Дисертації з теми "Phonon energy"
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Hanna, Ann Catrina. "Energy resolved phonon scattering in glasses." Thesis, University of Glasgow, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280020.
Ong, Pang-Leen. "PHONON-ENERGY-COUPLING-ENHANCEMENT EFFECT AND ITS APPLICATIONS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/652.
Damart, Tanguy. "Energy dissipation in oxide glasses." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1189/document.
The origin of sound attenuation at low and high frequency in glasses stays elusive mainly because of the complex temperature and frequency dependence of the phenomena at its root. Indeed, the presence of complex structures and multi-scale organizations in glasses induce the existence of relaxation time ranging from the second to the femto-second and of spatial correlation ranging from the Angström to a hundred nanometers. At low-frequency, a better understanding of the phenomena at the origin of dissipation would be beneficial to several applications. For example, the multi-layers coating the mirrors of gravitational waves detectors consists of a superposition of two oxide glasses: silicate (SiO2) and tantalum pentoxide (Ta2O5), are an important source of dissipation. At high frequency, the study of dissipation raises theoretical questions about the link between attenuation and dissipation as well as between loclt asymmetry and dissipation. In the present study, we conducted an analysis of the interaction between mechanical waves and the structure of two oxide glasses using simulation techniques such as non-equilibrium molecular dynamics. At high-frequencies, we implemented and used mechanical spectroscopy to measure dissipation numerically and performed in parallel an analytical development based on the projection of the atomic motion on the vibrational eigenmodes. At low-frequencies, we used molecular dynamics to gather sets of thermally activated events that we classed in three categories based on topologically distinct atomic motions and from which we predicted dissipation numerically using a refreshed TLS model
Kulikowski, Anoushka. "Phonon studies of energy loss in vertical tunnelling structures." Thesis, Lancaster University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286990.
Giltrow, M. "Phonon study of vertical resonant structures." Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337346.
Sklan, Sophia Robin. "Dynamical tuning of phonon transport for information and energy control." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103231.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 145-164).
Controlled transport of energy and information is of paramount importance. It remains challenging, however, partially from the difficulty in controlling their physical carriers. Steering electrons and photons is now routine, yet atomic vibrations (quantized as phonons) are hard to control. This is partly due to the centrality of phonons in the disordered transport of energy as heat, but even in ordered sound waves problems persist. Phonons can readily couple to each other or to other degrees of freedom, degrading their energy or information content. Reversing these couplings, thereby regulating atomic motion, only recently became plausible. This increased control would reduce parasitic losses and turn phonons into information carriers. Dynamical effects are a crucial and under-examined aspect of this control as static devices are insufficient for changing external conditions. Dynamical control adds flexibility and versatility to phononic systems. Essentially, dynamical control requires tunable materials, materials whose physical properties depend on an external signal. Dynamical tuning is sensitive to the relative frequencies of the tuning signal and the controlled phonons. We develop an intuitive framework of the temporal modulation regimes. In low frequency tuning, phonons can adapt adiabatically to the material's changes. A variety of signals can be temporally and spatially modulated to tune phonon transport in this regime. We apply this adiabatic perspective to analyze dynamical effects in thermal cloaks. Tuning signals near the frequency of some phonon mode can produce resonant couplings. This hybridization can produce large changes in phonon properties. We apply this hybridization to develop a rigorously nonreciprocal phononic computer using magneto-acoustic materials that can outperform conventional computers in some tasks. At high frequencies, phonons can only respond perturbatively to the tuning signal's changes. This regime is generally limited to optical control but it opens up new avenues for control. Employing an alternative approach to optical coupling, we develop a model of inverse acousto-optics (tuning the speed of sound with optical intensity) and dynamical phonon localization.
by Sophia Robin Sklan.
Ph. D.
Chen, Dye-Zone A. (Dye-Zone Abraham) 1973. "Energy transmission through and along thin films mediated by surface phonon-polaritons." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42067.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 131-138).
Surface phonon-polaritons are hybrid electromagnetic modes that are the result of photons coupling to transverse optical phonons. Recently, these surface modes have received much renewed interest primarily due to the fact that micro-fabrication techniques can now routinely create structures at the length scales of interest (nanometers to microns). This thesis investigates the transmission of energy mediated by surface phonon-polaritons. First, the heat flux transported along the in-plane direction of a thin film is explored. A kinetic theory-based calculation is performed using a diffusion approximation. These results are further confirmed by simulations using fluctuational electrodynamics. It was found that for amorphous silicon dioxide films tens of nanometers thick, the in-plane heat flux carried by surface phonon-polaritons can exceed the heat flux carried by phonons in the film. The results also show that the effective thermal conductivity due to surface polaritons increases with decreasing film thickness, offering a method to potentially offset the reduction in thermal conductivity due to increased interface scattering of phonons in crystalline thin films. Both calculations point to the propagation length of the surface phonon-polariton as the source for the large heat flux. An experimental measurement of the surface phononpolariton propagation length on amorphous silicon dioxide is performed using attenuated total reflection and is found to agree well with the calculated value. The last part of this thesis examines the energy transmission in the direction normal to the plane of the film. Specifically, the transmission of light through an amorphous silicon dioxide film perforated by sub-wavelength holes is experimentally measured. A five-fold increase through the perforated film versus through a solid film is observed in discrete frequency ranges, which strongly suggests the involvement of surface phonon-polaritons.
by Dye-Zone A. Chen.
Ph.D.
Minnich, Austin Jerome. "Exploring electron and phonon transport at the nanoscale for thermoelectric energy conversion." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67593.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 147-155).
Thermoelectric materials are capable of solid-state direct heat to electricity energy conversion and are ideal for waste heat recovery applications due to their simplicity, reliability, and lack of environmentally harmful working fluids. Recently, nanostructured thermoelectrics have demonstrated remarkably enhanced energy conversion efficiencies, primarily due to a reduction in lattice thermal conductivity. Despite these advances, much remains unknown about heat transport in these materials, and further efficiency improvements will require a detailed understanding of how the heat carriers, electrons and phonons, are affected by nanostructures. To elucidate these processes, in this thesis we investigate nanoscale transport using both modeling and experiment. The first portion of the thesis studies how electrons and phonons are affected by grain boundaries in nanocomposite thermoelectric materials, where the grain sizes are smaller than mean free paths (MFPs). We use the Boltzmann transport equation (BTE) and a new grain boundary scattering model to understand how thermoelectric properties are affected in nanocomposites, as well as to identify strategies which could lead to more efficient materials. The second portion of the thesis focuses on determining how to more directly measure heat carrier properties like frequency-dependent MFPs. Knowledge of phonon MFPs is crucial to understanding and engineering nanoscale transport, yet MFPs are largely unknown even for bulk materials and few experimental techniques exist to measure them. We show that performing macroscopic measurements cannot reveal the MFPs; instead, we must study transport at the scales of the MFPs, in the quasi- ballistic transport regime. To investigate transport at these small length scales, we first numerically solve the frequency-dependent phonon BTE, which is valid even in the absence of local thermal equilibrium, unlike heat diffusion theory. Next, we introduce a novel thermal conductivity spectroscopy technique which can measure MFP distributions over a wide range of length scales and materials using observations of quasi-ballistic heat transfer in a pump-probe experiment. By observing the changes in thermal resistance as a heated area size is systematically varied, the thermal conductivity contributions from different MFP phonons can be determined. We present the first experimental measurements of the MFP distribution in silicon at cryogenic temperatures. Finally, we develop a modification of this technique which permits us to study transport at scales much smaller than the diffraction limit of approximately one micron. It is important to access these length scales as many technologically relevant materials like thermoelectrics have MFPs in the deep submicron regime. To beat the diffraction limit, we use electron-beam lithography to pattern metallic nano dot arrays with diameters in the hundreds of nanometers range. Because the effective length scale for heat transfer is the dot diameter rather than the optical beam diameter, we are able to study nanoscale heat transfer while still achieving ultrafast time resolution. We demonstrate the modified technique by measuring the MFP distribution in sapphire. Considering the crucial importance of the knowledge of MFPs to understanding and engineering nanoscale transport, we expect these newly developed techniques to be useful for a variety of energy applications, particularly for thermoelectrics, as well as for gaining a fundamental understanding of nanoscale heat transport.
by Austin Jerome Minnich.
Ph.D.
Mafra, Daniela Lopes. "Using inelastic scattering of light to understand the nature of electron-phonon interactions and phonon self-energy renormalizations in graphene materials." Universidade Federal de Minas Gerais, 2012. http://hdl.handle.net/1843/MPDZ-8Y4GEG.
Na última década, muitos avanços teóricos e experimentais foram alcançados na física do grafeno. Em particular, a Espectroscopia Raman tem sido muito importante para elucidar propriedades físicas e químicas em sistemas de grafeno. Nessa tese nós usamos a Espectroscopia Raman para estudar alguns dos efeitos do acoplamento elétron-fônon no grafeno de camada única e de dupla camada e para obter informações sobre a estrutura eletrônica e vibracional do grafeno de camada dupla. As renormalizações das energias dos fônons tem sido estudadas basicamente para fônons com vetor de onda nulo (q=0). Aqui, nós combinamos a Espectroscopia Raman com aplicação de tensão de porta, para estudar, em grafeno de camada única, as bandas originadas do processo Raman com dupla ressonância (DDR) com etores de onda q0. Nós observamos os efeitos de decaimento dos fônons com o aumento da tensão de porta e esse efeito é o oposto do que é observado para os fônons com q=0. Nós mostramos que esse tipo de renormalização é uma assinatura dos fônons com vetor de onda q2K que vem de um processo de camada única, os modos de fônons que contribuem para a banda Raman G*, em ~2450cm-1 e para outros cinco picos provenientes de combinação de modos na região de frequência 1700-2300cm-1. Combinando a teoria do processo DRR com o efeito de renormalização de fônons, nós mostramos uma nova técnica para usar a Espectroscopia Raman para identificar cada modo Raman apropriadamente. Nó também estudamos o comportamento dos modos ópticos do grafeno de camada dupla combinando o espalhamento Raman e a aplicação de tensão de porta em dispositivos desse material. Nós observamos que a banda G se divide em duas quando o nível de Fermi da amostra é mudado e isso é explicado em termos da mistura dos modos de fônon Raman (Eg) e infravermelho (Eu) devido a diferença de concentração de carga nas duas camadas. Nós mostramos que a comparação entre os dados experimentais e o modelo teórico não dá apenas informação sobre a concentração de carga total no dispositivo de grafeno de camada dupla, mas também nos permite quantificar separadamente a quantidade de cargas não intencionais provenientes da camada de cima e de baixo do sistema e, portanto caracterizar a interação do grafeno de camada dupla com o ambiente a sua volta. Na segunda parte dessa tese, a dispersão de elétrons e fônons perto do ponto K do grafeno de camada dupla é investigada atravé do estudo da banda G' usando várias energias de excitação de laser na região do infravermelho e do visível. A estrutura eletrônica foi analisada dentro da aproximação de ligações-forte e os parâmetros Slonczewski-Weiss-McClure (SWM) foram obtidos através do comportamento dispersivo da banda G' considerando-se tanto o processo DRR interno, quanto o externo. Nós mostramos que os parâmetros SWM obtidos considerando-se que o processo DRR interno está em melhor acordo com os valores obtidos por outras técnicas experimentais, sugerindo fortemente que o processo interno é o principal responsável pela banda G' no grafeno. Além disso, a dependência da intensidade dos quatro picos que compõe a banda G' do grafeno de camada dupla com a energia de excitação de laser e com a potência do laser é explorada e explicada em termos do acoplamento elétron-fônon e do relaxamento dos elétrons foto-excitados. Nós mostramos que o relaxamento dos elétrons ocorre predominantemente pela emissão de fônons acústicos de baixa energia e as diferentes combinações dos processos de relaxamento determinam as intensidades relativas dos quatro picos que dão origem à banda G'. Esse efeito nos fornece informações importantes sobre a dinâmica dos elétrons e fônons e precisa ser levado em conta para aplicações do grafeno de camada dupla do campo nanotecnológico.
Sidorova, Mariia. "Timing Jitter and Electron-Phonon Interaction in Superconducting Nanowire Single-Photon Detectors (SNSPDs)." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22296.
This Ph.D. thesis is based on the experimental study of two mutually interconnected phenomena: intrinsic timing jitter in superconducting nanowire single-photon detectors (SNSPDs) and relaxation of the electron energy in superconducting films. Microscopically, a building element of any SNSPD device, a superconducting nanowire on top of a dielectric substrate, represents a complex object for both experimental and theoretical studies. The complexity arises because, in practice, the SNSPD utilizes strongly disordered and ultrathin superconducting films, which acoustically mismatch with the underlying substrate, and implies a non-equilibrium state. This thesis addresses the complexity of the most conventional superconducting material used in SNSPD technology, niobium nitride (NbN), by applying several distinct experimental techniques. As an emerging application of the SNSPD technology, we demonstrate a prototype of the dispersive Raman spectrometer with single-photon sensitivity.
Stanton, Nicola Marie. "Experimental studies of electron-phonon interactions in gallium nitride." Thesis, University of Nottingham, 2001. http://eprints.nottingham.ac.uk/14212/.
Al-Jawhari, Hala A. "Study of energy loss by a hot two-dimensional electron gas." Thesis, Lancaster University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287252.
Cross, Andrew John. "The electron-phonon interaction in GaAs/(AlGa)As quantum wells." Thesis, University of Nottingham, 2001. http://eprints.nottingham.ac.uk/14316/.
Hardikar, Rahul Padmakar. "Dynamic electron-phonon interactions in one-dimensional models." Diss., Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-11092007-143010.
Zhou, Jiawei. "Ab initio simulation and optimization of phonon drag effect for lower-temperature thermoelectric energy." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100088.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 81-85).
In recent years, extensive efforts have been devoted to searching for materials with high thermoelectric (TE) efficiency above room temperature for converting heat into electricity. These efforts have led to significant advances with a record-high zT above 2. However, the pursuit of higher TE performance at lower temperatures for cooling and refrigeration applications receives much less attention. Today's most widely-used thermoelectric materials below room temperature are still (Bi,Sb) 2(Te,Se)3 material system, discovered 60 years ago with a maximum zT around 1. This thesis develops the first-principles simulation tools to study the phonon drag effect - a coupling phenomenon between electrons and non-equilibrium phonons - that leads to a large Seebeck coefficient at low temperatures. Phonon drag effect is simulated successfully from first-principles for the first time and results compare well with experimental data on silicon. While the common wisdom always connects a significant phonon drag effect to a high thermal conductivity, a key insight revealed from the simulation is that phonons contributing to phonon drag and to thermal conductivity do not spectrally overlap. Even in a heavily-doped silicon sample with 1019 cm-3 doping concentration, phonon drag still contributes to -50% of the total Seebeck coefficient. By selectively scattering phonons contributing to heat conduction but not to phonon drag, a large improvement in thermoelectric figure of merit zT is possible. An ideal phonon filter is shown to tremendously enhance zT of n-type silicon at room temperature by a factor of 20 to ~0.25, and the enhancement reaches 70 times at lOOK. A practical phonon filtering method based on nanocluster scattering is shown to enhance zT due to reduced thermal conductivity and optimized phonon drag effect. This work opens up a new venue towards better themoelectrics by harnessing non-equilibrium phonons. More material systems can be systematically studied with the developed simulation tools.
by Jiawei Zhou.
S.M.
Pentland, Ian Alisdair. "A phonon emission study of quasi-1D electron gases." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325695.
Osborne, Daniel Josiah. "A Nanoengineering Approach to Oxide Thermoelectrics For Energy Harvesting Applications." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/36133.
Master of Science
Koster, Sophie Amelia. "Energy Levels and Dynamics of Tm²⁺ Doped into AMX₃ Salts." Thesis, University of Canterbury. Physics and Astronomy, 2014. http://hdl.handle.net/10092/9643.
Devitt, Andrew Maurice. "Time and angle resolved phonon absorption in the fractional quantum hall regime." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342525.
Kaul, Pankaj B. "Thermal Transport in Tin-Capped Vertically Aligned Carbon Nanotube Composites for Thermal Energy Management." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1383515941.
Pfau, Charlotte [Verfasser], S. [Akademischer Betreuer] Schweizer, R. [Akademischer Betreuer] Wehrspohn, and U. [Akademischer Betreuer] Rogulis. "Low phonon energy glass ceramics for efficient rare-earth luminescence / Charlotte Pfau. Betreuer: S. Schweizer ; R. Wehrspohn ; U. Rogulis." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2014. http://d-nb.info/1076503195/34.
Galparsoro, Larraza Oihana. "Phonon and electron excitations in diatom abstraction from metallic surfaces." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0417/document.
The rationalization of elementary processes at surfaces is of prime importance for numerous natural and technological areas. From a fundamental pointof view, the way the energy concomitant to any chemical reaction is distributed among the desorbing molecules degrees-of-freedom and the surface is far frombeing fully pictured. In this work, quasiclassical molecular dynamics (QCT)simulations have been carried out to investigate this issue for the recombination ofH2 and N2 resulting from atomic adsorbate abstraction by atom scattering off theW(100) and W(110) covered surfaces, these processes being of relevance inplasma-wall interactions. Potential energy surfaces, built from density functional(DFT) theory calculations, have been used to simulate, within the framework ofclassical dynamics (including semi-classical corrections), the subpicosecond Eley-Rideal and Hot-Atom processes. The implementation of effective models to accountfor energy dissipation to surface phonons and electron-hole pair excitations, have allowed to rationalize the non-adidabatic dynamics of atom abstraction at metalsurfaces
Vallerini, Barbosa Itália. "Nanocristaux oxydes luminescents pour le développement de nanosondes de température in vivo." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALI125.
Biological thermal modifications are common events during abnormal cellular metabolic activities. Indeed, thermal aberrations – such as an increase in local tissue temperature – are directly related to the detection of inflamed areas, the presence of tumors, or other diseases. In addition to contributing to the diagnosis of diseases, the determination of local temperature in biological systems can also help with their treatment. For instance, in hyperthermia, the increase in temperature must be induced in tumor tissues up to cytotoxic levels in order to kill cancer cells and therefore, it assists in the cancer treatment. However, the increase in temperature must be carried out in a controlled and well-localized manner to target cancer cells, while avoiding overheating of surrounding healthy tissue. Furthermore, to determine such biological aberrations, temperature variations must be accurately determined. The thermometric performance of the nanothermometers was determined by calculating the relative thermal sensitivity (S_r) using the ratiometric luminescence intensity approach. Furthermore, our study made it possible to raise some hypotheses that can effectively contribute to the thermometric performance of thermal probes. We use the technique of the intensity ratio of two luminescence peaks for which the values of S_r can be optimized by co-doping the nanocrystals with two, or more, Ln3+ ions and by using oxide matrices presenting different phonon energies. Thus, due to its generic nature and synthesis flexibility, the Pechini method was chosen to synthesize several oxide matrices, Y2O3, Y2Ge2O7, Y3Al5O12 (YAG), Y3BO6 and YBO3. The nanocrystals were firstly monodoped with Nd3+ and posteriorly, codoped with Nd3+ -Yb3+ to improve the thermal probe properties within the biological windows of near infrared. In addition, we optimized the doping concentrations in the host matrices for greater efficiency in luminescence detection in biological organisms. We experimentally observed that Sr values are strongly impacted to the phonon energy of the matrix. We analyzed that by Nd3+ -Yb3+ codoping the thermometric performance of nanocrystals is improved compared to nanocrystals mono doped with Nd3+. Our study of different oxides shows that the YAG and Y2O3 matrices are the most promising matrices for the luminescence nanothermometry in vivo application. Lastly, YAG individual nanocrystals (non-agglomerated as in the case of Pechini syntheses) of size 60 nm and controlled morphology were obtained in solution by the solvothermal method to advance in further studies in biological applications. We observed that the YAG nanothermometers suitable for the purpose have a S_r equal to 0.47 %·K-1 and a thermal resolution of 0.3 K. In vivo experimental tests are required to validate the findings of this study; however, our results obtained on the performance of YAG: Nd3+ -Yb3+ nanocrystals has been showing high potential for in vivo applications of ratiometric luminescence nanothermometry
Kennedy, Jermaine L. "Investigations of fiber optic temperature sensors based on Yb:Y3Al5O12." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001566.
Swift, Angela Marion. "The development of a cryogenic phonon detector, based on the coupling of superconducting tunnel junctions to indium antimonide crystals : with applications in X-, #gamma#- and #beta#-ray spectroscopy antimonide." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294274.
Timrov, Iurii. "Ab initio study of plasmons and electron-phonon coupling in bismuth: from free-carrier absorption towards a new method for electron energy-loss spectroscopy." Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/docs/00/82/37/58/PDF/thesis.pdf.
This work has been devoted to the theoretical study of bulk semimetallic bismuth with methods based on the density functional theory (DFT). Effects of spin-orbit coupling and of the exchange-and-correlation functionals in the local density (LDA) and generalized gradient approximation (GGA) have been systematically investigated. I have found that electron and hole pockets at the Fermi level are accurately reproduced, which has enabled me to successfully interpret the pump-probe experiments in the photoexcited bismuth performed in the Laboratoire des Solides Irradiés. The strong dependence on the electronic wave vector, of the calculated electronic coupling of the upper valence band with the zone-center A1g LO phonon, explains the observation of a strongly k-dependent oscillation amplitude of the upper valence band in time-resolved photoemission experiments upon activation of the coherent A1g phonon under photoexcitation. I have also shown that the presence of local extrema in the conduction and valence bands structure, where the carrier mass can be as large as 18 m0, favours an accumulation of photoexcited carriers in these extrema and contributes to the augmentation of the plasma frequency as a function of time after the photoexcitation, an effect which has no analogy in other materials (as yet). Finally, I have developed a new ab initio approach in the time-dependent density functional perturbation theory (TDDFPT), which allows us to calculate the electronic response of materials for any momentum transfer. This approach based on the Lanczos recursion method has enabled me to calculate for the first time the electron energy-loss spectrum of Bi in the 0-100 eV energy range, bridging the gap between valence and core losses. This method opens the way to the routine calculation of surface plasmons
Wong, Basil T. "THERMAL HEAT TRANSPORT AT THE NANO-SCALE LEVEL AND ITS APPLICATION TO NANO-MACHINING." UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/387.
Hardikar, Rahul Padmakar. "Investigation of order parameters and critical coupling for the Peierls Extended Hubbard Model at one-quarter filling." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-11112004-120413.
Hague, James P. "Band to Mott transition in the infinite dimensional Holstein model." Thesis, University of Warwick, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369426.
Li, Yuting. "Simulations and Electronic Structure of Disordered Silicon and Carbon Materials." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1395410498.
Mai, Thuc T. "Optical spectroscopy of cooperative phenomena and their symmetries in solids." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555629359625425.
Berthou, Simon. "Etude opto-électronique des mécanismes de relaxation des électrons de haute énergie dans les hétérostructures en graphène." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC133/document.
In this thesis we study the electron-phonon coupling in graphene and in particular theinfluence of the substrate in the aforementioned coupling. We want to quantify by optoelectronicalmeasurements the coupling between the phonon modes of the substrate. It might be the couplingwith Surface Phonon Polaritons (SPPs) in case of isotropic substrates as SiO2 or Hyperbolic PhononPolaritons (HPPs) in case of highly anisotropic substrates. We start by a review about the state of theart on electron phonon coupling in graphene. Then we introduce the different experimental methodsused during this thesis. We present experimental results on an graphene on SiO2 sample. We identifythe different coupling regimes and point out the necessity of working on ultra clean samples toinvestigate the high energy regimes. Finally we prensent experimental results on a graphene on BNsample where we identify a new coupling regime consisting in HPP emission in a Zener-Klein transportregime
Wang, Yichun. "LEAKAGE CURRENT REDUCTION OF MOS CAPACITOR INDUCED BY RAPID THERMAL PROCESSING." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/640.
Almutairi, Alanoud. "Electronic band structure equations and Fermi surface evolution from 2D materials to 3D layered superconducting compounds." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/134414/1/Alanoud%20Mulfi%20Z_Almutairi_Thesis.pdf.
Light, Brandon W. "Energy-efficient photon mapping." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-051007-092224/.
Keywords: mobile devices; photon mapping; global illumination; ray tracing; energy; mobile; computer graphics. Includes bibliographical references (leaves 66-68).
Jamison, John S. "Time and Space Resolved Spin-Heat Transport in the Magnetic Insulator Yttrium Iron Garnet." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586740671277489.
Hamyeh, Sobhi. "Étude de transfert d’énergie par des excitations de surface." Thesis, Troyes, 2020. http://www.theses.fr/2020TROY0013.
The size of electronic components has recently been reduced to a few tens of nanometers. This perpetual decrease in the size of modern electronic components and the increase in their operating speeds and frequencies inevitably leads to hot spots, which are hazards leading to system failure if left for long periods of time. The first objective of this thesis is to optimize efficient and practical techniques for heat dissipation from electronic nano-components. The second objective of this thesis is to provide ways to control the energy flow in order to meet these scientific and industrial needs.We study the transport by surface phonon-polariton (PhPS), which are electromagnetic surface waves resulting from the coupling between an electric field in the mid-infrared and optical phonons in a polar material. We also study the transport mechanisms by a two-dimensional electron gas (2DEG) confined in a quantum well formed at hetero-interfaces. We demonstrate that the excitation of PhPS modes in polar layers a few nanometers thick deposited on conventional semiconductors can improve the energy flow considerably, and consequently dissipate the heat accumulated in nano-components. We also demonstrate that the stain field in the AlN layer plays a critical role in governing the transport properties of the two-dimensional electron gas confined in the AlN/ GaN quantum well
Hendry, D. "Jet production in photon-photon interactions." Thesis, University of Glasgow, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375434.
Walker, Ian W. "Exclusive charged pion production in photon-photon interactions." Thesis, Lancaster University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305949.
Kang, Ji-Hwan. "Energy transfer enhancement of photon upconversion systems for solar energy harvesting." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45846.
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Cataloged from PDF version of thesis.
Includes bibliographical references (p. 121-122).
Nuclear oil well logging tools utilizing radioisotope sources of photons are used ubiquitously in oilfields throughout the world. Because of safety and security concerns, there is renewed interest in shifting to electronically-switchable accelerator sources. Investigation of accelerator sources opens up the opportunity to study higher-energy sources. In this thesis, sources with a 10 MeV endpoint are examined, a several-fold increase over traditional techniques. The properties of high-energy photon transport are investigated for potential new or improved well logging measurements. Two obvious processes available with a high-energy photon source are pair production and photo neutron emission. A new measurement of formation density is proposed based on the annihilation radiation produced after the pair production of high-energy source photons in the rock formation. With a detector spacing of 55 cm, this measurement exhibits a sensitivity to density with a dynamic range of 10 across a typical range of formation density (2.0 - 3.0 g/cc), the same as traditional measurements. Increases in depth of investigation for these measurements can substantially improve the sampling of the formation and thus the quality and relevance of the measurement. Being distributed in angle and space throughout the formation, a measurement based on anni-hilation photons exhibits a greater depth of investigation than traditional methods. For a detector spacing of 39 cm (equivalent to a typical spacing for one detector in traditional approaches), this measurement has a depth of investigation of 8.0 cm while the traditional measurement has a depth of investigation of 3.6 cm.
(cont.) For the 55 cm spacing, this depth is increased to 9.4 cm. Concerns remain for how to implement an accelerator source in which energy spectroscopy, essential for identifying an annihilation peak, is possible. Because pair production also depends on formation lithology, the effects of chemical composition on annihilation photon flux are small (<20 %) for the studied geometry. Additionally, lithology measurements based on attenuation at high energies show too small an effect to be likely to produce a useful measurement. Photoneutron production cross sections at this energy are too small to obtain a measurement based on this process.
by Eric D. Johnson.
Ph.D.