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Point defect and surface properties of In2O3 and SnO2: A comparative study by first-principles methods

Agoston, Peter (2011):
Point defect and surface properties of In2O3 and SnO2: A comparative study by first-principles methods.
Darmstadt, TU Darmstadt,
[Ph.D. Thesis]

Abstract

The first part of the dissertation deals with the thermodynamic stability of point defects in In2O3 and SnO2. This is done by first surveying possible defect geometries using density functional theory (DFT) total energy calculations in order to identify relevant structures. The formation energies of selected defects are then further refined by estimating their formation entropies as well as by using more sophisticated DFT approximations like hybrid-functionals. The second part deals with the kinetic properties of point defects. The migration barriers of a range of defects is calculated in various charge states in order to estimate the diffusion constants and equilibration temperatures. The third part finally turns to the surface properties of In2O3 and SnO2. First, the controversially discussed thermodynamic ground state properties of SnO2 surfaces are resolved and complemented. Then a detailed survey on the stability and structure of surfaces is conducted for In2O3 surfaces. The influence of water, strain, dopants and band bending are discussed and linked to experimental observations. Finally, the properties of bulk defects and surfaces are compared for the two materials.

Item Type: Ph.D. Thesis
Erschienen: 2011
Creators: Agoston, Peter
Title: Point defect and surface properties of In2O3 and SnO2: A comparative study by first-principles methods
Language: English
Abstract:

The first part of the dissertation deals with the thermodynamic stability of point defects in In2O3 and SnO2. This is done by first surveying possible defect geometries using density functional theory (DFT) total energy calculations in order to identify relevant structures. The formation energies of selected defects are then further refined by estimating their formation entropies as well as by using more sophisticated DFT approximations like hybrid-functionals. The second part deals with the kinetic properties of point defects. The migration barriers of a range of defects is calculated in various charge states in order to estimate the diffusion constants and equilibration temperatures. The third part finally turns to the surface properties of In2O3 and SnO2. First, the controversially discussed thermodynamic ground state properties of SnO2 surfaces are resolved and complemented. Then a detailed survey on the stability and structure of surfaces is conducted for In2O3 surfaces. The influence of water, strain, dopants and band bending are discussed and linked to experimental observations. Finally, the properties of bulk defects and surfaces are compared for the two materials.
Place of Publication: Darmstadt
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 04 Nov 2011 12:23
Official URL: urn:nbn:de:tuda-tuprints-27811
License: Creative Commons: Attribution-Noncommercial-No Derivative Works 3.0
Referees: Albe, Prof. Karsten ; von Seggern, Prof. Heinz
Refereed / Verteidigung / mdl. Prüfung: 6 July 2011
Alternative Abstract:
Alternative abstract Language

Der erste Teil dieser Studie beschäftigt sich mit der thermodynamischen Stabilität von Punktdefekten in In2O3 und SnO2. Hierzu werden eine Reihe von Gesamtenergierechnungen auf Grundlage der Dichtefunktionaltheorie (DFT) durchgeführt und relevante Defektstrukturen identifiziert. Die Bildungsenergien relevanter Defekte werden im Folgenden weiter verfeinert indem die Defektbildungsentropie berechnet wird bzw. verbesserte Näherungen der DFT wie z.B. Hybridfunktionale eingesetzt werden. Der zweite Teil der Studie beschreibt die kinetischen Eigenschaften der Punktdefekte. Die Migrationsenergien einer Reihe relevanter Defekte werden für verschiedene Ladungszustände berechnet. Mit deren Hilfe werden die Diffusionskonstanten sowie Equilibrationstemperaturen der Materialien abgeschätzt. Im dritten Teil werden schliesslich die Oberflächeneigenschaften von In2O3 und SnO2 untersucht. Zunächst werden die kontrovers diskutierten Grundzustandseigenschaften von SnO2 Oberflächen aufgeklärt und ergänzt. Im Anschluss wird die Stabilität und Struktur von In2O3 Oberflächen im Detail beschrieben. Der Einfluss von Wasser, mechanische Dehnung sowie Dotierung und Bandverbiegung wird diskutiert und mit experimentellen Beobachtungen verknüpft. Schliesslich werden die Eigenschaften von Volumendefekten und Oberflächen der zwei Materialen verglichen.

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