In Situ Growth of GaP Nanowires with Alternative Seed Materials

The growth of III-V nanowires has attracted significant attention due to their superior electrical and optical properties, which are crucial for advanced optoelectronic devices such as lasers and photonic circuits. Since the 1960s, Au has beenextensively used as a catalyst for III-V nanowire growth, with substantial research conducted through both ex situ and in situ techniques. However, Au introduces deep-level impurities in Si-based semiconductors, posing challenges for nanowire-based optoelectronic applications. This limitation underscores the importance of exploring alternative seed materials. To date, studies on alternative catalysts, such as Cu, Ni, and Pd, remain limited, and the underlyingmechanisms governing their catalytic behavior in nanowire growth are not yet well understood.In this thesis, the growth of GaP nanowires was observed inside an environmental transmission electron microscope using these alternative seed materials. This study emphasizes the critical influence of seed particles and growthparameters on nanowire nucleation, growth dynamics, and morphological evolution.Initially, I observed the early stages of GaP growth, characterized by phase transformations between the deposited Cu and Ni nanoparticles and the introduced precursors, followed by GaP nucleation on the seed particles. Subsequentinvestigations into nanowire growth dynamics revealed a broader range of seed particle phases than those observed during nucleation. The distinct growth behavior demonstrates a hierarchical effect, wherein growth parameters dictatethe crystal phases of seed particles, which further influence the nanowire growth dynamics. Additionally, by adjusting the precursor flow, a transition between the vapor-solid-solid and vapor-liquid-solid growth regimes was observed,allowing for controlled tuning of the nanowire diameter.The findings of this thesis provide fundamental insights into the mechanisms governing nanowire growth with alternative seed materials, offering a deeper understanding of the relationship between growth parameters, seed particlebehavior, and nanowire growth dynamics. By clarifying these processes, this study contributes to the broader effort of optimizing nanowire synthesis for improved control over their structural and functional properties. Ultimately, theseinsights open new avenues for the fabrication of high-performance III-V semiconductor nanowires, facilitating their integration into next-generation electronic and photonic devices.