Propriedades elétricas e térmicas em materiais bidimensionais
Autor(a) principal: | |
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Data de Publicação: | 2022 |
Tipo de documento: | Tese |
Idioma: | por |
Título da fonte: | Biblioteca Digital de Teses e Dissertações da UFPB |
Texto Completo: | https://repositorio.ufpb.br/jspui/handle/123456789/27253 |
Resumo: | With the synthesis of graphene in the laboratory and advances in research into new two-dimensional materials, the control of electrical and thermal conduction is essential for the development of new technologies. Thus, we investigated the electrical properties such as conductance and the effects of spin-orbit interaction in topological insulators and the effects of the presence of defects, such as the grains that are produced in the growths of polycrystalline samples, on the thermal conductivity, which are of crucial importance in the construction and enhancement of new devices. For this purpose, this thesis was divided into two parts. In the first one, we investigate the electrical transport in quasi-one-dimensional graphene nanoribbons that have a crystal lattice described by two overlapping triangular lattices, and therefore it has what we call sublattice symmetry that is related to the chirality sign that is studied in the random matrix theory ensembles. For this, we used the tight binding method to analyze graphene from three Hamiltonian models and measure the electrical conductance in different scenarios, as a function of energy, disorder force and magnetic flux. Consequently, it was possible to demonstrate that all models present the chirality sign, which is a result of great importance in the study of strongly correlated systems. Furthermore, through the maximum entropy principle we measure the correlation length via peak density, that is, we only count the number of conductance maxima in a given range of magnetic flux, confirming that such relevant quantity in the experimental area can be determined through a single realization. In the second part of the thesis, we explore the thermal properties of pristine and polycrystalline silicene. The systems were modeled using molecular dynamics and lattice dynamics to compute thermal conductivity, phonon state density and phonon dispersion relation. The results predict that the intrinsic thermal conductivity of 9.47 W/mK and an effective mean free path of 11.54 nm for the pristine silicene, however, as expected, in the polycrystalline samples the values of the thermal conductivities decrease as the effective grain sizes decrease or with increasing temperature. And the density of phonon states showed that low-frequency heat carriers are responsible for the change in thermal conductivity. In addition, the thesis contains the theoretical foundations of all the techniques used, as well as all the details to carry out the simulations. |
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Propriedades elétricas e térmicas em materiais bidimensionaisFísica - GrafenoSilicenoCondutância elétricaCondutividade térmicaPhysics - GrapheneSiliceneElectrical conductanceThermal conductivityCNPQ::CIENCIAS EXATAS E DA TERRA::FISICAWith the synthesis of graphene in the laboratory and advances in research into new two-dimensional materials, the control of electrical and thermal conduction is essential for the development of new technologies. Thus, we investigated the electrical properties such as conductance and the effects of spin-orbit interaction in topological insulators and the effects of the presence of defects, such as the grains that are produced in the growths of polycrystalline samples, on the thermal conductivity, which are of crucial importance in the construction and enhancement of new devices. For this purpose, this thesis was divided into two parts. In the first one, we investigate the electrical transport in quasi-one-dimensional graphene nanoribbons that have a crystal lattice described by two overlapping triangular lattices, and therefore it has what we call sublattice symmetry that is related to the chirality sign that is studied in the random matrix theory ensembles. For this, we used the tight binding method to analyze graphene from three Hamiltonian models and measure the electrical conductance in different scenarios, as a function of energy, disorder force and magnetic flux. Consequently, it was possible to demonstrate that all models present the chirality sign, which is a result of great importance in the study of strongly correlated systems. Furthermore, through the maximum entropy principle we measure the correlation length via peak density, that is, we only count the number of conductance maxima in a given range of magnetic flux, confirming that such relevant quantity in the experimental area can be determined through a single realization. In the second part of the thesis, we explore the thermal properties of pristine and polycrystalline silicene. The systems were modeled using molecular dynamics and lattice dynamics to compute thermal conductivity, phonon state density and phonon dispersion relation. The results predict that the intrinsic thermal conductivity of 9.47 W/mK and an effective mean free path of 11.54 nm for the pristine silicene, however, as expected, in the polycrystalline samples the values of the thermal conductivities decrease as the effective grain sizes decrease or with increasing temperature. And the density of phonon states showed that low-frequency heat carriers are responsible for the change in thermal conductivity. In addition, the thesis contains the theoretical foundations of all the techniques used, as well as all the details to carry out the simulations.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESCom a síntese do grafeno em laboratório e os avanços nas pesquisas em novos materiais bidimensionais o controle da condução elétrica e térmica são essenciais para o desenvolvimento de novas tecnologias. Assim, investigamos as propriedades elétricas como a condutância e os efeitos da interação spin órbita em isolantes topológicos e os efeitos da presença de defeitos, como os grãos que são produzidos nos crescimentos de amostras policristalinas, sobre a condutividade térmica que são de cruciais importância na construção e aprimoramento de novos dispositivos. Com esse intuito a presente tese foi dividida em duas partes. Na primeira, investigamos o transporte elétrico em nanofitas quasi-unidimensionais de grafeno que possuí uma rede cristalina descrita por duas redes triangulares sobrepostas, e por isso ela tem o que chamamos de simetria de sub-rede que está relacionado ao sinal da quiralidade que é estudada nos ensembles da teoria das matrizes aleatórias. Para isso utilizamos o método da ligação forte para analisar o grafeno a partir de três modelos de hamiltonianos e medir a condutância elétrica em diferentes cenários, como em função da energia, da força de desordem e do fluxo magnético. Consequentemente, foi possível demonstrar que todos os modelos apresentam o sinal da quiralidade o qual é um resultado de grande importância no estudo de sistemas fortemente correlacionados. Além do mais, através do princípio de máxima entropia medimos o comprimento de correlação via densidade de picos, ou seja, apenas contamos o número de máximos da condutância em um determinado intervalo de fluxo magnético, confirmando que tal quantidade relevante na área experimental pode ser determinada por meio de uma única realização. Na segunda parte da tese, exploramos as propriedades térmica do siliceno sem defeitos e policristalino. Os sistemas foram modelos usando dinâmica molecular e dinâmica de rede para computar a condutividade térmica, a densidade de estados dos fônons e a relação de dispersão dos fônons. Os resultados preveem que a condutividade térmica intrínseca de 9,47 W/mK e um livre caminho médio efetivo de 11,54 nm para o siliceno sem defeitos, porém, como esperado, nas amostras policristalinas os valores das condutividades térmicas diminuem à medida que os tamanhos efetivos dos grãos diminuem ou com o aumento da temperatura. E a densidade de estados dos fônons mostrou que os portadores de calor de baixas frequências são os responsáveis pela alteração da condutividade térmica. Em adicional, na tese encontra-se a fundamentação teóricas de todas as técnicas utilizadas, bem como todos os detalhes para realizar as simulações.Universidade Federal da ParaíbaBrasilFísicaPrograma de Pós-Graduação em FísicaUFPBRamos, Jorge Gabriel Gomes de Souzahttp://lattes.cnpq.br/4289978259221930Sá, Louis Gustavo da Costa Sobral e2023-06-27T16:03:00Z2022-10-112023-06-27T16:03:00Z2022-05-27info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesishttps://repositorio.ufpb.br/jspui/handle/123456789/27253porAttribution-NoDerivs 3.0 Brazilhttp://creativecommons.org/licenses/by-nd/3.0/br/info:eu-repo/semantics/openAccessreponame:Biblioteca Digital de Teses e Dissertações da UFPBinstname:Universidade Federal da Paraíba (UFPB)instacron:UFPB2023-06-28T06:04:24Zoai:repositorio.ufpb.br:123456789/27253Biblioteca Digital de Teses e Dissertaçõeshttps://repositorio.ufpb.br/PUBhttp://tede.biblioteca.ufpb.br:8080/oai/requestdiretoria@ufpb.br|| diretoria@ufpb.bropendoar:2023-06-28T06:04:24Biblioteca Digital de Teses e Dissertações da UFPB - Universidade Federal da Paraíba (UFPB)false |
dc.title.none.fl_str_mv |
Propriedades elétricas e térmicas em materiais bidimensionais |
title |
Propriedades elétricas e térmicas em materiais bidimensionais |
spellingShingle |
Propriedades elétricas e térmicas em materiais bidimensionais Sá, Louis Gustavo da Costa Sobral e Física - Grafeno Siliceno Condutância elétrica Condutividade térmica Physics - Graphene Silicene Electrical conductance Thermal conductivity CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
title_short |
Propriedades elétricas e térmicas em materiais bidimensionais |
title_full |
Propriedades elétricas e térmicas em materiais bidimensionais |
title_fullStr |
Propriedades elétricas e térmicas em materiais bidimensionais |
title_full_unstemmed |
Propriedades elétricas e térmicas em materiais bidimensionais |
title_sort |
Propriedades elétricas e térmicas em materiais bidimensionais |
author |
Sá, Louis Gustavo da Costa Sobral e |
author_facet |
Sá, Louis Gustavo da Costa Sobral e |
author_role |
author |
dc.contributor.none.fl_str_mv |
Ramos, Jorge Gabriel Gomes de Souza http://lattes.cnpq.br/4289978259221930 |
dc.contributor.author.fl_str_mv |
Sá, Louis Gustavo da Costa Sobral e |
dc.subject.por.fl_str_mv |
Física - Grafeno Siliceno Condutância elétrica Condutividade térmica Physics - Graphene Silicene Electrical conductance Thermal conductivity CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
topic |
Física - Grafeno Siliceno Condutância elétrica Condutividade térmica Physics - Graphene Silicene Electrical conductance Thermal conductivity CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
description |
With the synthesis of graphene in the laboratory and advances in research into new two-dimensional materials, the control of electrical and thermal conduction is essential for the development of new technologies. Thus, we investigated the electrical properties such as conductance and the effects of spin-orbit interaction in topological insulators and the effects of the presence of defects, such as the grains that are produced in the growths of polycrystalline samples, on the thermal conductivity, which are of crucial importance in the construction and enhancement of new devices. For this purpose, this thesis was divided into two parts. In the first one, we investigate the electrical transport in quasi-one-dimensional graphene nanoribbons that have a crystal lattice described by two overlapping triangular lattices, and therefore it has what we call sublattice symmetry that is related to the chirality sign that is studied in the random matrix theory ensembles. For this, we used the tight binding method to analyze graphene from three Hamiltonian models and measure the electrical conductance in different scenarios, as a function of energy, disorder force and magnetic flux. Consequently, it was possible to demonstrate that all models present the chirality sign, which is a result of great importance in the study of strongly correlated systems. Furthermore, through the maximum entropy principle we measure the correlation length via peak density, that is, we only count the number of conductance maxima in a given range of magnetic flux, confirming that such relevant quantity in the experimental area can be determined through a single realization. In the second part of the thesis, we explore the thermal properties of pristine and polycrystalline silicene. The systems were modeled using molecular dynamics and lattice dynamics to compute thermal conductivity, phonon state density and phonon dispersion relation. The results predict that the intrinsic thermal conductivity of 9.47 W/mK and an effective mean free path of 11.54 nm for the pristine silicene, however, as expected, in the polycrystalline samples the values of the thermal conductivities decrease as the effective grain sizes decrease or with increasing temperature. And the density of phonon states showed that low-frequency heat carriers are responsible for the change in thermal conductivity. In addition, the thesis contains the theoretical foundations of all the techniques used, as well as all the details to carry out the simulations. |
publishDate |
2022 |
dc.date.none.fl_str_mv |
2022-10-11 2022-05-27 2023-06-27T16:03:00Z 2023-06-27T16:03:00Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
format |
doctoralThesis |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
https://repositorio.ufpb.br/jspui/handle/123456789/27253 |
url |
https://repositorio.ufpb.br/jspui/handle/123456789/27253 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.rights.driver.fl_str_mv |
Attribution-NoDerivs 3.0 Brazil http://creativecommons.org/licenses/by-nd/3.0/br/ info:eu-repo/semantics/openAccess |
rights_invalid_str_mv |
Attribution-NoDerivs 3.0 Brazil http://creativecommons.org/licenses/by-nd/3.0/br/ |
eu_rights_str_mv |
openAccess |
dc.publisher.none.fl_str_mv |
Universidade Federal da Paraíba Brasil Física Programa de Pós-Graduação em Física UFPB |
publisher.none.fl_str_mv |
Universidade Federal da Paraíba Brasil Física Programa de Pós-Graduação em Física UFPB |
dc.source.none.fl_str_mv |
reponame:Biblioteca Digital de Teses e Dissertações da UFPB instname:Universidade Federal da Paraíba (UFPB) instacron:UFPB |
instname_str |
Universidade Federal da Paraíba (UFPB) |
instacron_str |
UFPB |
institution |
UFPB |
reponame_str |
Biblioteca Digital de Teses e Dissertações da UFPB |
collection |
Biblioteca Digital de Teses e Dissertações da UFPB |
repository.name.fl_str_mv |
Biblioteca Digital de Teses e Dissertações da UFPB - Universidade Federal da Paraíba (UFPB) |
repository.mail.fl_str_mv |
diretoria@ufpb.br|| diretoria@ufpb.br |
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1801843011291709440 |