Influence of Seed Particle Material, Preparation, and Dynamics on Nanowire Growth

Abstract: Semiconducting nanowires have attracted scientific attention for more than 20 years due to their potential applications in electronic devices, as sensors, and in solid state lighting. These applications require high quality nanowires to begin with. Achieving such good control over the growth of nanowires is not trivial and requires profound understanding of the underlying processes.
In this thesis, nanowires of different materials and combinations thereof have been grown with the help of seed particles by metal-organic vapor phase epitaxy (MOVPE). The focus of the investigations lies on the influence of several seed particle properties on nanowire growth.
First, we compared six particle preparation and deposition methods for the most common seed particle material – gold - and their influence on the growth of GaAs nanowires. We observed only small differences, mainly in incubation times, which did not have a significant effect on the nanowire length after some growth time, though. The optical properties, however, varied between nanowires seeded by different particle types.
Further, copper as seed particle material for growth of InP nanowires and InP-InAs heterostructures was investigated. The aim was to get a deeper understanding of which properties or combination of properties determine a “good” seed particle material. InP nanowire growth from Cu particles differs a lot from nanowire growth from Au seed particles in terms of temperature range and precursor molar fractions. Furthermore, growth from two types of particles – Cu-rich and In-rich – occurs simultaneously at low V/III ratios. The investigations of InP-InAs heterostructures showed that it is indeed possible to grow straight heterostructures, but we observed unusual layer formation of the InAs segments.
Finally, we used the possibility of in situ TEM to investigate nanowire growth at the IBM T.J. Watson Research Center. We combined group IV and group III/V materials and investigated the particle dynamics that may lead to kinking. In addition, we investigated the instantaneous kinetics of GaP growth.