There are many applications (e.g., large area electronics, solar and thermal energy harvesters, artificial skins, etc.) where the constituent materials and devices require controlled nanoscale compositional heterogeneity and must also be produced at very large scales. Purely top-down fabrication techniques are unlikely to succeed in both regards. The bottom-up vapor-liquid-solid (VLS) mechanism – whereby a liquid eutectic “catalyst” droplet collects precursor molecules from the vapor and directs crystallization of a semiconductor nanowire – promises the requisite programming of composition at the nanoscale while being amenable to high throughput manufacturing. However, in many cases, it remains challenging to precisely control nanowire structure and function. To this end, we combine <i>in situ</i> infrared spectroscopy and electron microscopy to probe the heterointerfacial chemical processes that govern nanowire growth. Our studies reveal the presence and dramatic influence of various adsorbed species. We find, for example, that changes to hydrogen atom coverage on the nanowire sidewall impact catalyst phase, atomic transport to/from the catalyst, dopant profile, heterostructure formation, and nanowire growth direction. These insights not only provide guidelines for advancing synthetic design, but also enable a previously unattainable level of nanoscale fidelity and functionality.

Surface chemical choreography of vapor-liquid-solid semiconductor nanowire synthesis

255th National Meeting (2018)

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