We study the interaction between dislocations and smooth elastic strains in thin film growth. In the first part of the thesis, a continuum model is introduced which, for the first time, includes nucleation, interaction, and dynamics of dislocations in an external stress field in two spatial dimensions. The model implicitly includes the presence of boundaries and their coupling to the elastic strains in the system. In particular, it naturally gives rise to the two well-known strain relaxation modes in thin films: the Asaro-Tiller-Grinfeld (ATG) morphological instability, leading to a grooved morphology of the film-vapor interface, and the nucleation of misfit dislocations for films thicker than the Matthews-Blakeslee critical thickness. The novelty of the model resides in the fact that both of these mechanisms are explicitly incorporated within a unified approach. Therefore, this is a generic model for dislocations in strained heterogeneous systems. / In the second part of the thesis, this model is applied to thin film growth with dislocations. It is shown that the film undergoes an ATG instability. However, the accumulation of dislocations at the film-substrate interface leads to an effectively screened stress in the film, and hence buckling occurs at longer wavelengths. In particular, it is shown that the film remains planar for sufficiently effective screening. Furthermore, the effect of dislocations depends very strongly on their equilibrium density and mobility. It is also shown that, in the late-time regime, dislocations interact strongly with the stress enhancement at the bottom of the grooves. In particular, this leads to a buildup of localized dislocations around the stress concentrations, in addition to dislocations at the film-substrate interface. This in turn leads to very complicated film morphologies, in qualitative agreement with experiments. / In the last part of the thesis, the dynamics of a single groove is studied in a strip geometry, both with and without dislocations. In the absence of dislocations, it is argued theoretically and shown numerically, that the groove attains a steady-state. A theoretical argument is given for the shape of the groove, and good agreement with numerics is found. Upon including noise in the dynamics, a morphological transition from straight to oscillatory propagation is found. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.37897 |
| Date | January 2001 |
| Creators | Haataja, Mikko. |
| Contributors | Grant, Martin (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001846214, proquestno: NQ75639, Theses scanned by UMI/ProQuest. |
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