Дисертації з теми "Electron phases"
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Ghaemi, Mohammadi Pouyan. "Phases and phase transitions of strongly correlated electron systems." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45456.
Повний текст джерелаIncludes bibliographical references (leaves 169-174).
Different experiments on strongly correlated materials have shown phenomena which are not consistent with our conventional understandings. We still do not have a general framework to explain these properties. Developing such a general framework is much beyond the scope of this thesis, but here we try to address some of challenges in simpler models that are more tractable. In correlated metals it appears as strong correlations have different effect on different parts of fermi surface. Perhaps most striking example of this is normal state of optimally doped cuprates; the quasiparticle peaks on the nominal fermi surface do not appear uniformly. We try to track such phenomena in heavy fermion systems, which are correlated fermi liquids. In these systems, a lattice of localized electrons in f or d orbitals is coupled to the conduction electrons through an antiferromagnetic coupling. Singlets are formed between localized and conduction electrons. This singlet naturally have non-zero internal angular momentum. This nontrivial structure leads to anisotropic effect of strong correlations. Internal structure of Kondo singlet can also lead to quantum Hall effect in Kondo insulator, and formation of isolated points on the fermi surface with fractionalized quasiparticles. In the second part we study a phase transition in Heisenberg model between two insulating phases, Neel ordered and certain spin liquid state, popular in theories of the cuprates. The existence of such a transition has a number of interesting implications for spin liquid based approaches to the underdoped cuprates and clarifies existing ideas for incorporating antiferromagnetic long range order into such a spin liquid based approach. This transition might also be enlightening, despite fundamental differences, for the heavy fermion critical points where a second order transition between the heavy fermion phase and a metallic phase with magnetic antiferromagnetic order is observed.
by Pouyan Ghaemi Mohammadi.
Ph.D.
Boullay, P. "Caractérisations structurales, phases modulées et transitions de phases: le cas des phases d'Aurivillius." Habilitation à diriger des recherches, Université de Caen, 2008. http://tel.archives-ouvertes.fr/tel-00522718.
Повний текст джерелаSahebsara, Peyman. "Competing phases in strongly correlated electron systems with frustration." Thèse, Université de Sherbrooke, 2008. http://savoirs.usherbrooke.ca/handle/11143/5104.
Повний текст джерелаLiu, Zhongsheng. "Magnetic MAX phases: Itinerant electron magnetism of pure and Mn-doped Cr-based MAX phases." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199312.
Повний текст джерелаMross, David Fabian. "Exotic phases and quantum criticality in gapless correlated electron systems." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84394.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 213-219).
In this thesis, I theoretically studied exotic phases of matter than arise due to strong interactions between electrons in three different scenarios. Firstly, at a stripe melting phase transition, which may be relevant for the high temperature superconductors, where we propose a specific type of transition which produces critical exponents agreeing with neutron scattering experiments on LSCO. Secondly, for a Pomeranchuk transition where an electronic nematic order parameter develops we present a controlled expansion within which the physics of such a transition, and of the related problem of fermions coupled to a gauge field, can be addressed. Thirdly, in a quantum spin liquid phase that is likely to be realized in certain organic Mott insulators. Here we show how such a phase can be accessed from a low energy description of a metal, without resorting to slave-particle constructions. Methodologically, the work in this thesis relies on field theoretical methods such as the renormalization group, the large-N and related expansions, dualities, bosonization and slave-particle constructions.
by David Fabian Mross.
Ph.D.
Manini, Nicola. "Electron-Vibron Coupling in Charged Fullerene, Berry Phases and Superconductivity." Doctoral thesis, SISSA, 1996. http://hdl.handle.net/20.500.11767/3874.
Повний текст джерелаAndrusenko, Iryna [Verfasser]. "Structural characterization of intermediate and metastable phases by electron microscopy / Iryna Andrusenko." Mainz : Universitätsbibliothek Mainz, 2015. http://d-nb.info/1068120258/34.
Повний текст джерелаTeo, Chi-yan Jeffrey. "Geometric phase and spin transport in quantum systems." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38226571.
Повний текст джерелаTeo, Chi-yan Jeffrey, and 張智仁. "Geometric phase and spin transport in quantum systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38226571.
Повний текст джерелаJohnson, Lars. "Nanoindentation in situ a Transmission Electron Microscope." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8333.
Повний текст джерелаThe technique of Nanoindentation in situ Transmission Electron Microscope has been implemented on a Philips CM20. Indentations have been performed on Si and Sapphire (α-Al2O3) cut from wafers; Cr/Sc multilayers and Ti3SiC2 thin films. Different sample geometries and preparation methods have been evaluated. Both conventional ion and Focused Ion Beam milling were used, with different ways of protecting the sample during milling. Observations were made of bending and fracture of samples, dislocation nucleation and dislocation movement. Basal slip was observed upon unloading in Sapphire. Dislocation movement constricted along the basal planes were observed in Ti3SiC2. Post indentation electron microscopy revealed kink formation in Ti3SiC2 and layer rotation and slip across layers in Cr/Sc multilayer stacks. Limitations of the technique are presented and discussed.
Muggerud, Astrid Marie Flattum. "Transmission electron microscopy studies of dispersoids and constituent phases in Al-Mn-Fe-Si alloys." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26385.
Повний текст джерелаAluminiumslegeringer Produksjon av aluminium er en energikrevende prosess. Norges store vannkraftressurser gjør produksjon av aluminium i Norge både bærekraftig og lønnsom. Ved å tilsette legeringselementer kan materialegenskapene til aluminium forandres. Dette gir aluminiumslegeringer en rekke bruksområder. Gode egenskaper er høy styrke, lav vekt, god termisk og elektrisk ledningsvevene, høy formbarhet og lav vekt. Lav vekt er fordelaktig i et miljøperspektiv for eksempel i transportsektoren, da drivstofforbruket kan bli redusert. Aluminium er resirkulerbart, og bare 5% av energien som brukes i primær aluminiumsproduksjon trengs for å resirkulere aluminium. Den kjemiske sammensetningen av legeringene endres når materialet resirkuleres, og dette endrer materialegenskapene og mikrostrukturen til materialet. Man må derfor forsøke å forstå disse endringene og forutse hvordan material egenskapene vil endres ved resirkulering. 3xxx aluminium legeringer brukes blant annet til varmevekslere, bygningsprodukter og matinnpakning. I disse legeringene tilsettes jern, mangan og silisium. Konstituente faser blir dannet under størkningen av aluminium, og dispersoidene felles ut under homogenisering. Disse fasene er veldig viktige fordi de påvirker og bestemmer hvordan materialegenskapene endrer seg i legeringene. I denne avhandlingen har dispersoide faser og konstituente faser blitt studert med Transmisjonselektronmikroskop teknikker som hovedverktøy. Hovedfokuset for avhandlingen har vært å studere α-Al(Fe,Mn)Si dispersoider. Hvordan disse dispersoidene påvirker hardhet og spenninger i materialet ble systematisk studert. Det ble funnet en hardhetseffekt i legeringene med et høyt Si og Mn innhold, som er viktig for noen anvendelser. En metodologi for å koble tomografi og diffraksjonstudier av α-Al(Fe,Mn)Si dispersoider ble også utviklet for å kunne gi et komplett bilde av dispersoidenes morfologi, fasetter og orientering. α-Al(Fe,Mn)Si dispersoide fasen er en kubisk ikosaeder kvasi krystallinsk approksimasjon fase. Å undersøke slike kvasikrystallinske approksimasjons faser er viktig for å forså kvasikrystaller. Diffraksjonstudier bekreftet og verifiserte orienteringen av α-Al(Fe,Mn)Si dispersoidene i aluminium. En forklaringsmodell som knyttet kvasikrystallenes orientering og dispersoideorienteringen ble laget.
Jung, Younjoon 1971. "Dynamics and spectra in condensed phases : single molecule spectroscopy, electron transfer, and excitation energy transfer." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8055.
Повний текст джерелаVita.
Includes bibliographical references.
In this thesis, several problems regarding dynamics and spectra in condensed phases are theoretically analyzed via analytical models. The thesis consists of four main topics. First, a theoretical description of single molecule spectroscopy is presented in order to study time-dependent fluctuations of single molecule spectra in a dynamic environment. In particular, the photon counting statistics is investigated for a single molecule undergoing a generic type of spectral diffusion process. An exact analytical solution is found for this case, and various physical limits are analyzed. Second, motivated by recent experimental observations of anomalous spectral fluctuations in quantum dot systems, both the lineshape phenomenon and the photon counting statistics are explored when spectral fluctuations are characterized by power-law statistics, for which there is no finite timescale. Unique features of the power-law statistics are demonstrated in spectral properties of those systems. Third, a spectral analysis method is developed for the non-adiabatic electron transfer reactions, which allows a unified treatment of diverse kinetic regimes in the electron transfer process. The method is applied to electron transfer reactions in mixed-valence systems in order to explore the possibility of electronic coherence. Finally, effects of the nonequilibrium bath relaxation on the excitation energy transfer process are investigated by generalizing the Forster-Dexter theory of excitation energy transfer to the case of the nonstationary bath relaxation.
by YounJoon Jung.
Ph.D.
Klironomos, Filippos. "Tunneling between two dimensional electron systems in a high magnetic field and crystalline phases of a two dimensional electron system in a magnetic field." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0009801.
Повний текст джерелаHu, Wenjun. "Unconventional Phases in Doped or Frustrated Quantum Antiferromagnets: a Systematic QMC Study." Doctoral thesis, SISSA, 2013. http://hdl.handle.net/20.500.11767/4814.
Повний текст джерелаSnoeck, Etienne. "Phases incommensurables de la berlinite et du quartz imagees par microscopie electronique." Toulouse 3, 1986. http://www.theses.fr/1986TOU30067.
Повний текст джерелаTsang, Wai-kan, and 曾衛勤. "Determine the atomic structure of a surface with mixed structure phases by using LEED Patterson function." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30497115.
Повний текст джерелаIvanov, Victor V. "Separation de phases et interaction electron-phonon dans yba#2 cu#3 o#7## : une etude par spectroscopie raman." Nantes, 1998. http://www.theses.fr/1998NANT2023.
Повний текст джерелаMagné, Damien. "Synthèse et structure électronique de phases MAX et MXènes." Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2284/document.
Повний текст джерелаThe aim of this work is at first to study the electronic structure of bidimensional titanium carbide systems, belonging to the MXene family and also to synthesize thin films of such new materials to characterize their properties. The study of the electronic structure has been performed for the Ti3C2T2 MXene with a special attention to the T surface groups by using a combination of electron energy loss spectroscopy and ab initio calculations. This study, focused on both valence and core electrons excitations, enabled the identification of the surface group localization, their influence on the MXene electronic structure as well as their chemical nature. The limits of our TEM-based study is also discussed in view of irradiation phenomena which induce the loss of hydrogen atoms. The synthesis of a MXene thin film requires, beforehand, that of a MAX phase thin film: we opted for Ti2AlC, the precursor for the Ti2C MXene. The MAX phase thin film synthesis was carried out by ex-situ annealing of a multilayer layers. X-ray diffraction experiments and cross-sectional transmission electron microscopy observations show that a highly textured Ti2AlC thin film is obtained above 600°C after the formation, at 400°C, of a metastable solid solution. Finally, by using the same process for V2AlC, we demonstrate that the initial phase orientation plays a key role for the texture of the thin film so obtained
Niang, Aliou. "Contribution à l’étude de la précipitation des phases intermétalliques dans l’alliage 718." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0008/document.
Повний текст джерелаMany structural alloys are strengthened by the presence of precipitates in the grains or at grain boundaries. Nickel based superalloys often present an austenitic γ matrix in which ordered intermetallic phases precipitate. In the alloy Inconel 718, one can find γ’ L12 cubic ordered precipitates together with the compound Ni3Nb in its metastable form γ" (D022 - tetragonal) or the stable phase δ (D0a - orthorhombic). The incidence of those precipitates on macroscopic properties of the alloy 718 is well known and widely used in industrial applications. However the mechanisms responsible for the precipitation and transformation of these phases are not fully understood, which motivated the present study. The alloy microstructure has been observed by optical microscopy (OM) and electron microscopy (scanning and transmission, SEM and TEM) in the as received state as well as after heat treatment (isothermal and anisothermal). Differential thermal analysis (DTA) was used to determine the precipitation and dissolution temperatures of the phases γ', γ" and δ. Various precipitation microstructures were obtained by heat treatments based on available TTT diagrams. Some of the structural defects present in γ" and δ precipitates have been characterised by lattice imaging TEM observations. It is shown that stacking faults in γ’’ phase can act as a seed for the germination of . The structure of the δ/γ interface and the orientation defects in δ lamellae suggest that the growth of δ phase occurs directly from the matrix (and not by transformation of the γ’’ phase)
Gonzalez, Vallejo Isabel. "Study of the structural dynamics of phase transitions using time resolved electron and X-ray diffraction." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS496.
Повний текст джерелаThe application of an external perturbation in certain materials (such as temperature, pressure or light) often gives rise to the emergence of new macroscopic properties with their origin at the atomic level. Therefore, a detailed study of the atomic dynamics becomes essential to the understanding of processes such as chemical transformations or phase transitions. In the particular case of structural phase transitions, the symmetry of the crystal undergoes a transformation between two different states at a given critical value. The typical time scales of the structural dynamics occur on the order of few hundreds of femtoseconds to several picoseconds. The development of femtosecond laser pulses has enabled scientists to access the required time scales to explore the ultrafast dynamics of the lattice structure in the relevant time scales. More precisely, time-resolved diffraction has proven to be an ideal technique to track and unveil the out-of-equilibrium pathways followed by the lattice after a short laser pulse.This thesis presents experimental studies performed by time-resolved electron and X-ray diffraction techniques on two different structural phase transitions. In a first part, we demonstrate the capabilities of the ultrafast electron diffraction (UED) experimental setup developed at Laboratoire d’Optique Apliquée. Our UED experimental results performed on high quality single crystal samples are presented along with a quantitative study of the implications of dynamical diffraction effects in UED experiments. In a second part, we present a set of pump-probe electron diffraction experiments performed on GdTe₃, a compound belonging to the rare-earth Tritellurides family which presents a charge density wave state. The arrival of an optical excitation triggers the phase transition non-thermally with the out-of-equilibrium relaxation dynamics of the charge density wave state characterized by slowing down that increases with incident fluence as well as with initial sample temperature. These results shed more light on current controversial interpretations involving the emergence of photoinduced topological defects. In a third part, we present time resolved X-ray diffraction experiments performed at CRISTAL beamline at SOLEIL synchrotron. In this case we have studied the A15 compound Nb₃Sn, which displays a displacive phase transition evolving from cubic to tetragonal symmetry at thermal equilibrium. Our pump-probe results present evidence of a different lattice response with respect to the thermal equilibrium transition, encouragingf uture investigations on the dynamics of this material
Le, Calloch Maxime. "Study of the single electron charge signals in the XENON100 direct Dark Matter search experiment." Nantes, 2014. https://archive.bu.univ-nantes.fr/pollux/show/show?id=f4984b95-6904-4ff8-bcd6-50f3768ac873.
Повний текст джерелаFrom the observation of the Universe, it has been demonstrated that the mass associated to visible matter represents only few percent of its energetic budget, while the remaining part is composed by dark energy, responsible to the cosmological expansion, and by some hidden matter, the dark matter. The likeliest particles family used to describe this dark matter is called WIMP (Weakly Interacting Massive Particles). That kind of particles could be directly detected by measuring nuclear recoil during an elastic scattering inside a scintillating material. For this, the XENON Collaboration has developed a detector consisting in a time projection chamber (TPC) using xenon dual phase (liquid and gas) detector, and placed underground. The different ionization density of nuclear recoils induced by WIMPs, and electronic recoils induced by β particles or g rays background source, leads to different ratio between both signals, in the liquid and in the gas phase, and is used to discriminate WIMPs from background. A good knowledge of the ionization signal is strongly required for such a detector. In this context, the XENON100 response to single electron charge signals is investigated. They correspond to very tiny signals emitted in the gas phase by one or few electrons extracted in time coincidence. Thanks to this analysis, an innovative method to establish the extraction yield of electrons from the liquid to the gas phase has been drawn, allowing to explore a key information to reject electronic recoils from nuclear ones
Ben, Romdhane Ferdaous. "Synthèse et caractérisation de nouvelles phases bidimensionnelles par microscopie électronique in-situ." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE001/document.
Повний текст джерелаThe aim of this thesis is the synthesis and characterization of new two-dimensional phases in an in-situ transmission electron microscopy experiment. These studies concerned the nucleation and growth of three deferent materials: quasi-two-dimensional silica (SiO2), the smallest possible carbon cages with the size of C20, and two-dimensional chalcocite (β-Cu2S). The characterization of these structures has been performed using high resolution imaging (HRTEM) and electron energy-loss spectroscopy (EELS). The first part of this thesis is devoted to the study of the nucleation and growth of an ordered or disordered 2D crystalline phase of silica on different substrates (Co, Ru, Fe) and a 1D silica phase grown at atomic steps of a metal surface. The second part illustrates the in-situ growth of the smallest possible carbon cages with a diameter of about 0.36 nm on catalytically active metal surfaces such as Co, Fe, or Ru. The last part is devoted to the growth of the thinnest stable layer of β-Cu2S on a graphene surface. All these studies were accompanied by image simulations
Haddad, Noël. "Étude des propriétés diélectriques des phases Mn+1AXn par spectroscopie de pertes d'énergies des électrons." Paris 11, 2009. http://www.theses.fr/2009PA112349.
Повний текст джерелаThe MAX phases are ternary carbides and nitrides which exhibit remarkable properties half way between metals end ceramics. In this work, we have measured the complex dielectric constant Ɛ(ω) as a function of the composition of the sample. The samples are thin films of single crystal grown by magnetron sputtering and bulk polycristals processed by hot isostatic pressure. The measurements have been performed by electron energy loss spectroscopy (EELS) in the infrated - soft x-ray range and by V-UV ellipsometry in the infrated-ultraviolet range (1. 6 to 5. 5 eV). The dielctric properties of the Ti2A1C and Ti2A1N samples are remarkably different with the crystallographic orientation. In particular, a shift of the energy position of the plasmon of Ti1A1C with respect to the orientation of the crystal is observed. The dielectric constants of thin films of Ti2GeC, Ti2SnC and V2GeC have also been determined. A empirical semi-classical Drude-Lorentz model is fitted to the experimental spectra enabled us to extract the microscopic parameters such as the relaxation times and the electron density and the lifetime of free electrons. In addition, we show that the DC conductivity is indeed anisotropic in these compounds, a fact which has not been possible to address so far on macroscopic measurements. The dielectric function has been modelled in the framework of the time dependant density functional theory. Our calculations showed that the various dielctric functions in Ti2A1C are clearly influenced by strong local effect created by the presence of the d band in this material
Wätjen, Jörn Timo. "Microscopic Characterisation of Solar Cells : An Electron Microscopy Study of Cu(In,Ga)Se2 and Cu2ZnSn(S,Se)4 Solar Cells." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-199432.
Повний текст джерелаMitcov, Dmitri. "Rational functionalization of molecular magnetic materials : towards liquid crystalline phases, improved solubility and modulation of physical properties." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0029/document.
Повний текст джерелаThe work presented in this thesis was focused on the design and investigation of novel hybrid materials via ligand functionalization of the single-molecule magnets (SMMs) and electron transfer complexes. Chapter I contains general information about these two classes of the magnetic systems. In order to illustrate the motivation behind our work, a brief review on previously reported soft hybrid magnetic systems, is presented. Chapter II is dedicated to the functionalization of [Mn12]-based SMMs towards hybrid liquid crystalline systems via two different approaches: (a) the functionalization of peripheral ligands with strongly lipophilic groups (long alkyl chains), or (b) the grafting of mesogenic promoters through flexible aliphatic spacers. Chapters III – V are focused on cyanido-bridged molecular {Fe2Co2} squares that exhibit thermally or photo-induced electron transfer. Thus, in Chapter III, the possibility to modulate the electron transfer properties in {Fe2Co2} molecular squares via the use of different counter-anion is discussed. The functionalization with long aliphatic chains and its influence over the properties of {Fe2Co2} molecular squares in solid state and solutions are discussed in Chapter IV. Finally, the effect of the ligand functionalization with strongly electron density donating groups (methoxy) over the electron transfer properties of {Fe2Co2} molecular squares is investigated in Chapter V
Saidi, Wajdi. "Étude des phases dans des films minces d'oxyde de structure pérovskite en microscopie électronique en transmission." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2317.
Повний текст джерелаThe aim of this work is to characterize by transmission electron microscopy (TEM) at the scale of nm the crystal structure of thin films of BiFeO3 (BFO) grown on (001) LaAlO3 (LAO) and (001) Ca0,96Ce0,04MnO3//YAlO3 (CCMO//YAO). Indeed, BFO in the bulk state crystallizes in the R3c rhombohedral structure at room temperature with a ferroelectric polarization of ≈ 90 μC/cm2 in the [111]pc direction. In thin film, previous studies have shown that BFO can adopt a pseudo-tetragonal structure (T-like) with a c/a ratio ≈1.27 and a pseudo-rhombohedral structure (R-like) with a c/a ratio ≈ 1.07. This phase change improves the ferroelectric polarization and change the antiferromagnetic order. We studied BFO thin films of different thicknesses deposited on (001) LAO. For the film of 7 nm, no grain boundary was observed. The diffraction pattern shows only the fundamental reflections of the pseudo-cubic lattice. In thicker films, two types of grains are present T-like with a c/a ratio ≈ 1.24 and R-like with a c/a ratio ≈ 1.05. The R-like phase is generally present in the form of slanted R-like grains surrounded by a T-like matrix. The T-like and R-like phases were identified as a monoclinic Cm structure and rhombohedral R3c structure slightly distorted, respectively. For thin films of BFO (94 nm) deposited on CCMO//YAO (001), T-like and R-like phases are also present. The R-like phase is identified here as the rhombohedral R3c structure slightly distorted with a c/a ratio ≈ 1.09. The T-like phase is identified here as the tetragonal P4mm phase slightly distorted with a c/a ratio ≈ 1.27. Our results suggest that the increase of the compressive stress promotes the stabilization of the tetragonal phase P4mm
Zschiesche, Hannes. "Formation and segregation in cobalt silicide and manganese germanide thin films : correlative study by electron microscopy and atom probe tomography." Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0219.
Повний текст джерелаGermanide and silicide thin films have application in different field such as thermoelectricity, magnetism and/or microelectronics. This PhD thesis study the formation, structure and chemistry of Mn5Ge3 thin films, which is interesting due to its ferromagnetic property for possible spintronic devices, and of CoSi2 thin films, which are used as contact materials. Two new epitaxial relationships between Mn5Ge3 grains and (111)Ge have been identified. The chemical purity of Mn5Ge3 has been related to the deposition by magnetron sputtering: Mn5Ge3 thin films grown by reactive-diffusion are relatively pure while the significant incorporation of impurities in Mn5Ge3 grown by non-diffusive reaction is beneficial for the ferromagnetic property. Ti segregation to CoSi2 grain boundaries has been quantified in CoSi2 grown from a Co/Ti/Si thin film. Additionally, an inhomogeneous distribution of Ti at CoSi2 grain boundary has been related to the defect density. A method has been developed for correlative structural and chemical investigations at the atomic scale on selected interfaces. Finally, a method to quantify the triple junction segregation has been proposed
Boulineau, Adrien. "Contribution à la compréhension de la structure de Li2MnO3, de ses défauts et de phases dérivées." Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13747/document.
Повний текст джерелаIn order to get a better understanding of the complex structural evolutions occurring in the layered oxides like Li1+x(Ni0.425Mn0.425Co0.15)O2 materials when they are used as positive electrodes in lithium batteries, the structure of Li2MnO3 has been studied in detail. Obtained from several synthesis ways, annealed at various temperatures, this compound that can be considered as a model one regarding these complex materials has been the object of a crystallographic study where the use of electron microscopy was privileged. Two kinds of defects could be identified. From one part, the existence of stacking faults in the Li2MnO3 material has been proved and they have been visualized for the first time. Their consequences on X ray and electron diffraction patterns are explained allowing the unification of discrepancies existing in the bibliography. For other part, the study of the thermal stability of Li2MnO3 evidenced the appearance of spinel type defects when the annealing treatment is performed above 900°C. Finally the delithiation by acid leaching is studied and the lithium extraction mechanism is clarified. It is shown that this mechanism is the same whatever the particle size is
Amri, Noureddine. "Etude métallurgique des systèmes Fe-Nd, Fe-Dy et Fe-Nd-Dy : existence et stabilité de phases." Rouen, 1993. http://www.theses.fr/1993ROUES041.
Повний текст джерелаKovarik, Libor. "Microstructural study and modeling of metastable phases and their effect on strenghthening [sic] in Al-Mg-Cu-Si alloying system." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1149006665.
Повний текст джерелаNilforoushan, Niloufar. "Out-of-equilibrium electron dynamics of Dirac semimetals and strongly correlated materials." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS573/document.
Повний текст джерелаQuantum materials is a new term in condensed matter physics that unifies all materials in which strong electronic correlation governs physical properties of the system (e.g. Mott insulators) and materials whose electronic properties are determined by the geometry of the electronic wave function (e.g. Dirac materials). These materials show emergent properties– that is, properties that only appear by intricate interactions among many degrees of freedom, such as charge, spin and orbital, giving rise to topological properties of electrons. The study of these interactions and competitions between the relevant degrees of freedom demands applying ultrafast pump-probe techniques. Particularly, femtosecond laser pulses act only on the electrons and set them to an out-of-equilibrium state inexplicable by the Fermi-Dirac distribution. The ensuing dynamics involves various processes and the rate at which the relaxation occurs is related to the coupling constants. Moreover, in time-resolved pump-probe techniques light can act as an additional external parameter to change of the phase diagram – different from thermodynamic parameters. It gives us the opportunity of stabilizing new states inaccessible by quasi-adiabatic thermal pathways or eventually manipulating the physical properties of the systems.In this thesis, we performed different experiments in order to study the equilibrium and out-of-equilibrium properties of two correlated compounds: BaCo₁₋ₓNiₓS₂ and (V₁₋ₓMₓ)₂O₃.The first part of the project was mainly devoted to the study of BaNiS₂ that is the metallic precursor of the Mott transition in BaCo₁₋ₓNiₓS₂. By applying ARPES, we studied the electronic band structure of BaNiS₂ in its entire Brillouin zone. These results combined with some theoretical calculations give evidence of a novel correlation-induced and two-dimensional Dirac cone with d-orbital character. The band crossing is protected by the specific symmetries of the crystal structure. We also investigated the electronic band structure of the Mott insulator BaCoS₂ in its magnetic and nonmagnetic phases.In the second part, we studied the out-of-equilibrium electron dynamics of BaNiS₂ and (V₁₋ₓMx)₂O₃. By means of tr-ARPES and tr-reflectivity measurements, we observed an ultrafast and non-thermal renormalization of the Dirac cone in BaNiS₂ . This phenomenon is purely provoked by the electronic excitation and is stabilized by the interplay between the electrons and phonons. Moreover, by applying various pump-probe techniques (XFEL-based tr-XRD and tr-Reflectivity) we also explored the out-of-equilibrium phases of the prototype Mott-Hubbard material (V₁₋ₓMx)₂O₃ in different parts of its phase diagram. Our results show a transient non-thermal phase developing immediately after ultrafast photoexcitation and lasting few picoseconds in both metallic and insulating phases. This transient phase is followed by a structural distortion that corresponds to a lattice hardening and is marked by a “blue shift” of the A₁g phonon mode. These results underline the importance of the orbital filling as well as the strong effect of the selective electron-lattice coupling in the strongly correlated materials
Seelam, Uma Maheswara. "STRUCTURAL CHARACTERIZATION OF SPUTTER-DEPOSITED SS304+XAL (X = 0, 4, 7 AND 10 WT.%) COATINGS AND MECHANICALLY MILLED TI, ZR AND." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3527.
Повний текст джерелаPh.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr PhD
Abiyaala, Mohamed. "Etude en microscopie électronique par cryofracture des phases lyotropes du système SDS-Formamide." Rouen, 1993. http://www.theses.fr/1993ROUES048.
Повний текст джерелаDong, Chuang. "Structure et formation des quasicristaux et des phases cristallines approximantes dans les alliages Ti-Fe, Al-Cu-Fe(-Cr), Al-Cu-Co(-Si) et Al-Pd-Mn." Vandoeuvre-les-Nancy, INPL, 1991. http://docnum.univ-lorraine.fr/public/INPL_T_1991_DONG_C.pdf.
Повний текст джерелаBáborský, Tomáš. "Charakterizace automobilových vysokopevnostních ocelí pomocí elektronového mikroskopu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400477.
Повний текст джерелаGrumbling, Emily Rose. "Electronic Structure, Intermolecular Interactions and Electron Emission Dynamics via Anion Photoelectron Imaging." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195933.
Повний текст джерелаKrál, Michael. "Struktura a vlastnosti svarového spoje TiAl6V4/6061 zhotoveného technologií elektronového paprsku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318832.
Повний текст джерелаAi, Yong-le. "Novel direct field and torque control of six-phase induction machine with special phase current waveform." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/489.
Повний текст джерелаBabich, Danylo. "Electron-lattice coupling at the Mott transition driven by electric and/or by light pulse." Thesis, Nantes, 2020. http://www.theses.fr/2020NANT4049.
Повний текст джерелаMott insulators are a broad class of strongly correlated materials with numerous fascinating properties. These compounds undergo various types of Insulator to metal transitions (IMT). The recent discovery of a voltage-driven IMT, called Electric Mott Transition (EMT), has attracted much attention. This EMT can be volatile or non-volatile. Both properties lead to breakthrough applications, such as Mott artificial neurons or Mott memories. Therefore, a current frontier of research is to study and understand Insulator to metal transitions in Mott insulators driven out-of-equilibrium by external stimuli such as a short electric field or ultrafast laser pulses. In this context, the Ph.D. work focuses on the mechanism of the IMT driven by electric field and/or light pulses in Mott insulators. This work unravels the pivotal roles of hot carriers and electron-lattice coupling at the IMT driven by electric or light pulses. Our study of the iconic Mott system V2O3:Cr reveals the nature of the phase created under electric field. We show that hot carriers generated at the EMT induces a lattice compression in a filamentary path. The persistence of a metastable compressed phase is responsible for the EMT's non-volatility. On the other hand, our ultrafast IR pump-probe experiment suggests that the photoexcitation of V2O3:Cr launches a compressive strain wave promoting an Insulator to metal phase transformation. Finally, the concomitant application of light and electric pulses in the Mott insulator GaTa4Se8 confirms that the EMT is based on the accumulation of hot carriers, and enables the implementation of an artificial electrooptic Mott neuron
Delamare, José. "Etude microstructurale d'alliages Nd-Fe et Nd-Fe-Al : corrélation aux phases secondaires des aimants Nd-Fe-B." Rouen, 1992. http://www.theses.fr/1992ROUES058.
Повний текст джерелаGovindsamy, Matthew. "Sensorless speed estimation in three phase induction motors." Thesis, Port Elizabeth Technikon, 2002. http://hdl.handle.net/10948/139.
Повний текст джерелаPapathomas, Paul Michael. "Developments in gas-phase electron diffraction." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/12760.
Повний текст джерелаFender, Robert Scott. "Advances in gas-phase electron diffraction." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/14833.
Повний текст джерелаCortés, Huerto Robinson. "Phase transitions in many-electron systems." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527673.
Повний текст джерелаHavlík, Petr. "Svařování heterogenních svarových spojů Ti/Al slitin pomocí elektronového svazku." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-412926.
Повний текст джерелаWright, Timothy Grahame. "Studies of some gas-phase oxidation reactions using electron spectroscopy and the electronic structure of some small molecules." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358873.
Повний текст джерелаLu, Yuan-Ming. "Exotic phases of correlated electrons in two dimensions." Thesis, Boston College, 2011. http://hdl.handle.net/2345/2363.
Повний текст джерелаExotic phases and associated phase transitions in low dimensions have been a fascinating frontier and a driving force in modern condensed matter physics since the 80s. Due to strong correlation effect, they are beyond the description of mean-field theory based on a single-particle picture and Landau's symmetry-breaking theory of phase transitions. These new phases of matter require new physical quantities to characterize them and new languages to describe them. This thesis is devoted to the study on exotic phases of correlated electrons in two spatial dimensions. We present the following efforts in understanding two-dimensional exotic phases: (1) Using Zn vertex algebra, we give a complete classification and characterization of different one-component fractional quantum Hall (FQH) states, including their ground state properties and quasiparticles. (2) In terms of a non-unitary transformation, we obtain the exact form of statistical interactions between composite fermions in the lowest Landau level (LLL) with v=1/(2m), m=1,2... By studying the pairing instability of composite fermions we theoretically explains recently observed FQHE in LLL with v=1/2,1/4. (3) We classify different Z2 spin liquids (SLs) on kagome lattice in Schwinger-fermion representation using projective symmetry group (PSG). We propose one most promising candidate for the numerically discovered SL state in nearest-neighbor Heisenberg model on kagome lattice}. (4) By analyzing different Z2 spin liquids on honeycomb lattice within PSG classification, we find out the nature of the gapped SL phase in honeycomb lattice Hubbard model, labeled sublattice pairing state (SPS) in Schwinger-fermion representation. We also identify the neighboring magnetic phase of SPS as a chiral-antiferromagnetic (CAF) phase and analyze the continuous phase transition between SPS and CAF phase. For the first time we identify a SL called 0-flux state in Schwinger-boson representation with one (SPS) in Schwinger-fermion representation by a duality transformation. (5) We show that when certain non-collinear magnetic order coexists in a singlet nodal superconductor, there will be Majorana bound states in vortex cores/on the edges of the superconductor. This proposal opens a window for discovering Majorana fermions in strongly correlated electrons. (6) Motivated by recent numerical discovery of fractionalized phases in topological flat bands, we construct wavefunctions for spin-polarized fractional Chern insulators (FCI) and time reversal symmetric fractional topological insulators (FTI) by parton approach. We show that lattice symmetries give rise to different FCI/FTI states even with the same filling fraction. For the first time we construct FTI wavefunctions in the absence of spin conservation which preserve all lattice symmetries. The constructed wavefunctions also set up the framework for future variational Monte Carlo simulations
Thesis (PhD) — Boston College, 2011
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
Flament, Camille. "Etude des évolutions microstructurales sous irradiation de l'alliage d'aluminium 6061-T6." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI074/document.
Повний текст джерелаThe 6061-T6 Aluminium alloy, whose microstructure contains Al(Fe,Mn,Cr)Si dispersoids and hardening needle-shaped beta” precipitates (Mg, Si), has been chosen as the structural material for the core vessel of the Material Testing Jules Horowitz Nuclear Reactor. Because it will be submitted to high neutron fluxes at a temperature around 50°C, it is necessary to study microstructural evolutions induced by irradiation and especially the stability of the second phase particles. In this work, analytical studies by in-situ and ex-situ electron and ion irradiations have been performed, as well as a study under neutron irradiation. The precipitates characterization by Transmission Electron Microscopy demonstrates that Al(Fe,Mn,Cr)Si dispersoids are driven under irradiation towards their equilibrium configuration, consisting of a core/shell structure, enhanced by irradiation, with a (Fe, Mn) enriched core surrounded by a Cr-enriched shell. In contrast, the (Mg,Si) beta” precipitates are destabilized by irradiation. They dissolve under ion irradiation in favor of a new precipitation of (Mg,Si,Cu,Cr,Al) rich clusters resulting in an increase of the alloy’s hardness. beta’’ precipitates tend towards a transformation to cubic precipitates under neutron irradiation
Trambly, de Laissardière Guy. "Etude théorique de la structure électronique des matériaux quasicristallins." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10075.
Повний текст джерелаNoble-Eddy, Robert. "Gas-phase electron diffraction studies of unstable molecules." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4101.
Повний текст джерела