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Master's Dissertation
DOI
10.11606/D.43.2009.tde-29052009-215819
Document
Author
Full name
Rodrigo Ramos da Silva
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2009
Supervisor
Committee
Caldas, Marilia Junqueira (President)
Justo Filho, Joao Francisco
Salvadori, Maria Cecilia Barbosa da Silveira
Title in Portuguese
Estudo teórico do comportamento térmico de superfícies de diamante(100) monohidrogenadas
Keywords in Portuguese
dinâmica molecular
Superfícies semicondutoras
tight binding
Abstract in Portuguese
Utilizando a Dinâmica Molecular Tight Binding (TBMD), parametrizada para sistemas de carbono e hidrogênio, simulamos com condições periódicas de contorno e modelos de fatia, superfícies de diamante (100) puras e hidrogenadas em modelos de reconstruções ideais usualmente presentes na literatura, analisando o seu comportamento geométrico e eletrônico. Em seguida abordamos o comportamento morfológico e eletrônico, em simulações com temperaturas que variam entre 100K e 2000K de dois modelos de superfícies monohidrogenadas, que apresentam dois domínios em torno de uma estrutura de depressão local, característica de filmes de alta rugosidade. Em oposição à grande estabilidade térmica exibida pelo modelo monohidrogenado ideal e pelas colunas contínuas de dímeros, os modelos com depressão apresentaram significativa migração de átomos de hidrogênio para regiões subsuperficiais. Em nossas simulações os átomos de hidrogênio ficaram confinados nas regiões subsuperficiais, introduzindo uma desordem morfológica na superfície e nas regiões internas à fatia, induzindo estados eletrônicos nesta região, que levam ao fechamento do gap, passando a caracterizar uma fase quase-metálica.
Title in English
Theoretical study of the thermal behavior of (100) monohydrogenated diamond surfaces
Keywords in English
molecular dynamics
Semiconducting surfaces
tight bindind.
Abstract in English
By using the Tight Binding Molecular Dynamics (TBMD), parametrized to describe carbon and hydrogen atoms composed of systems, we apply periodic boundary conditions, slab models in order to simulate (100) clean and hydrogenated diamond surfaces. We study first the standard models used in the literature, analyzing their geometrical and eletronic behavior. We then focus on the morphological and electronic properties, in simulations under finite temperature dynamics ranging from 100K up to 2000K, of two distinct models of monohydride surfaces; Each model exhibits two distincts domains in the surface pattern characterized by a local depression, characteristic of rough surfaces. In opposition to the high thermal stability observed for ideal monohydrogenated surfaces and the extended dimer rows, these models showed an expressive hydrogen migration to the subsurface regions. In our simulations the hydrogen atoms remain in the subsurface regions, but introduce morphological disorder at the surface and in the slab internal regions. These hydrogen atoms induce electronic states mostly localized in the subsurface region, which are responsible for closing the gap, and leading the system to exhibit a quasi-metallic phase.
 
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Publishing Date
2009-06-22
 
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