Calculation of the 2D nucleation barrier

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Table of contents

Thesis overview
List of figures
List of tables
1 Vapor-liquid-solid growth of III-V nanowires
1.1 What are nanowires?
1.2 The vapor-liquid-solid mechanism of nanowire growth
1.2.1 Growth directions
1.2.2 Nanowire growth dynamics
1.3 Understanding NW growth with nucleation theory
1.3.1 Calculation of the 2D nucleation barrier
1.3.2 The classical nucleation rate
1.3.3 Polytypism in III-V nanowires
1.4 Self-catalyzed GaAs NWs: a model system
1.4.1 Crystal structure
1.5 Heterostructure formation in nanowires: advantages and challenges
1.5.1 The reservoir effect
2 Experimental methods
2.1 Molecular beam epitaxy
2.1.1 Effusion cells and flux measurements
2.1.2 RHEED
2.1.3 Absolute calibration of the vapor fluxes
2.2 Electron microscopy characterization
2.2.1 Scanning electron microscopy
2.2.2 Transmission electron microscopy
2.2.3 Quantification of composition using medium and high-resolution
HAADF contrast in scanning transmission microscopy
3 Study of correlations in the stacking sequence of a NW
3.1 Introduction
3.2 NW synthesis and data collection
3.3 Probabilistic analysis of the stacking sequence: conditional probabilities .
3.4 Distribution of cubic and hexagonal segments
3.5 The pair correlation function
3.6 Including correlations in the classical nucleation theory
3.6.1 Standard choice
3.6.2 ANNNI for the nucleus interface energy
3.6.3 Extending the ANNNI model to the step energy
3.7 Conclusions
4 Development of self-catalyzed Ga(As,P) axial heterostructures
4.1 Introduction
4.2 Growth of pure, self-catalyzed GaP nanowires
4.3 Growth of GaAs (GaP) insertions in GaP (GaAs)
4.4 Behavior of As and P fluxes
4.5 Morphology of the growth front
4.6 Conclusions
5 (Al,Ga)As axial heterostructures
5.1 (Al,Ga)As insertions in self-catalyzed GaAs NWs
5.2 Experimental details
5.3 Abruptness of interfaces
5.3.1 Estimation of Al fraction in the liquid
5.3.2 The effect of As flux and Al diffusion
5.3.3 Improving interface abruptness with droplet pre-filling
5.4 Modeling the interface composition
5.4.1 Liquid-solid equilibrium of the Al-Ga-As alloy
5.4.2 Predicting the composition profile
5.4.3 An analytical solution for the interface profile
5.5 Conclusions
6 On thin nanowires and the ultimate control of nucleation events
6.1 Nucleation statistics in time
6.1.1 Growth rate diagram of self-catalyzed GaAs nanowires
6.1.2 Depleting the droplet: growth versus evaporation
6.1.3 Difficulties of the steady-state approach
6.1.4 Pulsing the As supply
6.1.5 First experimental demonstrations
6.1.6 Conclusions
6.2 Growth of thin NWs
General conclusions and perspectives
References