Escala da rugosidade e estrutura polimérica em um modelo de deposição, difusão e polimerização

• Ano de defesa: 2010
• Autor(a) principal: Euzébio, Jônatas Araújo Ribeiro
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Programa de Pós-graduação em Física; Física
• Palavras-chave em Português: Polimerização; Filme fino; Rugosidade (Superfície); CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: https://app.uff.br/riuff/handle/1/19122

Chemical vapor deposition polymerization (CVDP) has advantages over the preparation methods in solution. This polymer films growth technique requires no catalyst, solvent, or initiator, thus avoiding undesired materials in the final sample, and can produce conformal coatings of micro and nanostructures. These features give rise to different applications, thus it attracted increasing interest in the last years. We study a model for growth of polymer films using numerical simulations and scaling concepts. During the deposition, each new monomer ows in a direction perpendicular to the substrate, aggregates at the first contact with the deposit and executes up to G steps along the polymers, propagating an existing chain or nucleating a new polymer. Some qualitative results agree with those of a previous model for CVDP with collective diffusion, such as the roughness increase and density decrease with G. This supports the interpretation of G as a ratio between diffusion coeficient and monomer ux. We perform a systematic study of scaling properties of the surface roughness and of polymer size and shape. For large G, the polymers are stretched in the direction perpendicular to the substrate and have typical size increasing as G1=2. This is explained by the solution of the problem of random walk trapping, which illustrates the connection of surface processes and bulk properties. The distributions of polymer sizes are monotonically decreasing for all G and very broad, thus a large number of small chains and of chains much larger than the average is found in typical samples. The surface roughness obeys Kardar-Parisi-Zhang scaling, in contrast to the apparent anomalous scaling of previous CVDP models with oblique monomer ux. However, the calculation of reliable exponents requires accounting for huge finite-size corrections. Possible applications and extensions of this model are discussed.