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Previous issue date: 2015-03-30 / In this study the spatial confinement effects on the topological (mass transport
and particle ejection) and chemical modifications of poly(methyl methacrylate) thin
films (1<?<360 nm) irradiated by swift heavy ions were systematically investigate. The
surface tracks dimensions were characterized by atomic force microscopy and the
results show that the surface effects are weakened when the length of the ion track is
spatially confined down to few nanometers. The deviation from bulk-like behavior starts
at a critical thickness ?1 as large as ~40 nm to the ridge volume, due to effects
associated to cooperative action of excited material along the track. However, ?1 is
much smaller for effects related to events close to the surface, such as the crater size
(?1~10 nm). Analytical calculations based on the pressure pulse model were carried
out to investigate theoretical aspects of the ion-matter energy transfer in the transport
and dissipation of the deposited energy. The results obtained from these calculations
match the experimental observations. Chemical modifications were investigated by
quantifying bond breaking rates, extracted by x-ray photoelectron spectroscopy. Cross
sections for carbon-oxygen bonds for films under Bi irradiation are slightly smaller for
thinner films, whilst for proton irradiation the values do not show substantial difference
down to the smallest thickness viable for analysis (?~5 nm). From these set of data it
is verified that the ionic irradiation effects on polymer thin films are weakened under
spatial confinement into layers with ? below a certain critical value ?1, dependent on
the probed effect. Substantial difference on the surface track dimensions were not
observed between the distinct substrates investigated. / Neste trabalho foram investigados sistematicamente os efeitos de
confinamento espacial nas modifica??es topol?gicas (transporte de massa e eje??o
de part?culas) e qu?micas induzidas por ?ons pesados de alta energia (de dezenas a
milhares de MeV) em filmes finos de poli(metacrilato de metila) (1< ? <360 nm). As
dimens?es dos efeitos de superf?cie induzidos pela irradia??o foram caracterizadas
por microscopia de for?a at?mica e os resultados mostram claramente o
enfraquecimento dos efeitos induzidos pela irradia??o quando o comprimento da trilha
? reduzido a poucos nan?metros. Desvios do comportamento observado para filmes
bulk come?am em uma espessura cr?tica ?1 t?o grande quanto ~40 nm para o volume
da protuber?ncia, devido ? redu??o dos efeitos de a??o cooperativa de material
excitado ao longo da trilha. Entretanto, ?1 ? bem menor para efeitos relacionados a
eventos pr?ximos ? superf?cie, como o tamanho cratera (?1~10 nm). C?lculos
anal?ticos pelo modelo do pulso de press?o foram utilizados para investigar aspectos
te?ricos da transfer?ncia de energia ?on-material no transporte e dissipa??o da energia
depositada. Os resultados obtidos a partir desses c?lculos corroboram com
observa??es experimentais. As modifica??es qu?micas foram investigadas atrav?s
das se??es de choque de quebra de liga??es, extra?das por espectroscopia de
fotoel?trons por raios x. As se??es de choque de danos para as liga??es carbonooxig?nio,
obtidas para irradia??es com ?ons de Bi de 2,2 GeV, s?o levemente
reduzidas para filmes mais finos, enquanto as se??es de choque para filmes irradiados
com pr?tons de 2 MeV n?o mostram diferen?as significativas at? a espessura mais
fina acess?vel por an?lise de XPS (?~5 nm). A partir desse conjunto de dados verificou-se
o enfraquecimento dos efeitos induzidos pela irradia??o em filmes polim?ricos sob
confinamento espacial em camadas com ? abaixo de um valor cr?tico ?1, sendo ?1
dependente do efeito sondado. N?o foram observadas diferen?as significativas do
efeito da espessura para diferentes substratos.
| Identifer | oai:union.ndltd.org:IBICT/oai:tede2.pucrs.br:tede/5905 |
| Date | 30 March 2015 |
| Creators | Thomaz, Raquel Silva |
| Contributors | Papal?o, Ricardo Meurer |
| Publisher | Pontif?cia Universidade Cat?lica do Rio Grande do Sul, Programa de P?s-Gradua??o em Engenharia e Tecnologia de Materiais, PUCRS, Brasil, Faculdade de Engenharia |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da PUC_RS, instname:Pontifícia Universidade Católica do Rio Grande do Sul, instacron:PUC_RS |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 4953914605093919665, 600, 600, 600, -655770572761439785, 4518971056484826825 |
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