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Previous issue date: 2014-10-31 / CAPES / Understanding the structural properties of dislocations is essential since these defects govern the processes plastic deformation of materials. Particularly in semiconductors, these studies are important given the relevance of these materials for microelectronics. In this work, our focus will be the 90o partial dislocations in silicon. For the theoretical study of atomic-scale crystal dislocations, we use simulations based on semi-empirical quantum-mechanical methods closely linked to the tight-binding treatment, since it considers in its formulation that crystalline electronic states can be described in terms of atomic orbitals: Density Matrix Method Tight-Binding Order-N (DMTB). This method has a low computational cost which allows us to work with very large systems atoms in structures representation -including thousands of sites. In short, we describe how to produce and represent the 90o partial dislocations in Si, we consider three models for its core structure: a unreconstructed where the atoms have an almost fivefold coordination; a model reconstructed with period equal to the perfect lattice; and a model with twice period comparing with the perfect lattice. Finally, we calculate the range in energy of the system with the distance between the dislocations and the free surface of Si. / Compreender as propriedades estruturais de discord?ncias cristalinas ? fundamental uma vez que estes defeitos governam os processos de deforma??o pl?stica em materiais. Particularmente em semicondutores, esses estudos s?o importantes dada a relev?ncia desses materiais para a microeletr?nica. Neste trabalho nosso foco ser?o as discord?ncias cristalinas parciais a 90o em sil?cio. Para o estudo te?rico em escala at?mica das discord?ncias cristalinas, usamos simula??es baseadas em metodologias quanto-mec?nicas semi-emp?ricas atrav?s de um m?todo intimamente ligado ao tratamento tight-binding, uma vez que considera em sua formula??o que os estados eletr?nicos cristalinos podem ser descritos em termos de orbitais at?micos: M?todo da Matriz Densidade Tight-Binding de Ordem-N (DMTB). Este m?todo tem um custo computacional baixo o que permite que trabalhemos com sistemas muito grandes de ?tomos na representa??o das estruturas ? com milhares de s?tios inclusive. Em suma, descrevemos como produzir e representar as discord?ncias parciais a 90o em Si consideramos tr?s modelos para sua estrutura de caro?o: um n?o reconstru?do onde os ?tomos possuem uma coordena??o quase qu?ntupla; um modelo reconstru?do com per?odo igual ao per?odo da rede perfeita; e um modelo com per?odo dobrado em rela??o ao da rede perfeita. Por fim, calculamos a varia??o da energia do sistema com a dist?ncia entre as discord?ncias e a superf?cie livre do Si.
| Identifer | oai:union.ndltd.org:IBICT/oai:localhost:jspui/2091 |
| Date | 31 October 2014 |
| Creators | OLIVEIRA, Arnaldo Cesar Almeida |
| Contributors | Ara?jo, Mois?s Monteiro de, Oliveira, Clarissa de, Ara?jo, Mois?s Monteiro de, Bauerfeldt, Glauco Favilla, Silva, Alexandre Pinheiro da |
| Publisher | Universidade Federal Rural do Rio de Janeiro, Programa de P?s-Gradua??o em Modelagem Matem?tica e Computacional, UFRRJ, Brasil, Instituto de Ci?ncias Exatas |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da UFRRJ, instname:Universidade Federal Rural do Rio de Janeiro, instacron:UFRRJ |
| Rights | info:eu-repo/semantics/openAccess |
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