Opening the Black Box of III-V Nanowire Growth

Group III-V semiconductor nanowires are a material platform with potential applications in electronics,
photovoltaics and optoelectronic devices. One of the central challenges in the growth of III-V semiconductor
nanowires is to understand the dynamic processes that occur during crystallization. However, the growth of these
materials is commonly performed in closed systems. There the details of the growth dynamics are hidden from us,
resulting in these systems being described as black boxes. Therefore, nanowire growth studies in the past generally
have relied on a combination of theoretical modelling coupled with post growth analysis of the as-grown nanowires.
This thesis presents a different approach. Here the black box of nanowire growth is opened by performing the growth
of Au-seeded III-V semiconductor nanowires in an environmental transmission electron microscope. This enables us
to study nanowire growth in situ, effectively coupling the growth with real-time observations at atomic resolution.
This gives information about the fundamental interplay between vapour phase precursors, liquid seed nanoparticle
and solid nanowire during growth.
The ability to study growth in real time is used in this thesis to describe how the lateral dimensions of GaAs nanowires
affect the growth dynamics. This is achieved by acquiring high frame rate videos of the layer-by-layer growth process
and correlating the changes in dynamics to nanowire diameter. This is followed by a detailed characterization of
GaSb nanowires focused the aspects of morphology and growth dynamics, where I first discuss the impact of growth
conditions on the seed nanoparticle composition and morphology. Thereafter, I present how these conditions affect
the growing nanowire morphology and growth dynamics. Lastly, I showcase the formation of GaSb/GaAs axial
nanowire heterostructures. In addition to examining the growth parameters required for successful heterostructure
formation a detailed description of the growth dynamics during heterojunction formation is provided.
The findings presented in this thesis could be used to improve the modelling and growth of III-V nanowires using
conventional growth systems, to further our goal of controlling and more importantly understanding the growth of
these materials at the atomic scale.