Дисертації з теми "Phonons – Transport"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Phonons – Transport".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
Davaasambuu, Jav, Friedrich Güthoff, Klaudia Hradil, and Götz Eckold. "Phonons in demixing systems." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-188279.
Davaasambuu, Jav, Friedrich Güthoff, Klaudia Hradil, and Götz Eckold. "Phonons in demixing systems." Diffusion fundamentals 12 (2010) 109, 2010. https://ul.qucosa.de/id/qucosa%3A13916.
Tavakoli-Ghinani, Adib. "Transport de phonons dans le régime quantique." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY090/document.
This PhD entitles Phonon heat transport in the quantum regime is based on the analysis of the thermal properties of confined systems at very low temperature.The context of this subject is putting the systems in two extreme conditions (low temperature and low dimensions) and understand the fundamental thermal properties coming from these limits.The studied samples during this PhD that are suspended structures (membrane or nanowire) are elaborated from amorphous silicon nitride.By lowering the temperature, the phonon characteristic lengths like the mean free path or the phonon dominant wavelength increase. When these characteristic lengths exceed lateral dimensions of the system, the boundary scattering will govern the thermal properties. In the boundary scattering, phonon transport goes from boundary limited scattering (Casimir regime) to ballistics regime (quantum limit). In this ballistic regime, the heat current can be expressed using the Landauer model. The thermal conductance is then expressed as: K=N_α q T where N_α is the number of populated vibrational modes, q=((π²k_B^2)T)⁄3h is the universal value of quantum of thermal conductance, and T is the transmission coefficient.In this work, thermal conductance measurements of suspended nanowires have been performed down to very low temperature. A measurement platform having an unprecedented sensitivity have been developed that can measure a variation of energy smaller than the attojoule. These new sensors allow the measurement of thermal properties of 1D phonon waveguide in the quantum regime of heat transport. We show that the transmission coefficient is the dominant factor that set the thermal conductance value. It depends on the dimension and the shape of the reservoirs, and the nature of the material in use rendering difficult the measurement of the quantum of thermal conductance. We show that in all of the SiN structures, the thermal transport could be dominated by low energy excitations that exist in amorphous solids (a-solids).The second important set of experiments concerns the specific heat. We have studied suspended the thermal properties of very thin SiN membranes that are thought to be 2D phonon cavities. We show that the temperature dependence of the specific heat departs from the quadratic behavior as expected at very low temperature. The true models giving a quantitative explanation of the results is still under consideration. The presence of tunneling two-level systems in amorphous materials could be one possible explanation for the high absolute value of specific heat that has been measured
Heron, Jean-Savin. "Transport des phonons à l'échelle du nanomètre." Phd thesis, Grenoble 1, 2009. http://www.theses.fr/2009GRE10183.
To understand the mechanisms of the heat transport at small length scales, we are fabricating complex nano-devices and measuring the thermal conductance of suspended silicon nanowires at cryogenic temperatures, principally by the 3 omega method. We demonstrate the dependance of the phonon transport to the dimensions and the geometry of these nanostructures. For nanowires with a length between 8 and 10 µm, and a section of 200x100 nm^2, we observe a deviation of the diffusive regime of Casimir below 5K, which can be explained by taking account the roughness of the surface of the nanowires. When the temperature decreases, the wave length of the phonons increases and ballistic collisions at the surface occur, implying an increase of the mean free path of the phonons, considered before as constant. Important mesoscopic effects on the phonons transport induced by the geometry of the nanowires have been measured for the first time. The presence of zigzag on the length of the wires blocks the current of phonons on a wide range of temperature, with as consequence an important decrease in the order of 40 % of the thermal conductance in comparison with straight nanowires. Experiments in parrallel on silcon NEMS have been performed at low temperatures, and compared with MEMS of same geometries. The mechanical behavior of silcon nanostructures at low scale is also aborded. At the end, first prototypes of zeptoJoules nanocalorimeters (10^-21 J) are presented, which allow thermal characterization of single mesoscopic object
Heron, Jean-Savin. "Transport des phonons à l'échelle du nanomètre." Phd thesis, Grenoble 1, 2009. http://tel.archives-ouvertes.fr/tel-00461703.
Hamzeh, Hani. "Résolution de l’équation de transport de Boltzmann pour les phonons et applications." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112371/document.
This work is dedicated to the study of phonon transport and dynamics via the solution of Boltzmann Transport Equation (BTE) for phonons. The Monte Carlo stochastic method is used to solve the phonon BTE. A solution scheme taking into account all the different individual types of Normal and Umklapp processes which respect energy and momentum conservation rules is presented. The use of the common relaxation time approximation is thus avoided. A generalized Ridley theoretical scheme is used instead to calculate three-phonon scattering rates, with the Grüneisen constant as the only adjustable parameter. A method for deriving adequate adjustable anharmonic coupling coefficients is presented. Polarization branches with real nonlinear dispersion relations for transverse or longitudinal optical and acoustic phonons are considered. Zone-center longitudinal optical (LO) phonon lifetimes are extracted from the MC simulations for GaAs, InP, InAs, and GaSb. Decay channels contributions to zone-center LO phonon lifetimes are investigated using the calculated scattering rates. Vallée-Bogani’s channel is found to have a negligible contribution in all studied materials, notably GaAs. A comparison of phonons behavior between the different materials indicates that the previously reported LO phonon lifetimes in InAs and GaSb were quite underestimated in the literature. For the first time, to our knowledge, a coupling of two independent Monte Carlo solvers, one for charge carriers [PhD manuscript, E. TEA], and one for phonons, is undertaken. Hot phonon effect on charge carrier dynamics is studied. It is shown that the relaxation time approximation overestimates the phonon bottleneck effect. The phonon MC solver is extended to solve the phonon’s BTE in real space simultaneously with the reciprocal space, to study phonon and heat transport. Ridley’s generalized theoretical scheme is utilized again with simulation particles interacting directly together. Energy and momentum conservation laws are rigorously implemented. Umklapp processes effect on the total phonon momentum is thoroughly reproduced, as for the anharmonic interactions effect on resulting phonon directions. This is thanks to a procedure taking in consideration the respective vector directions during an interaction, instead of the randomization procedure usually used in literature. Our preliminary results show the limit of the analytic macroscopic heat conduction equation
Iskandar, Abdo. "Phonon Heat Transport and Photon-phonon Interaction in Nanostructures." Thesis, Troyes, 2018. http://www.theses.fr/2018TROY0010.
In this dissertation, we investigate phonon heat transport and phonon interaction with optical elementary excitations in nanostructures. In the first chapter, we present an introduction to the physics of phonons and optical elementary excitations in nanostructured materials. The second chapter provides a detailed description of the samples growth and fabrication procedures and the various characterization techniques used. In the third chapter, we demonstrate that phonons and photons of different momenta can be confined and interact with each other within the same nanostructure. In the fourth chapter, we present experimental evidence on the change of the phonon spectrum and vibrational properties of a bulk material through phonon hybridization mechanisms. We demonstrate that the phonon spectrum of a bulk material can be altered by hybridization between confined phonon modes in nanostructures introduced on the surface of the material and the underlying bulk phonon modes. Shape and size of the nanostructures made on the surface of the substrate have strong effects on the phonon spectrum of the bulk material itself. In the fifth chapter, we demonstrate that at low temperatures (below 4 K) the nanowire specific heat exhibits a clear contribution from an essentially two-dimensional crystal. We also demonstrate that transitions from specular to diffusive elastic transmission and then from diffusive elastic to diffusive inelastic transmission occur at the interface between nanowires and a bulk substrate as temperature increases. Perspectives include the control of bulk material thermal properties via surface nanostructuring
France-Lanord, Arthur. "Transport électronique et thermique dans des nanostructures." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS566/document.
The perpetual shrinking of microelectronic devices makes it crucial to have a proper understanding of transport mechanisms at the nanoscale. While simple effects are now well understood in homogeneous materials, the understanding of nanoscale transport in heterosystems needs to be improved. For instance, the relationship between current, resistance, and heat flux in nanostructures remains to be clarified. In this context, the subject of the thesis is centered around the development and application of advanced numerical methods used to predict electronic and thermal conductivities of nanomaterials. This manuscript is divided into three parts. We begin with the parameterization of a classical interatomic potential, suitable for the description of multicomponent systems, in order to model the structural, vibrational, and thermal transport properties of both silica and silicon. A well-defined, reproducible, and automated optimization procedure is derived. As an example, we evaluate the temperature dependence of the Kapitza resistance between amorphous silica and crystalline silicon, and highlight the importance of an accurate description of the structure of the interface. Then, we have studied thermal transport in graphene supported on amorphous silica, by evaluating the mode-wise decomposition of thermal conductivity. The influence of hydroxylation on heat transport, as well as the significant role played by collective excitations of phonons, have come to light. Finally, electronic transport properties of graphene supported on quasi-two-dimensional silica, a system recently observed experimentally, have been investigated. The influence on transport properties of ripples in the graphene sheet or in the substrate, which often occur in samples and whose amplitude and wavelength can be controlled, has been evaluated. We have also modeled electrostatic gating, and its impact on electronic transport
Hamzeh, Hani. "Résolution de l'équation de transport de Boltzmann pour les phonons et applications." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00778705.
Santamore, Deborah Hannah Cross Michael Clifford. "Quantum transport and dynamics of phonons in mesoscopic systems /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05272003-152136.
Sarrazin, Emmanuelle. "Etude du transport électronique dans un nanofil de silicium." Paris 11, 2009. http://www.theses.fr/2009PA112118.
Semiconductor nanowires have become in few years a subject of intense interest. These one-dimensional structures are considered as potential building blocks for nanoscale devices due to their promising electronic, optical and thermal properties, which differ from bulk properties. The knowledge of electron transport properties is essential to determine the performance of devices based on nanowires. This work aims to model the mobility of electrons in silicon nanowire. It is based on three points: electronic structure, scattering mechanisms and transport. A self-consistent Poisson-Schrödinger solver provides the band structure. The comparison between tight-binding method and effective mass approximation allows to discuss on the validity of effective mass approximation for thin nanowires. Then, scattering rates due to phonon scattering and surface roughness scattering are described using Fermi’s golden rule. Finally, both electron velocity and low-field electron mobility are computed with an ensemble Monte-Carlo method, which solves the Boltzmann transport equation. This approach leads to the understanding of the impact of electron and phonon confinement on transport properties and to evaluate the influence of scattering mechanisms on the mobility. The investigation of the impact of cross section size and gate bias shows a reduction of electron mobility with the decrease of cross section size and/or with the increase of gate bias whatever the scattering mechanisms taken into account
Eckold, Götz. "Time resolved phonons as a microscopic probe for solid state reactions." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186610.
Lee, Sangyeop. "Transport of phonons and electrons in thermoelectric materials and graphene." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100136.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 137-143).
Understanding transport of phonons and electrons plays a critical role in developing energy conversion and information devices. Thermoelectric materials, which directly convert heat to electricity or vice versa, require both extremely low thermal conductivity and high thermoelectric power factor. However, a good understanding of low thermal conductivity is still lacking even for several good thermoelectric materials that have been studied over several decades. For the information devices, graphene has recently drawn much attention for various applications including high speed transistors due to its high electron mobility and high thermal conductivity. However, the graphene's high thermal conductivity has yet to be fully understood. There have been many studies based on diffusive-ballistic phonon transport, but no conclusive explanation for the graphene's high thermal conductivity has been drawn. In this thesis, we investigate the transport of phonons and electrons in thermoelectric materials and graphene using both first principles calculations and experimental characterizations. We start by studying phonon transport in Bi and Bi-Sb alloys using first principles calculations. A notable observation from this calculation is that a strong long-range interaction exists in Bi and Sb along a specific crystallographic direction. We further show that this long-range interaction is also found in other good thermoelectric materials, and is a key to understanding their low thermal conductivity. The long-range interaction is explained with resonant bonding which many good thermoelectric materials commonly share. The particularly strong resonant bonding in group IV-VI materials leads to the low thermal conductivity through the long-range interaction and resulting softening of optical phonons that strongly scatter acoustic phonons. We study electron transport in thermoelectric materials with two-dimensional discontinuities, such as grain boundaries. We set up an experimental system to measure thermo- and galvano-magnetic electron transport coefficients of a Bi₂Te₂.₇Se₀.₃ nanocomposite sample to examine the electron filtering effect by many grain boundaries in the nanocomposite. The experimental results indicate that the nanocomposite sample exhibits the electron filtering effect and it would be possible to increase the thermoelectric power factor by engineering the potential barrier of grain boundaries. While thermoelectric applications require materials with low thermal conductivity, electronic and optoelectronic devices often require high thermal conductivity. Graphene is attractive for these applications because of its unique electrical, optical, and thermal properties. We use first-principles calculations to reveal that the phonon transport in graphene is not diffusive unlike many threedimensional materials, but is hydrodynamic due to graphene's two-dimensional features. The hydrodynamic phonon transport is demonstrated through a drift motion of phonons, phonon Poiseuille flow, and second sound, all of which are not possible in both diffusive and ballistic phonon transport.
by Sangyeop Lee.
Ph. D.
Jean, Valentin. "Modélisation du transport de phonons dans les semi-conducteurs nanostructurés." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0145/document.
Since the past decades, progresses in nanomaterials engineering raise new questions about heat transport processes at very short time and space scales. Thermal properties of nanoscaled devices are determined from the resolution of the Boltzmann Transport Equation (BTE) for phonons, which are the main heat carriers in semiconductors. In this study, BTE is solved with a numerical tool based on a statistical method (Monte Carlo) which tracks phonons’ motion in two kinds of nanostructures: nanofilms and nanowires. We focus on the effect of homogeneous and heterogeneous porous materials as well as nanowires with varying diameters. All these devices present interesting prospects regarding thermal conductivity reduction
Sundaresan, Sasi Sekaran. "ATOMISTIC MODELING OF PHONON BANDSTRUCTURE AND TRANSPORT FOR OPTIMAL THERMAL MANAGEMENT IN NANOSCALE DEVICES." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/dissertations/854.
Eckold, Götz. "Time resolved phonons as a microscopic probe for solid state reactions." Diffusion fundamentals 12 (2010) 19, 2010. https://ul.qucosa.de/id/qucosa%3A13871.
de, Tomás Andrés Carla. "On thermal transport by phonons in bulk and nanostructured semiconductor materials." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/285571.
The aim of this theoretical work is twofold. First, to contribute to a better understand- ing of phonon heat transport in bulk and nanostructured semiconductors, like thin-films or nanowires, in a wide range of temperatures, paying special attention to phonon-phonon col- lisions. Second, to improve the prediction capability of the thermal conductivity of the most common semiconductors. To achieve this, it becomes necessary the formulation of a new model allowing us to overcome the diculties associated to the existing models, with the aim to fulfill two desirable conditions: to provide a general expression for the thermal conduc- tivity, valid for several materials with di↵erent size-scales and geometries in a wide range of temperatures, and to have the smallest number of free adjustable parameters to assure the reliability of the model. The potentiality of such model would be to serve as a useful tool to design more ecient thermoelectric devices. The fruit of our study is the Kinetic-collective model which is developed in the framework of the Boltzmann transport equation as a natural generalization of the Guyer-Krumhansl model. Since phonon interactions are the source of thermal resistance, they deserve a special discussion in any thermal conductivity study. Precisely, the keystone in our work is the treatment of phonon-phonon collisions regarding their di↵erent nature. The prediction capability of the model need to be tested on several materials. In particular, we study five materials with thermoelectric interest. In first place, silicon, because it is an ideal test material due to the considerable amount of experimental data available in the literature, and because of its inherent scientific and technological importance. Secondly, we extend our study to other materials with the same lattice structure as silicon, that is the family of group IV element semiconductors (germanium, diamond, silicon and gray-tin), which also have been object of intense study, specially germanium, due to the recent and fast development of SiGe alloys and superlattices. Finally, we finish our study with a more complicated material regarding its lattice structure, bismuth telluride, which is known to be a very ecient thermoelectric material due to its high figure of merit. The Thesis is arranged in eight Chapters. The lay out is as follows: Chapter 1 con- textualizes the topic of the work and briefly introduces the basic physics related to phonon transport. In Chapter 2 the fundamental quantity necessary for considering any thermal property, the phonon dispersion relations, have been obtained for the materials under study. For this purpose, two lattice dynamics models are used: the Bond-charge model for group-IV semiconductors (silicon, germanium, diamond and gray-tin), and the Rigid-ion model for bismuth telluride (Bi2Te3). Along with their corresponding phonon dispersion relations, phonon density of states and specific heat results are also presented. The phonon relaxation times that suit these materials are discussed in Chapter 3, where new expressions to account for the phonon-phonon collisions are also presented. In the first part of Chapter 4 the most represen- tative thermal conductivity models to date are introduced and discussed, in the second part, a new model to predict the thermal conductivity, the Kinetic-collective model, is presented and its conceptual di↵erences and advantages with respect to previous similar models are discussed. In Chapter 5 the Kinetic-collective model is applied to silicon bulk samples with di↵erent isotopic composition and several nanostructured samples with di↵erent geometries (thin-films and nanowires) obtaining predictions for their thermal conductivity in a wide in- terval of temperatures. Some novel aspects of phonon transport arising from these results are discussed. In Chapter 6 the Kinetic-collective model is applied to the other group-IV materials using theoretical expressions to predict their relaxation times and, eventually, their thermal conductivity. Results for several samples with di↵erent isotopic compositions in a wide range of temperature are presented and discussed. In Chapter 7 the Kinetic-collective model is applied to Bi2Te3, providing thermal conductivity predictions for nanowires with several diameter values, and the results are discussed in view of possible applications in ther- moelectricity. Finally, in Chapter 8 the main conclusions of this Thesis are summarized and possible future lines of work stemming from its several results are discussed.
Latour, Benoit. "Contribution à l'étude du transport d'énergie dans la matière condensée : phonons, électrons et photons." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLC014/document.
Energy transport at the nanoscale involves different types of carriers - phonon, electron and photon. Their spatial confinement in nanostructured materials implies the invalidation of the macroscopic laws of heat transfer. Therefore, new mechanisms arise and lead to novel thermal properties. This manuscript is devoted to the study of phonon transport in nanomaterials as well as the dissipation processes involving photon/electron and electron/phonon interactions. It is divided in three independent parts. We have first investigated the wave properties of thermal phonons. We have developed a theory to quantitatively assess the coherence of these carriers. Then, we have adressed the coupling between plasmonics and phonon transport in metallic materials. The objective is to quantify how the heat generated by the absorption of an electromagnetic energy will impact the surrounding medium. In the last part, we have included the Bose-Einstein quantum statistics in Molecular Dynamics simulations in order to compute thermal properties of nanomaterials at low temperatures
Han, Haoxue. "Effect of phonon interference on the thermal conductivity and heat carriers." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLC002.
Wave interference of phonons can modify the phonon spectrum and thereby the group velocity and phonon population. These wave interferences allow the flow of thermal energy to be manipulated by controlling the materials lattice thermal conductivity and using thermal mirrors to reflect thermal phonons.The technological application of the phonon interference in materials, such as enhanced thermoelectric energy conversion and improved thermal insulation,has thrusted the exploration for highly efficient wave interference materials. First, we provide a new approach to demonstrate that heat in solids can be manipulated like light. We precisely control the heat flow by the atomic-scale phononic metamaterial, which contains deliberate flaws in the crystalline atomic lattice,channeling the heat through different phonon paths. Destructive interference between heat waves following different paths leads to the total reflection of the heat current and thus to the remarkable reduction in the material ability to conduct heat. By exploiting this destructive phonon interference, we model a very counter-intuitive possibility of thermal transport: more heat flow is blocked by the opening of the additional phonon channels. Our thermal metamaterial is a good candidate for high-fi nesse atomic-scale heat mirrors. We provide an important further insight into the coherent control of phonons which can be applied both to sound and heat propagation.Secondly, we introduce a novel ultra-compact nanocapacitor of coherent phonons formed by high-finesse interference mirrors based on atomic-scale semiconducto rmetamaterials. Our molecular dynamics simulations show that the nanocapacitor stores monochromatic terahertz lattice waves, which can be used for phonon lasing - the emission of coherent phonons. Either one- or two-color phonon lasing can be realized depending on the geometry of the nanodevice. The two-color regime of the interference cavity originates from different incidence-angle dependence of phonon wave packet transmission for two wave polarizations at the respective antiresonances. Coherent phonon storage can be achieved by cooling the nanocapacitor initially thermalized at room temperature or by the pump-probe technique. The line width narrowing and the computed relative phonon participation number confirm strong phonon confinement in the interference cavity by an extremely small amount of resonance defects. The emission of coherent terahertz acoustic beams from the nanocapacitor can be realized by applying tunable reversible stress which shifts the antiresonance frequencies.Finally, we investigate the role of two-path destructive phonon interference induced by long-range interatomic forces on the thermal conductance and conductivityof a silicon-germanium alloy by atomistic calculations. The thermal conductance across a germanium atomic plane in the silicon lattice is substantially reduced by the destructive interference of the nearest-neighbour phononpath with a direct path bypassing the defect atoms. Such an interference causes a fivefold reduction in the lattice thermal conductivity in a SiGe alloy at room temperature. We demonstrate the predominant role of harmonic phonon interferences in governing the thermal conductivity of solids by suppressing the inelastic scattering processes at low temperature. Such interferences provide a harmonic resistive mechanism to explain and control heat conduction through the coherent behaviours of phonons in solids
Moussavou, Manel. "Modélisation du transport quantique de transistors double-grille : influence de la contrainte, du matériau et de la diffusion par les phonons." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0353.
The transistor is the elementary brick of Integrated circuits found in all electronic devices. Years after years the microelectronic industry has enhanced the performances of integrated circuits (speed and energy consumption) by downscaling the transistor. Nowadays besides the transistor’s downscaling, other techniques have been considered to maintain this growth: they are called technological boosters. Mechanical strain or new material, such as germanium (Ge) and III-V semiconductors, to replace Silicon are example of technological boosters. By the means of numerical quantum simulations and modeling, this these work propose a study of the effect of technological boosters on the electric performances of the next generation of transistors
Lee, Youseung. "Traitement quantique original des interactions inélastiques pour la modélisation atomistique du transport dans les nano-structures tri-dimensionnelles." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0345.
Non-equilibrium Green’s function (NEGF) formalism during recent decades has attracted numerous interests for studying quantum transport properties of nanostructures and nano-devices in which inelastic interactions like electron-phonon scattering have a significant impact. Incorporation of inelastic interactions in NEGF framework is usually performed within the self-consistent Born approximation (SCBA) which induces a numerically demanding iterative scheme. As an alternative technique, we propose an efficient method, the so-called Lowest Order Approximation (LOA) coupled with the Pade approximants. Its main advantage is to significantly reduce the computational time, and to describe the electron-phonon scattering physically. This approach should then considerably extend the accessibility of using atomistic quantum transport codes to study three-dimensional (3D) realistic systems without requiring numerous numerical resources
Larroque, Jérôme. "Étude théorique de l'anisotropie du transport thermique dans des nanostructures à base de silicium et de germanium." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS001/document.
The heat transfer in semiconducting nanostructures is a current research topic, covering a wide range of applications including self-heating in nanoelectronic devices and energy conversion via thermoelectric effect. The modeling of heat transport at the nanometer scale is complex as the device length is in the same order of magnitude than the mean free path of heat carriers (phonons). The local pseudo-equilibrium assumption is no longer relevant, moreover confinement effects can also appear. Therefore development of specific modeling tools is highly desirable.To take into account the confinement effects, I have calculated the phonon dispersion relations in nanostructures. For this, I have implemented an atomistic semi-empirical method called ABCM (Adiabadic Bond Charge Model). I have calculated, in the entire Brillouin zone (Full Band approach), the dispersion relationship of phonons in both Silicon and Germanium for both Zinc-Blende and Wurtzite phases.In addition, to evaluate the thermal interface resistance, an original extension of the Acoustic Mismatch Model, completely full band, was developed. Within this approach, the dependence on the relative orientation of crystals has been studied in polytype nanowires that were recently synthesized in the laboratory.In parallel, to study the transport of phonons, I developed a particle Monte Carlo simulator that uses Full-Band dispersions calculated via ABCM. This kind of simulator is very versatile and can describe all transport regimes (from ballistic to diffusive one). Moreover, as it uses a "Full-Band" dispersion confinement effects can also be included. This simulator allowed me to study the effects of a change in orientation of the crystallographic planes on the thermal conductivity in both silicon and germanium nanowires. I have thus evaluated the anisotropy of the heat fluxes in these nanostructures
Sohier, Thibault. "Electrons et phonons dans le graphène : couplage électron-phonon, écrantage et transport dans une configuration type transistor à effet de champ." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066393/document.
Understanding the transport properties of two-dimensional crystals doped by field effect is a conceptual milestone for tomorrow's nanoelectronics. In this thesis we develop first-principles methods to investigate electron-phonon interactions, screening and phonon-limited transport in graphene. To overcome the limitations of existing plane-wave ab initio packages, originally devised for three-dimensional periodic solids, we truncate the Coulomb interaction in the third direction and isolate the 2D system from its periodic images. This is implemented in density-functional perturbation theory to calculate charge density responses and phonon spectra in a two-dimensional framework. We use those methods to develop a quantitative model of electron-phonon coupling for graphene in the field effect transistor configuration. We find that the coupling of electrons to acoustic phonons is dominated by the unscreened gauge field, which we compute with full inclusion of electron-electron interactions at the GW level. Our simulations of the static screening properties of graphene validate analytical models and reveal that the deformation potential is strongly screened, such that its contribution to acoustic phonon scattering is negligible. We find a small but finite linear coupling with out-of-plane phonons. By solving the Boltzmann transport equation we obtain the phonon-limited resistivity. Below room temperature, our results confirm the role of acoustic phonons and a 15% increase of the ab initio gauge field parameter leads to an excellent quantitative agreement with experiment. Above room-temperature, we point to the importance of the coupling with intrinsic optical phonons
Saci, Abdelhak. "Transport thermique dans les milieux nano-structurés (GaAs)n / (AlAs)n." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00825305.
Moussavou, Manel. "Modélisation du transport quantique de transistors double-grille : influence de la contrainte, du matériau et de la diffusion par les phonons." Electronic Thesis or Diss., Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0353.
The transistor is the elementary brick of Integrated circuits found in all electronic devices. Years after years the microelectronic industry has enhanced the performances of integrated circuits (speed and energy consumption) by downscaling the transistor. Nowadays besides the transistor’s downscaling, other techniques have been considered to maintain this growth: they are called technological boosters. Mechanical strain or new material, such as germanium (Ge) and III-V semiconductors, to replace Silicon are example of technological boosters. By the means of numerical quantum simulations and modeling, this these work propose a study of the effect of technological boosters on the electric performances of the next generation of transistors
Ramière, Aymeric. "Impact des rugosités sur le transport des phonons aux surfaces et interfaces à très basses températures." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112351/document.
This thesis aims at characterizing the thermal contact resistance at two interfaces of different nature. The first is a physical interface between Silicon(111) and superfluid Helium-4. The thermal contact resistance is evaluated experimentally for temperatures between 0.3K and 2.0K while varying pressure from the saturated vapor pressure to the Helium-4 solidification pressure (i.e. 25bars). Experimental results, analysed with Adamenko and Fuks model, show that nanoscale surface roughness governs heat transmission at this interface. Furthermore, a first order transition in the thermal contact resistance is revealed due to Helium-4 solidification. The second studied interface is an abrupt constriction created by a micro-junction between two suspended membranes. Even though there is no material discontinuity, Monte-Carlo numerical simulations show the existence of a thermal contact resistance between the membrane and the entrance of the junction. Using simulations we explore the effects of geometry and nanoscale surface roughness in bidimensional and tridimensional micro-structure
Lee, Youseung. "Traitement quantique original des interactions inélastiques pour la modélisation atomistique du transport dans les nano-structures tri-dimensionnelles." Electronic Thesis or Diss., Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0345.
Non-equilibrium Green’s function (NEGF) formalism during recent decades has attracted numerous interests for studying quantum transport properties of nanostructures and nano-devices in which inelastic interactions like electron-phonon scattering have a significant impact. Incorporation of inelastic interactions in NEGF framework is usually performed within the self-consistent Born approximation (SCBA) which induces a numerically demanding iterative scheme. As an alternative technique, we propose an efficient method, the so-called Lowest Order Approximation (LOA) coupled with the Pade approximants. Its main advantage is to significantly reduce the computational time, and to describe the electron-phonon scattering physically. This approach should then considerably extend the accessibility of using atomistic quantum transport codes to study three-dimensional (3D) realistic systems without requiring numerous numerical resources
Goldie, David John. "Quasiparticle and phonon transport in superconducting indium and quasiparticle trapping." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300128.
Alkurdi, Ali. "Transport Thermique aux Interfaces : Angle Critique des Phonons, Transfert à Travers un Gap; Transfert Autour d'une Nanoparticule Colloïdale Cœur-Coquille." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1197.
This thesis is devoted to the study of interfacial thermal transport at the nanoscale where Fourier’s law is not valid. This is because, at this scale, phonon mean free path becomes smaller to the characteristic length of the system, thus the heat transfer is no longer diffusive but rather ballistic. As a consequence, the thermal boundary resistance (TBR) becomes a determinant factor in heat transfer. The goal of this thesis is, firstly, to study phonon transmission and predict the thermal boundary conductance at interface between two solids. To this end, we have developed a new approach, which combines lattice dynamics calculations and inputs from ab initio, and we have applied our LD model to two types of solid structures: the face-centered cubic (FCC) crystal solid and the diamond-like crystal solid.Secondly, we aim to quantify the phononic contribution in heat transfer across a nanometric vacuum gap that separates two solids. We have used this ab initio LD model to predict the contribution of phonons in the heat transfer across a vacuum gap in two systems: the Au/vacuum-gap/Au and the Si/vacuum-gap/Si. Our results indicate that phonons do contribute significantly to heat transfer across a nanometric/subnanometric vacuum gap. Finally, we have investigated heat transfer in a system made of a core-shell nanoparticle (NP) immersed in water and heated by a laser pulse. We have used the four temperatures model, we have solved numerically the heat transfer equations in the system, taking into account the thermal boundary resistance (TBR) and the interfacial electron-phonon coupling
Terris, Damian Joulain Karl Lemonnier Denis. "Transfert de chaleur à échelles de temps et d'espace ultra-courtes simulation numérique pour des nanofils et nanofilms de semiconducteur /." Poitiers : I-Médias, 2008. http://08.edel.univ-poitiers.fr/theses/index.php?id=1924.
Seijas, Bellido Juan Antonio. "Computational studies of thermal transport in functional oxides." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669787.
This Thesis collects the computational works we have done in the field of condensed matter physics, focused on the thermal transport properties of the Lead Titanate (PbTiO3) and the Zinc Oxide (ZnO), both representative materials of many other insulating functional oxides. The first has been modeled using a second-principles potential, that is, a potential parameterized from first-principles calculations, which captures some quantum effects that can be relevant in the material. We have modeled the second one using the Buckingham's potential, a simple analytical expression that seems to describe the behavior of ZnO in a fairly approximate agreement with experiments.
Chapelon, Olivier. "Transport en régime de porteurs chauds dans le silicium de type n." Montpellier 2, 1993. http://www.theses.fr/1993MON20066.
Andrea, Luc. "Modélisation du transport thermique dans des matériaux thermoélectriques." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066122/document.
Thermoelectric materials provide a way to convert thermal energy into electrical energy. Nonetheless, their low efficiency is the main obstacle for global scale applications. Experimentally, specific treatments can lead to great improvement in the efficiency, mainly by lowering the thermal conductivity. This thesis is aimed at calculating from first principles, the thermal transport properties in perfect and doped half-Heusler thermoelectric materials. We begin with a theoretical analysis of the harmonic and anharmonic properties of phonons for perfect phases.The density functional theory is used to deduce the phonons lifetime from phonon-phonon interactions. The lifetimes are integrated into the Boltzmann transport equation for the phonon density, which solution allows us to compute fully ab initio the lattice thermal conductivity. The purpose of point defects is to scatter the phonons and thus reduce thermal conductivity. We developed two methods to account for the defects on thermal transport. The first one, based on a mean field approach, is suitable for the high concentration regimes. The second one in the framework of Green functions theory is used for dilute regimes. Both methods consistently show that the main reduction of thermal conductivity is already obtained within around 10 % of solute elements in NiTiSn, NiZrSn and NiHfSn
Maire, Jérémie. "Thermal phonon transport in silicon nanostructures." Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0044/document.
In the last two decades, nano-structuration has allowed thermoelectric efficiency to rise dramatically. Silicon (Si), originally a poor thermoelectric material, when scaled down, to form nanowires for example, has seen its efficiency improve enough to be accompanied by a renewed interest towards thermal transport in Si nanostructures. Although it is already possible to reduce thermal conductivity in Si nanostructures by nearly two orders of magnitude, thermal transport mechanisms remain unclear. A better understanding of these mechanisms could not only help to improve thermoelectric efficiency but also open up the path towards high-frequency thermal phonon control in similar ways that have been achieved with photons. The objective of this work was thus to develop a characterization platform, study thermal transport in various Si nanostructures, and ultimately highlight the contribution of the coherent phonon transport to thermal conductivity. First, we developed an optical characterization system alongside the fabrication process. Fabrication of the structures is realized on-site in clean rooms, using a combination of wet processes, electron-beam lithography, plasma etching and metal deposition. The characterization system is based on the thermoreflectance principle: the change in reflectivity of a metal at a certain wavelength is linked to its change in temperature. Based on this, we built a system specifically designed to measure suspended nanostructures. Then we studied the thermal properties of various kinds of nanostructures. Suspended unpatterned thin films served as a reference and were shown to be in good agreement with the literature as well as Si nanowires, in which thermal transport has been confirmed to be diffusive. Only at very low temperature and for short nanowires does a partially ballistic transport regime appear. While studying 1D periodic fishbone nanostructures, it was found that thermal conductivity could be adjusted by varying the shape which in turn impacts surface scattering. Furthermore, low temperature measurements confirmed once more the specularity of phonon scattering at the surfaces. Shifting the study towards 2D phononic crystals (PnCs), it was found that although thermal conductivity is mostly dominated by the surface-to-volume (S/V) ratio for most structures, when the limiting dimension, i.e. the inter-hole spacing, becomes small enough, thermal conductivity depends solely on this parameter, being independent of the S/V ratio. Lastly, we were able to observe, at low temperature in 2D PnCs, i.e. arrays of holes, thermal conduction tuning based on the wave nature of phonons, thus achieving the objective of this work
Andrea, Luc. "Modélisation du transport thermique dans des matériaux thermoélectriques." Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066122.
Thermoelectric materials provide a way to convert thermal energy into electrical energy. Nonetheless, their low efficiency is the main obstacle for global scale applications. Experimentally, specific treatments can lead to great improvement in the efficiency, mainly by lowering the thermal conductivity. This thesis is aimed at calculating from first principles, the thermal transport properties in perfect and doped half-Heusler thermoelectric materials. We begin with a theoretical analysis of the harmonic and anharmonic properties of phonons for perfect phases.The density functional theory is used to deduce the phonons lifetime from phonon-phonon interactions. The lifetimes are integrated into the Boltzmann transport equation for the phonon density, which solution allows us to compute fully ab initio the lattice thermal conductivity. The purpose of point defects is to scatter the phonons and thus reduce thermal conductivity. We developed two methods to account for the defects on thermal transport. The first one, based on a mean field approach, is suitable for the high concentration regimes. The second one in the framework of Green functions theory is used for dilute regimes. Both methods consistently show that the main reduction of thermal conductivity is already obtained within around 10 % of solute elements in NiTiSn, NiZrSn and NiHfSn
Lindsay, Lucas R. "Theory of Phonon Thermal Transport in Single-walled Carbon Nanotubes and Graphene." Thesis, Boston College, 2010. http://hdl.handle.net/2345/1167.
A theory is presented for describing the lattice thermal conductivities of graphene and single-walled carbon nanotubes. A phonon Boltzmann transport equation approach is employed to describe anharmonic phonon-phonon, crystal boundary, and isotopic impurity scattering. Full quantum mechanical phonon scattering is employed and an exact solution for the linearized Boltzmann transport equation is determined for each system without use of common relaxation time and long-wavelength approximations. The failures of these approximations in describing the thermal transport properties of nanotubes is discussed. An efficient symmetry based dynamical scheme is developed for carbon nanotubes and selection rules for phonon-phonon scattering in both graphene and nanotubes are introduced. The selection rule for scattering in single-walled carbon nanotubes allows for calculations of the thermal conductivities of large-diameter and chiral nanotubes that could not be previously studied due to computational limitations. Also due to this selection rule, no acoustic-only umklapp scattering can occur, thus, acoustic-optic scattering must be included in order to have thermal resistance from three-phonon processes. The graphene selection rule severely restricts phonon-phonon scattering of out-of-plane modes. This restriction leads to large contributions to the total thermal conductivity of graphene from the acoustic, out-of-plane modes which have been previously neglected. Empirical potentials used to model interactions in carbon-based materials are optimized to better describe the lattice dynamics of graphene-derived systems. These potentials are then used to generate the interatomic force constants needed to make calculations of the thermal conductivities of graphene and carbon nanotubes. Calculations of the thermal conductivities of single-walled carbon nanotubes and graphene for different temperatures and lengths are presented. The thermal conductivities of SWCNTs saturate in the diffusive regime when the effects of higher-order scattering processes are estimated and correctly reproduce the ballistic limit for short-length nanotubes at low temperatures. The effects of isotopic impurity scattering on the thermal conductivities of graphene and SWCNTs are explored. Isotopic impurities have little effect in the low (high) temperature regime where boundary (umklapp) scattering dominates the behavior of the thermal conductivities. In the intermediate temperature regime, modest reductions in the thermal conductivities, 15-20%, occur due to impurities. The thermal conductivities of a wide-range of SWCNTs are explored. The thermal conductivities of successively larger-diameter, one-dimensional nanotubes approach the thermal conductivity of two-dimensional graphene
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
Mittal, Arpit. "Prediction of Non-Equilibrium Heat Conduction in Crystalline Materials Using the Boltzmann Transport Equation for Phonons." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316471562.
Blanc, Christophe. "Nanoscale structuration effects on phonon transport at low temperatures." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY079/document.
This PhD entitled "Nanoscale structuration effect on the phonon transport at low temperature" take place for three years in the Thermodynamique et Biophysique des Petits Systèmes of the Institut Néel.The context of this PhD is to understand and control the heat transport in samples with variations at the nanoscale. These samples were mostly suspended silicon nanowires. The production was performed in the Néel Institute. During these three years, three important results have been demonstrated.First, we verify that heat transport is not dominated by an effect due to the contact between the suspended nanowire and the thermal bath. This has been demonstrated by the agreement between the measurements and the model called Casimir-Ziman. It was also mainly verified with wires whose junction to the thermal bath has been adapted to allow transmission close to unity. These profiles nanowires have the same thermal conductance as a nanowire with abrupt junction to the thermal bath. This proves that the transmission is always close to 1.Then measurements on nanowires whose section is corrugated have shown a reduction in thermal conductance. This reduction is explained by the presence of backscatter phonons at the surface, resulting in a large reduction of their mean free path. Thus, the phonons in a smooth nanowire have a mean free path up to 9 times greater than in these corrugated nanowires. Simulations with the Monte-Carlo method also demonstrate this effect.If these first results were achieved for monocrystalline silicon nanowires, my last work has focused on the study sample of silicon nitride. This material is an amorphous one. Physics of heat transport in amorphous materials is not yet fully understood. However, measurements on these materials show a similar behavior, both qualitatively and quantitatively, for almost all amorphous materials. We have measured samples of different kinds, to see if this behavior was still valid when the sample size is reduced. The result of our measurements is that the size plays a role in transport. As in crystalline materials, the small sample size will limit the heat transport. However transport in low-dimensional samples shows the same behavior qualitatively as in bulk amorphous materials. This can help provide clues for understanding the heat transport in amorphous materials.In conclusion, this work has allowed me to make and measure the heat transport in different types of samples. The results allow a better knowledge of the phonon transport, thus helping to pave the way towards a better control of heat transport
Hützen, Roland [Verfasser], Reinhold [Akademischer Betreuer] Egger, and Jürgen [Akademischer Betreuer] Horbach. "Transport through interacting quantum dots with Majorana fermions or phonons / Roland Hützen. Gutachter: Reinhold Egger ; Jürgen Horbach." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2013. http://d-nb.info/1041322119/34.
Brendel, Christian [Verfasser], Florian [Akademischer Betreuer] Marquardt, and Kai Phillip [Gutachter] Schmidt. "Topologically Protected Transport of Phonons at the Nanoscale / Christian Brendel ; Gutachter: Kai Phillip Schmidt ; Betreuer: Florian Marquardt." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2019. http://d-nb.info/1192512766/34.
Ezzahri, Younès. "Etude du transport des phonons dans les micro-réfrigérateurs à base de super-réseaux Si/Si/Ge." Bordeaux 1, 2005. http://www.theses.fr/2005BOR13090.
Terris, Damian. "Transfert de chaleur à échelles de temps et d'espace ultra-courtes : simulation numérique pour des nanofils et nanofilms de semiconducteur." Poitiers, 2008. http://theses.edel.univ-poitiers.fr/theses/2008/Terris-Damian/2008-Terris-Damian-These.pdf.
Since high technology progress decreases system dimensions, it is necessarily to understand their physical properties. Therefore, this work contributes in the thermal property knowledge. Numerical simulations are then done to predict heat transfer. To achieve this request, Boltzmann transfer equation is solved, using the discrete ordinate method. Since nanowires and nanofilms are frequently found in microelectronics, their geometries are studied. Furthermore, heat carrier spectral dependence is taken into account trough their velocities and relaxation times. In a first hand, steady state results are used to define thermal properties. It is shown that, in nanowires, diffusive regime is always observed whereas, in films, Fourier’s law can only be used for thickness greater than 1 m, at ambient temperature. For lower temperatures or thicknesses, heat transfers are governed by ballistic phenomena. Finally, taken into account spectral dependences allow us to predict heat transfer at small time scales. It is then viewed that conduction heat transfers in ballistic regime have two temperature waves due to phonon polarizations
Chauhan, Vinay Singh. "Impact of Nanoscale Defects on Thermal Transport in Materials." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586440154974469.
He, Fei. "Microscopic approach to the thermal transport in model non conducting oxides under extreme conditions." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS568.
Lattice dynamics and vibrational properties of materials at low and moderate temperatures can be, in most of the cases, accurately explained on the basis of an harmonic model, which assumes that phonons are independent of each other. However, at high temperatures this model finds its limitations, as the coupling between phonons become increasingly important. An improved understanding of the anharmonic interactions between lattice modes not only has a fundamental interest, but is also necessary on a more applied basis, as phonons play a major role in many physical properties such as thermal and electrical conductivity, or superconductivity. This thesis aims at investigating the anharmonic lattice dynamics of magnesium oxide (MgO) as a function of pressure and temperature, considering up to three-phonons scattering processes. Phonon energies and line widths will be discussed in relation to the dielectric and thermal transport properties. The simple rock-salt structured MgO represents a first ideal target for both experiments and calculations, with the further advantage of being of primary interest in geoscience, being an archetypal mineral for planetary mantles. We combined infrared spectroscopy and inelastic X-ray scattering measurements to probe phonon energies and line widths across the entire Brillouin zone. Results of high-pressure and high-temperature experiments are complemented by density functional perturbation theory calculations. The direct comparison of measurements and calculations allows to get insight on the anharmonic dynamics of the system and to test the validity of the theoretical approach
Park, Junbum. "Monte Carlo simulations of phonon transport in nanostructures based on ab-initio methods." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST068.
As the trend towards miniaturization of electronic devices continues, understanding heat transport at the nanoscale becomes increasingly crucial for developing energy-efficient and reliable systems. Conventional Fourier's law fails to capture the complex dynamics of phonon-based heat transport in such miniaturized devices. With the drive for more compact and high-performance devices, exploring alternative materials beyond silicon is equally essential, focusing on their thermal properties. In this thesis, we study the phonon transport within nanostructures employing stochastic Monte Carlo (MC) methods. The accuracy of the simulations is enhanced by utilizing full band material description derived from ab-initio calculations based on density functional theory (DFT) without reliance on empirical parameters. This methodological approach allows for precise phonon scattering calculations across a broad temperature range of 0.1 to 1000 K, incorporating normal, Umklapp, and isotope scattering mechanisms to account for anharmonic interactions. We focus on examining alternative materials, such as gallium arsenide (GaAs) and two-dimensional (2D) materials like graphene, hexagonal boron nitride (h-BN), and transition metal dichalcogenides (TMDCs), each selected for their unique thermal properties. This thesis presents a comprehensive theoretical background on DFT, emphasizing the importance of anharmonic effects in phonon transport, and discusses the Monte Carlo algorithms for solving the Boltzmann transport equation. The results presented in this thesis include a thorough analysis of the thermal properties of GaAs nanostructures and their response to varying boundary conditions, device dimensions, and temperatures. Furthermore, we explore the thermal properties of 2D materials and their lateral heterostructures, assessing their interface thermal conductance (ITC) and the variation of phonon modal contributions near the interface. Employing the concept of directional temperature, the study provides precise ITC calculations, thereby elucidating the intricate thermal dynamics within these heterostructures. Finally, we investigate the transient thermal response in 100 nm long 2D h-BN/graphene lateral heterostructures. Through positional mapping and temporal response characterization, we provide a detailed understanding of the transient thermal behavior within these nanostructures. This work not only offers substantial contributions to the field of thermal transport in nanostructures but also opens new pathways for the design and application of advanced materials in electronics
Wu, Yunhui. "Experimental Investigation of Size Effects on Surface Phonon Polaritons and Phonon Transport." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC012/document.
Thermal conduction becomes less efficient as structures scale down into submicron sizes since phonon-boundary scattering becomes predominant and impede phonons more efficiently than Umklapp scattering. Recent studies indicated that the surface phonon polaritons (SPhPs), which are the evanescent electromagnetic waves generated by the hybridation of the optical phonons and the photons and propagating at the surface of a polar dielectric material surface, potentially serve as novel heat carriers to enhance the thermal performance in micro- and nanoscale devices. We study the condition of SPhPs existing in a dielectric submicron film with a broad frequency range. The calculaton of SPhPs thermal conductivity based on Boltzmann transport equation (BTE) demonstrates that the heat flux carried by SPhPs exceeds the one carried by phonons. We also conduct a time-domain-thermal-reflectance (TDTR) measurement of $SiN$ submicron films and demonstrate that the thermal conductivity due to the SPhPs at high temperatures increases by decreasing the film thickness. The results presented in this thesis have potential applications in the field of heat transfer, thermal management, near-field radiation and polaritonics
Mazzamuto, Fulvio. "Etude théorique des propriétés thermiques et thermoelectriques des nanorubans de graphène." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00652733.
Aristone, Flavio. "Contribution à l'étude des processus de diffusion sur les propriétés de transport vertical par minibande." Toulouse, INSA, 1994. http://www.theses.fr/1994ISAT0029.
Arabshahi, Hadi. "Simulations of electron transport in GaN devices." Thesis, Durham University, 2002. http://etheses.dur.ac.uk/4119/.
Randrianalisoa, Jaona Harifidy Baillis Dominique. "Transfert thermique par rayonnement et conduction dans les matériaux poreux micro et nanostructurés analogie transfert de phonons et de photons /." Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?id=randrianalisoa.