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Theses Year : 2012

Charged defects in Silicon Nanoclusters

Lacunes chargées, étude dans des nano-agrégats de silicium

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Abstract

In this work we have studied Si clusters with point defects in various charged states. Point defects in semiconductors affects the electronic structure of the material introducing new energy levels and consequently new modes of transport.Detailed study of the point defects have been undertaken in various approaches. The most common practice is to usesuper-cell calculations under the framework of Density Functional Theory with Periodic Boundary Conditions (PBC). Inthis formalism there are a lot of factors like defect-defect interactions, image charge interactions, that are to be correctedfor to achieve the " artefact-free" results. In this study we have used Free Boundary Conditions with nano-clusters of Sipassivated with Hydrogen at the surface. Previous works have undertaken in detail the geometrical effects in the nanoclusters. But a complete picture of the electrostatics and its effect on the energy states demand a complete study. Hence inour calculations we take another approach, devoid of the correction factors for cases with PBC, and produce an alternativeway to calculate the formation energy of the defects. We have described the formation and stability of the defects invarious charged states and provided with a detailed analysis of the properties pertaining to the nano-scale size. Finallymigration parameters are provided with respect to the charge states of the defects. Our results are also compared with thePBC calculations with critical discussions.
Ce travail aborde le sujet des d efauts charg es dans le silicium. Jusqu' a pr esent, les d efauts charg es ont principalement et e etudi es en conditions p eriodiques (PBC). En e et, l'approche PBC est parfaite pour simuler unsolide in ni. Mais, comme je le montre dans ce chapitre, elle apporte aussi des artefacts. En particulier dans le traitement de l' electrostatique, o u des traitements math ematiques important doivent ^etre utilis es pour supprimer les interactions non d esir ees entre r epliques. Notre approche vise a simuler correctement un d efaut charg e, tout en conservant de bonne propri et es pourle mat eriau massif. Elle consiste a simuler le d efaut dans un nano-agr egat. Le traitement de l' electrostatique est correct dans un nano-agr egat et les r esultats obtenus peuvent ^etre extrapol es au mat eriau massif, comme il est montr e dans ce chapitre. Les perspectives de cette m ethode sont aussi abord ees ici.
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Dates and versions

tel-00744666 , version 1 (23-10-2012)

Identifiers

  • HAL Id : tel-00744666 , version 1

Cite

Arpan Deb. Lacunes chargées, étude dans des nano-agrégats de silicium. Autre [cond-mat.other]. Université de Grenoble, 2012. Français. ⟨NNT : 2012GRENY027⟩. ⟨tel-00744666⟩
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