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

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

Growth Mechanism of Self-Catalyzed Group III−V Nanowires

Group III-V nanowires offer the exciting possibility of epitaxial growth on a wide variety of substrates, most importantly silicon. To ensure compatibility with Si technology, catalyst-free growth schemes are of particular relevance, to avoid impurities from the catalysts. While this type of growth is well-documented and some aspects are described, no detailed understanding of the nucleation and the growth mechanism has been developed. By combining a series of growth experiments using metal-organic vapor phase epitaxy, as well as detailed in situ surface imaging and spectroscopy, we gain deeper insight into nucleation and growth of self-seeded III-V nanowires. By this mechanism most work available in literature concerning this field can be described

Epitaxial InP nanowire growth from Cu seed particles

Cu-seeded epitaxial growth of vertically aligned InP nanowires is reported for the first time. The nanowires were grown at temperatures between 290 and 420 degrees C by metal-organic vapor phase epitaxy (MOVPE) from particles formed from Cu thin films. In the temperature range of 340-370 degrees C high yields of vertically aligned nanowires could be achieved. The nanowire crystal structure and the particle composition were investigated by TEM and XEDS. The nanowires showed a zinc blende structure and a post-growth particle composition of 64 at% Cu and 36 at% In. (C) 2010 Elsevier B.V. All rights reserved

The use of gold for fabrication of nanowire structures

A common application of nanometer-sized gold particles is as seed particles for growth of semiconductor nanowires, which are believed to act as highly promising building blocks in future electronic devices. In a majority of the reports of successful nanowire growth, gold has been the seed particle material of choice. In this review article we identify the different types of gold particles used to initiate nanowire growth, namely gold particles made from thin films, gold particles defined by lithographic methods, colloidal gold particles and aerosol-generated gold particles. The production and deposition methods are described and the advantages and disadvantages of the particle types are discussed. In addition we discuss different properties that seem to make gold the most universal material for nanowire seed particles

Cu particle seeded InP InAs axial nanowire heterostructures

We demonstrate the epitaxial growth of alternating InP-InAs nanowire heterostructures using Cu seed particles in MOVPE. We observe extraordinary early stages in the formation of InAs segments, e.g. three-dimensional nucleation instead of step-flow growth. Furthermore, InAs segments of thin nanowires exhibit extended 4H crystal structure

Simultaneous growth mechanisms for Cu-seeded InP nanowires

We report on epitaxial growth of InP nanowires (NWs) from Cu seed particles by metal-organic vapor phase epitaxy (MOVPE). Vertically-aligned straight nanowires can be achieved in a limited temperature range between 340 A degrees C and 370 A degrees C as reported earlier. In this paper we present the effect of the V/III ratio on nanowire morphology, growth rate, and particle configuration at a growth temperature of 350 A degrees C. Two regimes can be observed in the investigated range of molar fractions. At high V/III ratios nanowires grow from a solid Cu2In particle. At low V/III ratios, nanowire growth from two particle types occurs simultaneously: Growth from solid Cu2In particles, and significantly faster growth from In-rich particles. We discuss a possible growth mechanism relying on a dynamic interplay between vapor-liquid-solid (VLS) and vapor-solid-solid (VSS) growth. Our results bring us one step closer to the replacement of Au as seed particle material as well as towards a deeper understanding of particle-assisted nanowire growth

A comparative study of the effect of gold seed particle preparation method on nanowire growth

Highly controlled particle-assisted growth of semiconductor nanowires has been performed for many years, and a number of novel nanowire-based devices have been demonstrated. Full control of the epitaxial growth is required to optimize the performance of devices, and gold seed particles are known to provide the most controlled growth. Successful nanowire growth from gold particles generated and deposited by various different methods has been reported, but no investigation has yet been performed to compare the effects of gold particle generation and deposition methods on nanowire growth. In this article we present a direct comparative study of the effect of the gold particle creation and deposition methods on nanowire growth characteristics and nanowire crystal structure, and investigate the limitations of the different generation and deposition methods used