Computer simulation of growth and photo-induced phenomena [Elektronische Ressource] / József Hegedüs

Joco

Sujets

• Physik

Informations

• Publié par: philipps-universitat_marburg
• Publié le: 01 janvier 2006
• Nombre de lectures: 8
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

DOCTORAL DISSERTATION




Computer simulation of
growth and photo-induced
phenomena



József Hegedüs

from Budapest, Hungary


Thesis advisors:

Prof. Sándor Kugler
Department of Theoretical Physics,
Budapest University of Technology and Economics



and


Prof. Peter Thomas
Fachbereich Physik und
Wissenschaftl. Zentrum für Materialwissenschaften
der Philipps-Universität Marburg




2006







































Vom Fachbereich Physik der Philipps-Universität
als Dissertation angenommen am 31.07.2006
Erstgutachter: Prof. Dr. Stephen R. Elliott (Cambridge, UK)
Zweitgutachter: Prof. Dr. Sergei Baranovski (Marburg, Germany)
Tag der mündlichen Prüfung: 22.08.2006
Table of Contents

1 Introduction...................................................................................................1
2 Kinetic Monte Carlo simulation of impurity induced growth instabilities...3
2.1 .................................................................................................. 3
2.1.1 Illustration of effects of immobile impurities in a one dimensional
model system ....................................................................................................... 5
2.1.2 Overview of literature.......................................................................... 8
2.2 Simulation Method ...................................................................................... 9
2.2.1 Kinetic Monte Carlo algorithm............................................................ 9
2.2.2 Relative probabilities of events.......................................................... 10
2.2.3 Deposition of crystal atoms and impurities to the surface................. 14
2.2.4 Boundary conditions 15
2.2.5 Implementation .................................................................................. 16
2.2.6 Data analysis and storage................................................................... 18
2.3 Discussion of results 19
2.3.1 Investigation of the parameter regime ............................................... 19
2.3.2 Step-pairing and space-time plots...................................................... 21
2.3.3 Systems with three steps.................................................................... 27
2.3.4 s with eight steps 29
2.4 Conclusion ................................................................................................. 31
2.5 Bibliography .............................................................................................. 32
3 Molecular dynamics simulation of preparation of amorphous
semiconductors ...........................................................................................................33
3.1 Introduction................................................................................................ 33
3.2 Molecular dynamics simulation................................................................. 34
3.2.1 Empirical interatomic potential to describe Selenium-Selenium
interaction .......................................................................................................... 35
3.2.2 Tight-binding models for Selenium................................................... 36
3.2.3 Tight-binding models for Silicon....................................................... 38
3.2.4 Development and testing the molecular dynamics program package
ATOMDEP ........................................................................................................ 38
3.3 Comparison of different preparation techniques of amorphous Selenium
using molecular dynamics simulation.................................................................... 38
3.3.1 Selenium, the model material of chalcogenide glasses...................... 39
3.3.2 Simulation details .............................................................................. 39
3.3.3 Bombarding energy dependence of amorphous structures................ 46
3.3.4 Growth versus rapid quenching ......................................................... 53
3.3.5 Conclusion ......................................................................................... 57
3.4 Growth of amorphous Selenium thin films: classical versus quantum
mechanical molecular dynamics simulation.......................................................... 58
3.4.1 Motivation.......................................................................................... 58
3.4.2 Simulation details 58
3.4.3 Applied potentials.............................................................................. 59
3.4.4 Analysis of amorphous structures...................................................... 60
3.4.5 Conclusion 67
3.5 Two different tight-binding models. Description of structures obtained by
them ...................................................................................................................68
3.5.1 Motivation 68
3.5.2 Simulation details .............................................................................. 68
3.5.3 Amorphous structures grown by different tight-binding models....... 70
3.5.4 Compatibility with the Wooten-Winer-Weaire model ...................... 75
3.5.5 Conclusion ......................................................................................... 76
3.6 Bibliography .............................................................................................. 77
4 Light-induced volume changes in chalcogenide glasses ............................79
4.1 Introduction................................................................................................ 79
4.2 Simulation method..................................................................................... 79
4.3 Sample preparation .................................................................................... 82
4.4 Light induced phenomena.......................................................................... 86
4.4.1 Electron excitation ............................................................................. 86
4.4.2 Hole creation...................................................................................... 89
4.5 Macroscopic models .................................................................................. 91
4.5.1 Ideal, reversible case (a-Se)............................................................... 91
4.5.2 Non-ideal, irreversible case (a-As Se ) ............................................. 93 2 3
4.6 Summary.................................................................................................... 95
4.7 Bibliography .............................................................................................. 96
Summary.....................................................................................................................97
Zusammenfassung (In German) ...............................................................................100
Összefoglalás (In Hungarian) ...................................................................................103
Acknowledgements...................................................................................................106
List of publications ...................................................................................................107
Curriculum vitae .......................................................................................................108























1 Introduction

Computers become more and more important in every aspect of our life. Their expo-
nentially growing power draws the attention of scientists to solve otherwise unsolv-
able problems using computer simulations. Computer experiments are just like real
experiments. In real experiments we need samples, equipments, measurements and
data analysis. Analogously, computer experiments need models, program codes,
simulations and data analysis. Using increasing amount of computer resources we
approach more and more the reality during our simulations. They explain scientific
phenomena and reduce risk of future experiments. They are important both to sci-
ence and to industry. Experts are needed to make use of the exploding growth of
computational power. Interest in computer simulations is now greater than ever.
The physical properties of solids are fundamentally determined by their
atomic structure. Atomic structure on the other hand is influenced by the preparation
conditions. Computer simulation of the preparation provides insight into how the
atomic structure of the prepared material is influenced during preparation. Simulation
of preparation of materials is therefore of high importance because it helps to opti-
mize their physical properties for applications. In Chapter 2 and Chapter 3 I explore
ways to investigate the preparation of crystalline