräftadejag den allmänna antikorrelationen mellan magnetfältstyrkan och elektrontätheten i MH-strukturerna.Dessutom hittar jag en ökning av elektron β som beräknas med en temperatur av 100 eV för linjära ochroterade MH i den magnetosheath samt MH i solvinden under 2011. Storleken av de isolerade magnetiskahålen är i genomsnitt 50 s i solvinden, 75 s (roterade magnetiska hål) och 120 s (linjära magnetiska hålen)i magnetosheath:en. Därför kan Cassini LP ha tillräcklig många datapoäng för att upplösa struktur avMH i magnetosheath. I solvinden kan LP upplösa en del av relativt stora MH.Sammanfattningsvis kan LP:s kontinuerlig kalibreringen från detta projekt användas för att analyserade olika strukturerna och storlekar av MH. Med denna kalibrerade plasmatäthet data är det möjligt attidentifiera olika MH karaktär i statistiskt för det stora antalet Cassini data. Det skulle vara en stor hjälpför att förstå genereringsmekanismerna av de magnetiska hålen.
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Petrov, Pavel. "Effect of Curvature Squared Corrections to Gravitational Action on Viscosity-to-Entropy Ratio of the Dual Gauge Theory." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10549.
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In this thesis we study the properties of strongly-coupled large-N conformal field theories (CFT’s) using AdS/CFT correspondence. Chapter 1 serves as an introduction. In Chapter 2 we study the shear viscosity of strongly-coupled large-N conformal field theories. We find that it is affected by \(R^2\) corrections to the AdS action and present an example of 4D theory in which the the conjectured universal lower bound on viscosity-to-entropy ratio \(\eta/s > 1/4 \pi\) is violated by 1/N corrections. This fact proves that there is no universal lower bound of \(1/4 \pi\) on viscosity-to-entropy ratio and may be relevant for the studies of QCD quark-gluon plasma for which this ratio is experimentally found to be close to \(1/4 \pi\). In Chapter 3 we study the formation of the electron star in 4D AdS space. We show that in a gravity theory with charged fermions a layer of charged fermion fluid may form at a finite distance from the charged black hole. We show that these “electron stars” are candidate gravity duals for strongly interacting fermion systems at finite density and finite temperature. Entropy density for such systems scales as \(s \sim T^{2/z}\) at low temperatures as expected from IR criticality of electron stars solutions.Physics
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O'Regan, Brian C. "Dye sensitized n-p heterojunctions of titanium dioxide and copper thiocyanate, a new interface for photoinduced charge separation /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/8601.
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Zeybek, Orhan. "Surface studies of magnetic thin films." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367247.
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Khalal, Mehdi Abdelbaki. "Photoionisation multiple des vapeurs métalliques Multi-electron coincidence spectroscopy: Triple Auger decay of Ar 2p and 2s holes 4d -inner-shell ionization of Xe+ ions and subsequent Auger decay." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS552.
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Ce travail de thèse porte sur l’étude expérimentale des processus de photoionisation multiple de vapeurs alcalines par rayonnement synchrotron. Je me suis intéressé particulièrement à la désexcitation par déclin Auger des atomes ionisés en couche interne. Le dispositif expérimental HERMES mis au point par l’équipe est un spectromètre par temps de vol de type bouteille magnétique qui permet de détecter en coïncidence tous les électrons émis lors du processus d’ionisation (photoélectrons) et de relaxation (électrons Auger). Une partie importante de ma thèse a été consacrée à l’améliorer pour permettre également la détection en coïncidence des ions formés. J’ai reconstitué les différentes voies de désexcitation par simple, double et triple Auger qui suivent l’ionisation en couche 2p du potassium (de configuration électronique [Ar] 4s). Les proportions des ions finaux Kn+ (n=2,3 et 4) sont établies et comparées avec les proportions des ions formés par la désexcitation du trou en couche 2p dans l’argon. Cela permet de mettre en évidence le rôle de l’électron 4s lors du processus de désexcitation (spectateur lors de la première étape puis participateur lors de la seconde étape du déclin). Le déclin Auger qui suit l’ionisation et l’excitation de l’électron en couche 3d dans le rubidium est présenté ensuite. Dans la dernière partie de la thèse je présente la double ionisation 4d-15p-1 dans le Xénon que l’on compare à la photoionisation d’un faisceau d’ion Xe+ (expérience MAIA). Le but étant de montrer que ce processus de double ionisation cœur valence permet de simuler le processus d’ionisation en couche interne 4d des ions atomiques Xe+ et le déclin Auger qui s’en suitThe increasing availability of modern x-ray light sources with high tunability, high brightness and narrow photon-energy bandwidth has allowed a deep understanding of the physics behind light and matter interactions. During my PhD, I investigated experimentally different process of photoexcitation and photoionization of rare gas atoms (Argon and Xenon) and alkali metals (Potassium and Rubidium) by the means of synchrotron radiation. Our experimental setup is a 2m long magnetic bottle time-of-flight spectrometer that collect in coincidence almost all the electrons emitted in the 4π solid angle. We investigate the multiple Auger decay of the potassium 2p core holes which has an electronic configuration similar to Ar with an additional 4s valence electron. We show the spectator role of this electron in the decay mechanism and the enhancement of double and triple Auger rates comparing with the Argon 2p holes decay. We also investigated the multiple Auger decay of the rubidium 3d core holes. Finally, we investigated the core valence double photoionization of Xenon atom 4d-15p-1 which is compared with the direct ionization of Xe+ ions (MAIA experiment). We showed that the core valence double photoionization process will populate the same states that the ones populated by the photoionization of the ions. One should note that this process is very weak compared to the 4d inner shell ionization of Xe atom but thanks to the coincidence technique we are able to clearly separate and disentangle each ionization process. Our experiment confirmed the results of MAIA and allowed us to extract the Auger spectra associated with the decay of these Xe+ ions, when ionized in the 4d shell
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Shao, Fangwei Dougherty Dennis A. "DNA-mediated hole and electron transport /." Diss., Pasadena, Calif. : California Institute of Technology, 2008. http://resolver.caltech.edu/CaltechETD:etd-06282007-105808.
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Royo, Valls Miquel. "Theoretical modelling of electrons and holes in semiconductor nanostructures." Doctoral thesis, Universitat Jaume I, 2010. http://hdl.handle.net/10803/669140.
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En esta tesis se utiliza la aproximación de masa efectiva y función envolvente para estudiar teóricamente las propiedades optoelectrónicas de una gran variedad de nanoestructuras semiconductoras, muchas de las cuales son obtenibles en un laboratorio a día de hoy. El primer capítulo de la tesis se centra en el estudio de los efectos derivados de aplicar campos magnéticos externos sobre varias nanoestructuras formadas por anillos cuánticos: dos anillos acoplados lateralmente y verticalmente, y una red periódica bidimensional de anillos. El segundo capítulo constituye la parte más extensa e importante de la tesis y estudia la influencia del entorno dieléctrico sobre las propiedades optoelectrónicas de nanocristales sintetizados mediante técnicas de química coloidal con forma esférica y alargada. Mediante cálculos multipartícula basados en las metodologías DFT y CI, se estudia el efecto del confinamiento dieléctrico sobre nanocristales poblados con un alto número de electrones o con pares electrón hueco. Finalmente, el último capítulo de la tesis se centra en el estudio de los estados multipartícula y las transiciones de fase a lo largo de un proceso en el que un nanocristal esférico es alargado hasta formar una estructura casi unidimensional.
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Mampazhy, Arun S. "Composite quantum well co-existence of electrons and holes /." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2505.
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Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Dept. of Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Murooka, Yoshie. "Parallel electron energy loss spectroscopy of electron hole drilling in calcite." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361611.
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Haines, Andrew. "Electron and hole transport in silicon microstructures." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387602.
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Cáceres, Alejandro. "Electron dynamics in a black hole background." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614691.
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Pingenot, Joseph Albert Ferguson. "Electron and hole spins in quantum dots." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/259.
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As the technology underlying modern electronics advances, it is unlikely that previous rates of power use and computational speed improvement can be maintained. Devices using the spin of an electron or hole, "spintronic" systems, can begin to address these problems, creating new devices which can be used as a continuation and augmentation of existing electronic systems. In addition, spintronic devices could make special use of coherent quantum states, making it feasible to address certain problems which are computationally intractable using classical electronic components. Unlike higher-dimensional nanostructures such as quantum wires and wells, quantum dots allow a single electron or hole to be confined to the dot. Through the spin-orbit effect, the electron and hole g-tensor can be influenced by quantum dot shape and applied electric fields, leading to the possibility of gating a single quantum dot and using a single electron or hole spin for quantum information storage or manipulation.
In this thesis, the spin of electrons and holes in isolated semiconductor quantum dots are investigated in the presence of electric and magnetic fields using realspace numerical 8-band strain-dependent k · p theory. The calculations of electron and hole g-tensors are then used to predict excitonic g-tensors as a function of electric field. These excitonic g-factors are then compared against existing experimental work, and show that in-plane excitonic g-factor dependence on electric field is dominated by the hole g-factor. The dependence of the electron and hole g-tensors on the applied electric field are then used to propose a class of novel quantum dot devices which manipulate the electron or hole spins in either a resonant or a non-resonant mode. Because of the highly parabolic dependence of some components of the hole g-tensor on the applied electric field, a shift in the Larmor frequency and an additional resonance are predicted, with additional shifts and resonances occurring for higher-order dependencies. Spin manipulation times down to 3.9ns for electrons and 180ps for holes are reported using these methods.
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Delgado, Jorge Filipe Mónico. "Kerr black holes with electric charge and scalar hair." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17984.
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Mestrado em FísicaA solução de Kerr [Kerr, 1963] descreve um buraco negro (BN) em rotação no vácuo em Relatividade Geral (RG). Pouco depois da sua descoberta, uma generalização electricamente carregada deste BN foi encontrada [Newman et al., 1965]. No início dos anos 70, poderosos teoremas de unicidade foram estabelecidos em RG, para o vácuo e electro-vácuo, demonstrando que estas são as soluções de BN mais gerais, fisicamente aceitávies, no vácuo ou electro-vácuo. Estas descobertas levaram a duas ideias, amplamente difundidas, mas não demonstradas: 1) BNs não têm \cabelo" [Ruffini and Wheeler, 1971], i:e, mesmo na presença de conteúdos de matéria mais genérica, soluções de BNs devem ser descritas simplesmente pela sua massa, momento angular e outras cargas associadas a uma lei de Gauss; 2) alguns limites específicos na carga e no momento angular observados para estas soluções são genéricos para BNs. Contudo, recentemente foi descoberto que BNs conseguem ter \cabelo" escalar [Herdeiro and Radu, 2014]. Estas soluções, designadas BNs de Kerr com cabelo escalar (BNsKCE), revelaram um mecanismo que permite BNs de Kerr ter cabelo de diferentes campos (escalar, vectorial,...) e com diferentes propriedades. Nesta tese, depois de uma breve revisão sobre soluções padrão de BNs em RG, começaremos por revisitar algumas das técnicas que permitem a construção de BNsKCE, que obtivemos numericamente. Iremos ilustrar o procedimento construindo a conhecida solução de Kerr numericamente, que nos permite testar a exatidão do método. Iremos seguidamente introduzir algumas quantidades físicas de interesse para BNs, relevantes para os limites acima mencionados e ilustrar os seus cálculos num BN de Kerr-Newman e Kerr-Sen. Isto permitir-nos- a estabelecer que estes limites são violados em termos das quantidades calculadas no horizonte para estas soluções. Isto também e o caso dos BNsKCE, no qual, contudo, estes limites podem ser violados, mesmo em termos de quantidades assimpt oticas. Finalmente iremos contruir BNsKCE electricamente carregados e estudar algumas das suas propriedades físicas. Em particular, mostraremos que o factor giromagnético, g, destas soluções obedece a g 6 2.
The Kerr solution [Kerr, 1963] describes a rotating black hole (BH) in vacuum General Relativity (GR). Shortly after its discovery, an electrically charged generalization thereof was found [Newman et al., 1965]. In the 1970s, powerful uniqueness theorems were established in vacuum and electro-vacuum GR, demonstrating these are the most general, physically acceptable, single BH solutions in vacuum or electro-vacuum GR. These ndings led to two widespread beliefs: 1) BHs have \no-hair" [Ru ni and Wheeler, 1971], i:e, even in the presence of more generic matter contents, BH solutions should be described by only their mass, angular momentum and other charges associated to Gauss laws; 2) some particular bounds on the charge and angular momentum observed for these solutions are generic for BHs. Recently, however, it was found that BHs can carry scalar \hair" [Herdeiro and Radu, 2014]. These solutions, called Kerr BHs with scalar hair (KBHsSH), unveiled a mechanism that allows Kerr BHs to carry hair of di erent elds (scalar, vector,...) and with di erent properties. In this thesis, after a brief review of the standard BH solutions in GR, we will start by revisiting some of the techniques that allowed the construction of KBHsSH, that were obtained numerically. We shall illustrate the procedure by constructing the well known Kerr solution numerically, which allows us to test the accuracy of the method. We will then introduce some physical quantities of interest for BHs, relevant for the aforementioned bounds and illustrate their computation in Kerr-Newman and Kerr-Sen BHs. This will allow us to establish that these bounds are violated in terms of horizon quantities for these solutions. This is also the case for KBHsSH, for which, however, these bounds can be violated even in terms of asymptotic quantities. Finally we will construct electrically charged KBHsSH and study some of their physical properties. In particular we will show that the gyromagnetic ratio, g, of these solutions obeys g 6 2.
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Spink, Graham George. "Application of quantum Monte Carlo methods to homogeneous electron and electron-hole systems." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/275725.
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The properties of the macroscopic world around us, and of which we are a part, are largely determined by the low energy, collective behaviour of many interacting particles, including the nuclei and, especially, the electrons present. Although the fundamental laws governing the behaviour of these many-body systems are believed to be known in principle, the practical solution of the equations of quantum mechanics remains a challenging area of research. This thesis is concerned with the application of quantum Monte Carlo methods to two model systems: the spin-polarised homogeneous electron gas, and a hole-doped electron gas. Electronic structure theory is briefly reviewed before discussing in more detail the quantum Monte Carlo methods used in this thesis. A study of the three-dimensional spin-polarised homogeneous electron gas (HEG) is then reported, where the relatively new technique of twist averaging is investigated in detail and accurate energies and pair correlation functions are obtained over densities $r_s = 0.5 – 20$ a.u. and the full range of spin-polarisation, allowing comparison with the Perdew-Zunger interpolation scheme used in local spin density approximation exchange-correlation functionals. Following this, an impurity is added to the electron gas in the form of a positively charged hole, and the interaction is studied. Relaxation energies, pair correlation functions and momentum densities are reported. Trion formation is observed over a range of carrier densities and electron-hole mass ratios in agreement with experiment. Isolated trions are also studied, where the diffusion Monte Carlo method is exact. Methodological innovations developed while carrying out this work are discussed, including a variance reduction technique for twist-averaged calculations and a new trial wave function for impurity-in-HEG calculations.
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Eshghi, Hosein. "Electron and hole transport in GaN and InGaN." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/2237/.
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Edwards, Gerard. "Electron and hole states in low dimensional structures." Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305593.
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Gökcan, Hüseyin. "Magnetotransport of hot electrons and holes in the spin-valve transistor." Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/57119.
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Thangaraj, Mamta Ponammal Shanthi. "Transport measurements in two dimensional electron-hole bilayer devices." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612323.
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Tregurtha, David. "The transport properties of electrons and holes in a silicon quantum well." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636538.
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Semiconductors have revolutionised the field of electronics due to the nature of their readily engineerable bandstructure. Additionally, the study of the 2D charge systems hosted by devices made from these materials has led to the discovery of fundamental physics of these systems. Silicon has been at the forefront of developments in this field owing to its natural abundance, ease of processing and naturally occurring oxide. In this thesis a double gated, metal oxide semiconductor field effect transistor (MOSFET) is used to investigate a number of transport properties of electrons and holes. These include the transport properties of a single layer within a bilayer system, the control of the hole g*m* with the MOSFET gates and probing of the effects of giant valley splitting on the electrons. Bilayer systems are composed of two single, physically separate, layers of charge carriers contained within the same quantum well. Their study has provided insight into carrier interactions between the layers with the potential for use in vertically coupled systems of charges in novel electronic devices. Here the effects of one layer on the I-V characteristics of the other are described. Direct control of the electron or hole spin via the gates of a transistor was first proposed by Datta and Das. Although such a device has yet to be fully realised, control of the g*m* has been demonstrated in a number of materials. Here the control of the hole g*m* is demonstrated on the (001) silicon plane for the first time. Giant valley splitting is an effect whereby the valley degeneracy of the electrons in silicon is lifted. In this thesis, the effects of giant valley splitting is shown to have a similar phenomenological effect on the resistivity of a 2D electron gas as spin splitting does on the same, valley degenerate system.
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Dorin, Catalina I. "Electron paramagnetic resonance and electron nuclear double resonance study of Nb⁵⁺ hole center in CdWO₄." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=745.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains ix, 72 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 40).
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Hu, Yuan Zheng. "Theory of electron-hole pair excitations in semiconductor quantum dots." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185516.
Full textAbstract:
This dissertation considers one- and two-electron-hole-pair excitations in ideally spherical semiconductor quantum dots with infinite or finite confinement potentials. The optical absorption edge of the semiconductor micsrocrystallites is found to be higher than that in the corresponding bulk semiconductor. This blue shift is approximately proportional to 1/R², where R is the radius of the semiconductor microspheres. For small quantum dots with infinite confinement potential, the energies and wave-functions of quantum confined excitons and biexcitons are computed using a numerical matrix diagonalization method. Both numerical matrix digaonalization and perturbative calculations prove that the binding energy of biexcitons is strictly positive regardless of material parameters. A general formula for the optical susceptibility of quantum dots is derived, from which, optical spectra are computed. The theoretical results qualitatively agree with recent experimental observations. Some novel optical properties of quantum dots are revealed by this study, such as the existence of excited biexciton states energetically above the exciton ground state resonance and modified optical nonlinearities. Extending our numerical scheme, we compute the effects of impurities or crystal defects in a simple model. The calculation shows that charge defects or impurities have only a small influence on the optical spectra of quantum dots. The details of the quantum confinement conditions, such as the finite value of the quantum confinement potential and different electron-hole masses inside and outside the dot, are studied within the framework of the variational scheme. Finally, we extend the numerical matrix diagonalization method to investigate the valence band coupling effect in quantum dots by including the Luttinger Hamiltonian. It is found that the concept of heavy- and light-hole has to be modified to describe the hole states in semiconductor quantum dots. Also, the valence band mixing due to spin-orbit interaction changes significantly the optical selection rules and consequently influences the allowed optical excitations in quantum dots.
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Nikolaev, Valentin. "Many-particle correlations in quasi-two-dimensional electron-hole systems." Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248096.
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Cook, Kimberlee S. "The sensation of Sherlock Holmes." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3947.
Full textAbstract:
This thesis examines the Sherlock Holmes stories written by Sir Arthur Conan Doyle and
how they relate to the late-Victorian Sensation Novel. First, a brief introduction to the Sensation
novel is made. It makes a study the character of Sherlock Holmes, his habits, and his cases to
show the sensationalism of his character. It considers the setting of late-Victorian England and
its connections to the world created by Conan Doyle. Finally, it takes into account the
significance of Victorian class structure within the stories. All these come together to confirm
that the Sherlock Holmes stories belonged within the sensation genre.
The research materials include critics such as Philip Davis, author of The Victorians,
Russell Goldfarb, author of Sexual Repression and Victorian Literature, and Steven Marcus,
author of The Other Victorians: A Study of Sexuality and Pornography in Mid-Nineteenth-
Century England. Other sources also include the 1898 Poverty Map created by Charles Booth,
works by Dr. William Acton, and articles from the Penny Illustrated Paper. These sources help
to form conclusions about the Sherlock Holmes stories as sensational stories providing detailed
descriptions and examinations of Holmes' character, sexuality, and lifestyle and how they pertian
to the Sensation genre. The thesis will also take into account different interpretations of Holmes'
character as it has evolved through the 20th and 21st centuries thus far.Thesis (M.A.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of English.
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Zenker, Bernd [Verfasser]. "Electron-hole pair condensation at the semimetal-semiconductor transition / Bernd Zenker." Greifswald : Universitätsbibliothek Greifswald, 2014. http://d-nb.info/1051797799/34.
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Scott, Donald Christopher. "Carrier relaxation and collective phenomena in nonequilibrium semiconductor electron-hole plasmas." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186556.
Full textAbstract:
A quantitative analysis of carrier-carrier scattering for electron-hole semiconductor plasmas is presented. Material parameters appropriate for GaAs are used for all calculations. Calculations are performed using the Boltzmann equation for carrier-carrier scattering. Screening of the Coulomb potential is treated in the fully-dynamical random phase approximation. Results are shown for roomtemperature near-equilibrium and far-from-equilibrium plasmas. Also, the equilibrium zero momentum scattering rates are calculated as a function of temperature (T = 10K to T = 1000K) and density (n = 10¹⁵ cm⁻³ to n = 10¹⁹ cm⁻³). Ultrafast scattering rates (on the order of 10 fs) are found to result for a carrier distribution with vacant low-momentum states. These rates are shown to be associated with the undamping of the acoustic plasmon which influences the scattering through screening of the Coulomb potential. Further analysis of plasmon undamping is presented, showing the conditions necessary for undamping of the acoustic mode. Results from a separate set of calculations, showing the time-evolution of the Wigner distribution for a semiconductor quantum wire, are shown. These numerical calculations were performed using the collisionless quantum Boltzmann equation for the case of a lightly-damped plasmon and an unstable growing plasma mode. Comparison is made with results predicted by the linear theory (Lindhard). Results showing the effects of increasing the field strength beyond the linear regime are also presented.
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Benini, Gabriella. "Studio di celle solari innovative basate su "multiple electron-hole generation"." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8936/.
Full textAbstract:
L’aumento dei consumi energetici e la sempre maggiore attenzione posta al tema ambientale
fanno delle energie alternative una valida alternativa alle fonti , quali carbone e petrolio,che
presentano una elevata generazione di gas serra .
Tra le varie fonti alternative di energia un ruolo preponderante è stato assunto dal solare
fotovoltaico, che dagli anni ’80 ad oggi ha conosciuto un rapido sviluppo sia in termini di
ricerca che di utilizzo su larga scala.
Negli ultimi anni tutti gli studi si stanno concentrando su un nuovo tipo di fotovoltaico,
quello di terza generazione , il cui scopo è quello di ottenere dispositivi che possano
garantire elevate efficienze in modo tale che la tecnologia fotovoltaica sia in grado di
affermarsi definitivamente nel settore dell’energia.
Il presente lavoro di tesi analizza il processo di conversione fotovoltaica ed il
principio di funzionamento delle celle solari . I limiti termodinamici per l'efficienza di
conversione di celle solari a singola giunzione sono stati discussi nella tesi. E' presentata
nella tesi una rassegna delle principali strategie per il superamento dei limiti termodinamici
per l'efficienza di una cella solare a singola giunzione . Sono stati analizzati :
•il processo di rilassamento intrabanda dei nanocristalli ;
•la generazione multipla di eccitoni (MEG)
•il processo di Generazione di eccitoni multipli in nanocristalli di silicio colloidali
(MEG in Si NCs).
Tali risultati rivestono un particolare interesse per lo sviluppo di celle solari innovative , ad
alta efficienza di conversione , utilizzando un materiale facilmente reperibile ed economico
come appunto è il Silicio.
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Marlow, Thomas Peter. "Far-infrared studies of coupled two-dimensional electron and hole gases." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621528.
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Lee, Robert 1962. "Electromagnetic coupling by a wire penetrating a circular aperture in an infinite planar conducting screen." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276731.
Full textAbstract:
We consider the problem of electromagnetic propagation along a wire which passes through an aperture. We begin by formulating an integral equation in terms of the electric field at the aperture. The solution of the integral equation allows us to determine parameters of interest such as the equivalent admittance, the current on the wire, and the electric field. We solve the integral equation using both a zeroth order and method of moments approximation for the aperture field. From this we are able to compute the admittance and current in the frequency domain. We next calculate the current response to a transient pulse excitation. The results show that the screen provides little shielding from pulse penetration along the wire. Finally, we calculate solutions for the electric field. The results are given in several contour plots.
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Wright, Diana Beth 1963. "Electromagnetic coupling by a wire through a cavity-backed circular aperture in an infinite screen." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276823.
Full textAbstract:
The problem of a wire penetrating a circular aperture in an infinite screen and coupling energy into a cavity behind that screen is considered. We formulate an integral equation in terms of the electric field in the aperture. This integral equation is solved using two approximate methods: a zeroth-order approximation valid at low frequencies, and the method of moments. In addition, we introduce an equivalent circuit model to aid in our physical interpretation of the problem. Numerical results for the interior current on the wire and for the equivalent circuit admittance parameters are presented in order to provide a comparison between the two approximations. Inside the cavity, we examine the components of the electric field as a function of position. Finally, the exterior magnetic field far from the aperture is studied as a function of frequency. We examine the relationship between interior resonance features associated with the presence of the cavity and observations of the exterior field.
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Ishitani, Yoshhiro. "Transition processes of electorons and holes in AlGaInP crystals studied by spectroscopic measurements." Kyoto University, 1999. http://hdl.handle.net/2433/77924.
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Wu, Zhenping, and 吴真平. "Studies on thin films and heterojunctions of electron/hole-doped perovskite manganites." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49799307.
Full textAbstract:
Intensive research interests in condensed matter physics have been focused at the strongly correlated electron systems. Most of the efforts were devoted in hole-doped manganites with a double exchange interaction between Mn3+/Mn4+. Recently, tetravalent ions substitution has also stimuli much attention as a supplement for the hole-doping. Such electron-doped manganites may be of great potential for the development of all-manganites devices. Manganites are extremely sensitive to external disturbances, such as magnetic fields, electric fields, currents, mechanical strain, and photo illumination, etc. These extraordinary properties make manganites promising for practical applications. In this thesis, the field modulation on physical properties in electron/hole-doped manganites films and heterojunctions were investigated.
The effects of tetravalent hafnium doping on the structural, transport, and magnetic properties of polycrystalline La1-xHfxMnO3(LHMO) (0.05 ≤x ≤0.3) were studied systematically. A phase diagram was obtained for the first time through magnetization and resistance measurements in a broad temperature range. An abnormal enhancement of magnetization was observed at about 42 K. It was further confirmed that the second magnetic phase MnO2in LHMO gives rise to such a phenomenon. The dynamic magnetic properties of LHMO, such as relaxation and aging processes, were studied, demonstrating a spin-glass state at low temperature accompanied by a ferromagnetic phase.
Heterojunctions composed of n-type SrTiO3-δand p-type GaAs exhibited excellent rectifying behavior from 40K to room temperature. The photocarrier injection effect and a colossal photo-resistance were observed. Strong dependences on both temperature and bias voltage were found as well, which might be under stood by considering the band structure of the formed p-njunction. By employing an ultrathin SrTiO3buffer layer,La0.8Ca0.2MnO3films could be epitaxially grown on GaAs substrates. The heterostructures exhibit good rectifying behavior with a paramagnetic-ferromagnetic transition at ~200K. The variation of diffusion voltage with temperature in these heterostructures could be explained by the effects of the Hund’s rule coupling between the La0.8Ca0.2MnO3and the buffer layer.
The effects of the strain induced by ferroelectric poling on the magnetic and electric properties have been investigated by using 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3(PMN-PT) substrates. The polarization of the PMN-PT crystal reduces the biaxial tensile strain in the formed La0.9Hf0.1MnO3layer.It results in a significant decrease in resistance and an enhancement of the phase transition temperature as well as the magnetization. The impact of the lattice strain on the charge/orbital ordering state was also been studied. The modification of charge/orbital ordering phase by the electric fields and ferroelectric polarization suggested that the unstable states in the manganites are sensitive to the strain.
Heterojunctions of La1-xHfxMnO3/Nb:SrTiO3 were fabricated and investigated under different fields (electric, magnetic and optic). These heterojunctions exhibited excellent rectifying behavior in a wide temperature range. Their properties could be significantly modulated by magnetic fields. Prominent photovoltaic effect was also observed in the formed junctions.published_or_final_version
Physics
Doctoral
Doctor of Philosophy
35
Martin, Patrick Michael. "Magnetospectroscopy of electron and hole tunnelling in (AlGa) as resonant tunnelling structures." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363614.
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Brosh, Boaz. "Transport properties of electron and hole gases in weakly 1D modulated potentials." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624174.
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Vampa, Giulio. "Role of Electron-Hole Recollisions in High Harmonic Generation from Bulk Crystals." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34935.
Full textAbstract:
When intense laser pulses interact with an atomic or solid target, high order harmonics of the fundamental laser frequency are generated. In the case of atoms, this highly nonlinear optical process is initiated by ionization and terminated by the
energetic recollision and recombination of the ionized electron with its correlated
ion. In this thesis I demonstrate, both theoretically and experimentally, that high
harmonics from bulk crystals can originate from the recollision of electrons with
their associated holes, similarly to the atomic case, but where ionization is replaced
by excitation of electron-hole pairs that accelerate within the material. This model
is first derived from a quantum-mechanical theory of the solid-laser interaction, and
then confirmed experimentally in ZnO and Si crystals. Despite the link I establish
between high harmonic generation in solids and gases, there are notable dissimilarities. These include: a generalized motion of electrons and holes in their respective bands and its consequences, a more prominent role of dephasing and enhanced sensitivity to perturbing fields. These aspects are investigated throughout this thesis. Finally, I develop a method that exploits the recollision mechanism to reconstruct the momentum-dependent band structure of solids.
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Mejergren, Henrik. "Multipoint Measurements of Magnetic Holes in the Pristine Solar Wind." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290371.
Full textAbstract:
Satellite data from the Cluster satellites have been used to find and evaluate structures in the pristine solar wind, referred to as magnetic holes. By using multipoint measurements, size and orientation-estimates are established. Other characteristics of interest are also examined, such as velocity, temperature, density, and pressure. The results show that the magnetic holes vary in both shape and size, but with a median difference between the minor and major axis by a factor of five. Most of the events also show increases in both density and ion temperature compared to background values. Comparisons have been made with studies of similar structures downstream of the bow shock referred to as plasmoids which show an even more flattened shape in the direction of the plasma velocity. This study did however not find any such correlations when looking at projections in the GSE-coordinate system. This could suggest that these structures are being compressed in the direction of the velocity as they travel past the bow shock, most likely due to the drastic decrease in velocity. Furthermore, no distinct correlation is found between the size of the MH and the drop of magnetic field strength.Satellitdata från Cluster-satelliterna har använts för att hitta och utvärdera strukturer i den orörda solvinden, kallade magnetiska hål. Genom att använda flerpunktsmätningar fastställs storlek och orienteringsuppskattningar av dessa. Även andra egenskaper av intresse undersöks, såsom hastighet, temperatur, densitet, och tryck. Resultaten visar att de magnetiska hålen varierar både i storlek och form, med en storaxel som är cirka fem gånger större än lillaxeln om man tittar på medianvärdet. De flesta magnetiska hål visar ökningar i både densitet och jontemperatur jämfört med bakgrundsvärden. Jämförelser har gjorts med studier av liknande strukturer, nedströms bågchocken som kallas plasmoider. Dessa visar en ännu mer tillplattad form, i plasmahastighetens riktning. Denna studie hittade dock inga sådana korrelationer när man tittade på formen i GSE-koordinater. Detta kan tyda på att dessa strukturer komprimeras i hastighetens riktning när de färdas förbi bågchocken, troligtvis på grund av den drastiska minskningen av hastigheten. Studien visar inte heller någon tydlig korrelation mellan storleken på hålen och dess minskning av magnetfältstyrkan.
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Javed, Rehman Yasin. "Processing and magneto-transport studies of InAs/GaSb low dimensional structures." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343523.
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OLBRIGHT, GREGORY RICHARD. "FEMTOSECOND DYNAMICS AND NONLINEAR EFFECTS OF ELECTRON-HOLE PLASMA IN SEMICONDUCTOR DOPED GLASSES." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184091.
Full textAbstract:
The following is a comprehensive study of transient and steady-state nonlinear optical properties of semiconductor microcrystals embedded in a glass matrix (semiconductor doped glass). Transient thermal effects which give rise to longitudinal excitation discontinuities (i.e., kinks) that arise from partial sample switching in increasing absorption optical bistability are observed in a doped glass. The transient thermal effects occur on time scales of a few hundred milliseconds. Femtosecond and nanosecond laser pulses are employed to measure time-resolved and steady-state transmission and differential transmission spectra. The measured spectra reveal several beautiful effects which are attributed to the many-particle effects of electron-hole plasma. The spectra reveal: bandgap renormalization, broadening of the tail states and screening of the continuum states, state filling (spectral hole burning), thermalization of nonthermal carrier population distributions, band filling due to carrier relaxation of the thermal and nonthermal distributions, direct electron-hole recombination and long lived (>>100 ps) tail states which are attributed to electron trapping. Absorption edge dynamics discussed in this dissertation span 15 orders of magnitude.
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Galaktionov, Evgeniy A. "Transport and thermodynamic properties of low-density two-dimensional electron and hole systems." Thesis, University of Exeter, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439126.
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Keogh, James Andrew Christian. "Fabrication and measurement of closely-spaced electron-hole bilayers in GaAs/AlGaAs heterostructures." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615273.
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Pattanasattayavong, Pichaya. "Solution-processable hole-transporting inorganic semiconductors for electronic applications." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24775.
Full textAbstract:
This thesis presents the development of solution-processable hole-transporting inorganic semiconductors for electronic applications. As the improvement of electron-transporting oxides, such as ZnO, In2O3, and SnO2, has continued to advance, the progress on the hole-transporting counterparts is still largely lagging behind. Copper(I) oxide (Cu2O) is one of a handful oxide materials that shows hole transport. This thesis shows the first demonstration of p-channel TFTs from Cu2O thin films processed from the spray pyrolysis technique. The field-effect hole mobility (μ_FE) is in the range of 10^-4 to 10^-3 cm^2/(V.s) while the on-to-off channel current ratio (I_D^on-off) is on the order of 10^3. The work presented here emphasises the versatility of the spray pyrolysis, which has previously been employed to successfully produce n-type oxides and dielectrics. Another copper(I)-based inorganic compound, copper(I) thiocyanate (CuSCN), has a unique combination of good hole-transporting characteristics and excellent optical transparency. This thesis presents extensive characterisation results of CuSCN thin films from their chemical, electronic, optical, morphological, to structural properties and demonstrates, for the first time, p-channel TFTs with a truly transparent active layer based on a solution-processed wide-band-gap inorganic semiconductor. μ_FE in the range of 0.01-0.1 cm^2/(V.s) has been achieved whereas I_D^on-off is on the order of 10^4. A p-channel unipolar voltage inverter has also been constructed from CuSCN TFTs, showing the possibility of realising transparent electronics. CuSCN-based TFTs are also studied in more details by analysing their transfer characteristics for the distribution of localised states and examining their temperature dependence for the hole transport modes. Furthermore, due to its novel electronic and optical properties, CuSCN is also offered as a replacement of PEDOT:PSS as a hole-transporting layer in bulk-heterojunction organic photovoltaics (OPVs) and organic light-emitting diodes (OLEDs). Owing to its superior optical transparency, CuSCN-based solar cells consistently exhibit higher power conversion efficiency (PCE) than PEDOT:PSS-based cells, especially in the case of cells employing active layers that absorb light in the near-infrared spectral range. Specifically, cells based on PDPP-2T-TT:PC71BM show PCE of ~8% with CuSCN HTL compared to ~6.2% with PEDOT:PSS HTL. In addition, the energy levels of CuSCN lead to a lower hole injection barrier as well as effective electron blocking property, yielding OLEDs with a low turn-on voltage and low leakage current. OLEDs employing an active layer of (PPy)2Ir(acac) in 26DCzPy:TCTA with CuSCN HTL show higher values of highest achievable efficacies (51 cd/A and 55 lm/W at 1 cd/m^2) compared to those with PEDOT:PSS HTL (38 cd/A at 2142 cd/m^2 and 14 lm/W at 1710 cd/m^2).
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Raghavan, Bharadwaj Veera. "Stress concentrations due to countersunk holes in adhesively bonded bi-layered aluminum subjected to tensile loading." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/5027.
Full textAbstract:
The adhesively bonded layered aluminum is used in aircraft structures to avoid knife edge situations when flush head fasteners are used with minimum gage skins. Due to the countersunk hole and adhesive bonding, stress flow becomes more complicated. Extensive knowledge of the different parameters that affect the behavior of the bonded joints with countersunk holes is essential for dependable and effective design. A 3-D finite element model was used to estimate the location and magnitude of stress concentration under remote tension for the aforementioned problem.
The influence of the various parameters on stress concentration was investigated for a counter sunk angle of 100º. Different parameters such as ratio of young‟s modulus of adhesive to aluminum, position of adhesive layer, countersunk sunk depths, ratio of thickness to radius and ratio of width to radius have been addressed in this study.
The stress flow varies significantly when the plates are filled with fasteners of different pre-tension loads. Also the effects of pre-tension loading were compared for the cases of open hole and fastener filled hole without pre-tension for bonded, monolithic and straight shank hole. The results obtained from the finite element analysis for the monolithic cases have been validated against those reported in literature.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering.
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Moeketsi, Daniel Mojalefa. "Modelling of galactic and jovian electrons in the heliosphere / Daniel M. Moeketsi." Thesis, North-West University, 2004. http://hdl.handle.net/10394/194.
Full textAbstract:
A three-dimensional (3D) steady-state electron modulation model based on Parker (1965) transport
equation is applied to study the modelling of – 7 MeV galactic and Jovian electrons in the inner
heliosphere. The latter is produced within Jupiter's magnetosphere which is situated at - 5 AU in the
ecliptic plane. The heliospheric propagation of these particles is mainly described by the heliospheric
diffusion tensor. Some elements of the tensor, such as the diffusion coefficient in the azimuthal direction,
which were neglected in the previous two-dimensional modulation studies are investigated to account for
the three-dimensional transport of Jovian electrons. Different anisotropic solar wind speed profiles that
could represent solar minimum conditions were modelled and their effects were illustrated by computing
the distribution of 7 MeV Jovian electrons in the equatorial regions. In particular, the electron intensity
time-profile along the Ulysses spacecraft trajectory was calculated for these speed profiles and compared
to the 3-10 MeV electron flux observed by the Kiel Electron Telescope (KET) on board the Ulysses
spacecraft from launch (1990) up to end of its first out-of-ecliptic orbit (2000). It was found that the
model solution computed with the solar wind profile previously assumed for typical solar minimum
conditions produced good compatibility with observations up to 1998. After 1998 all model solutions
deviated completely from the observations. In this study, as a further attempt to model KET observations
more realistically, a new relation is established between the latitudinal dependence of the solar wind
speed and the perpendicular polar diffusion. Based on this relation, a transition of an average solar wind
speed from solar minimum conditions to intermediate solar activity and to solar maximum conditions
was modelled based on the assumption of the time-evolution of large polar coronal holes and were
correlated to different scenarios of the enhancement of perpendicular polar diffusion. Effects of these
scenarios were illustrated, as a series of steady-state solutions, on the computed 7 MeV Jovian and
galactic electrons in comparison with the 3-10 MeV electron observed by the KET instrument from the
period 1998 up to the end of 2003. Subsequent effects of these scenarios were also shown on electron
modulation in general. It was found that this approach improved modelling of the post-1998 discrepancy
between the model and KET observations but it also suggested the need for a time-dependent 3D
electron modulation model to describe modulation during moderate to extreme solar maximum
conditions.Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.
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Stenta, Caterina. "Novel electron acceptors and new solution processed hole blocking layer for organic solar cells." Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/667292.
Full textAbstract:
La utilització de materials orgànics per a la fabricació de cèl·lules solars és una de les alternatives considerades actualment per a reduir els costos de fabricació de sistemes fotovoltaics.
Els materials orgànics tenen coeficients d’absorció elevats que permeten la utilització de capes primes i tècniques de fabricació de baix cost.
L’objectiu d’aquesta tesi ha estat contribuir a la millora de les cèl·lules solars orgàniques d’heterounió massiva, mitjançant la incorporació de nous materials acceptors i donadors d’electrons, així com de capes de blocatge de forats depositades a partir de solucions.
S’ha dut a terme l’estudi dels efectes de les capes transportadores d’electrons i forats en termes d’eficiència i de degradació dels dispositius fotovoltaics. S’han estudiat i fabricat capes de blocatge de forats amb bathocuproïna (BCP) depositada a través d’una tecnologia de solucions com a substitució del calci.El empleo de materiales orgánicos en la fabricación de celulas solares es una de las alternativas actualmente consideradas para reducir los costes de fabricación de los sistemas fotovoltaicos. Los materiales organicos tienen coeficientes de absorpción elevados, permitiendo el uso de capas finas y técnicas de fabricación de bajo coste. El objectivo de esta tesis ha sido contribuir en la mejora de las células solares orgánicas de heterounión masiva, mediante la incorporación de nuevos materiales aceptores de la familia de los PDI, y de capas bloqueadoras de huecos depositadas a partir de soluciones. Se han estudiado los efectos de las capas transportadoras de electrones y huecos en términos de eficiencia y degradación de dispositivos fotovoltaicos. Se han fabricado capas bloqueadoras de huecos con bathocuproine (BCP) depositada a través de una tecnología de soluciones como sustituyente del Calcio. Se han estudiato y caracterizado las propriedades morfologicas y optoelectronicas de celulas solares con las estructuras ITO/PEDOT:PSS/PTB7:PDI/Ca/Ag y ITO/PEDOT:PSS/PTB7:PCBM/BCP/Ag. Se ha llevado a cabo una caracterización de las propiedades morfológicas y fotofísicas de los dispositivos fotovoltaicos fabricados a través de varios métodos de investigación, entre los cuales medidas J-V, EQE, Difracción de rayos X, medidas espectroscopia UV-Vis, medidas de movilidad de portadores, medidas de extracción de carga y foto-voltaje transitorio, AFM y medidas de ángulo de contacto.
The search for low cost photovoltaics has led to the use of organic materials as possible candidates to substitute silicon based solar devices. Organic materials have high absorption coefficients, allowing the use of thin layers and low cost solution phase manufacturing techniques. The objective of this thesis has been to contribute to the improvement of bulk-heterojunction organic solar cells through the incorporation of new acceptor materials of the PDI family and of a film layer of Bathocuproine (BCP) as hole blocking layer. The BCP layer was spin coated from a dilute toluene/methanol solution directly on top of the active layer. The morphological, optoelectronic properties of solar cells with the following structures have been studied and characterized: ITO / PEDOT: PSS / PTB7: PDI / Ca / Ag and ITO / PEDOT: PSS / PTB7: PCBM / BCP / Ag. For this purpose various characterization methods has been carried out, including JV measurements, EQE, X-ray diffraction, UV-Vis spectroscopy, carrier mobility measurements , charge extraction and transient photo-voltage measurements and AFM.
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Barceló, Gisbert Irene. "Study of different electron and hole transporting materials for quantum dot-sensitized solar cells." Doctoral thesis, Universidad de Alicante, 2015. http://hdl.handle.net/10045/50105.
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El Sol proporciona a la Tierra una enorme cantidad de energía limpia. Sin embargo, para que la energía solar represente una parte importante del sistema energético mundial, se necesitan dispositivos fotovoltaicos más económicos y eficientes que los que se utilizan actualmente. Recientemente ha aparecido un nuevo diseño de célula solar, la célula solar sensibilizada de puntos cuánticos (cuyas siglas en inglés son QDSSCs), capaz de sobrepasar teóricamente el límite de Shockley-Queisser (al cual obedecen las células de primera y segunda generación). Sin embargo, el rendimiento de estos dispositivos es todavía bajo y su coste se ha visto algunas veces comprometido por el uso de ciertos materiales y procedimientos. Esta tesis trata de arrojar algo de luz sobre ciertos aspectos fundamentales que gobiernan el funcionamiento de estos dispositivos: el mecanismo de crecimiento y el modo de anclaje del elemento absorbente de luz sobre el aceptor de electrones/huecos, el empleo de capas intermedias para prevenir los procesos de recombinación en las diferentes interfases, la dinámica de los portadores de carga en el sistema donador-aceptor, etc. Además, se han investigado materiales de bajo coste y conceptos de célula muy poco explorados. Todo con el último propósito de allanar el camino para la obtención de QDSSCs económicas, estables y competitivas.
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Sakhel, Roger Raji. "Laser-induced electron-hole correlations in a quantum dot with an internal tunneling barrier /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486462702465019.
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Hazama, Yuji. "Excitonic fine structure and nonequilibrium phase transition of the electron-hole system in diamond." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199093.
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Liu, Shuhao. "Electronic Transport in Functional Materials and Two-Dimensional Hole System." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1522893320666086.
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