This work presents the synthesis of metal oxide (MO_x) nanowires by the VLS mechanism using aerosol catalyst nanoparticles. In the absence of a substrate, nanowires grow continuously and entirely floating in the gas phase. Because of their extremely high aspect ratio, the MO_x nanowires can entangle and form freestanding network materials, similar to diaphanous webs. Previous work with SiC nanowires resulted in growth rates up to 50 µm/s and an aspect ratio of 2200; in this case study, the reaction was rationalised through in-situ sampling of reaction products and catalyst aerosol, and thermodynamic calculations of the bulk ternary Si-C-Fe phase diagram.[1]

The intrinsic characteristics of the synthesis method (e.g., high-aspect-ratio nanowires and growth rates orders of magnitude higher than conventional CVD) are expected to be universal for the formation of any nanowire material and have been recently proven for Si[2] and SiC[1]. Hereby, the catalyst aerosol evolution and the synthesis parameter space for MO_x nanowire webs are explored with in-situ sampling and characterization techniques. We explore the synthesis parameters that control selectivity for catalysed VLS nanowire growth over other competing reactions, such as temperature profile, oxygen concentration and catalyst residence time.

References

[1] R. S. Schäufele, M. Vazquez-Pufleau and J. J. Vilatela, Mater. Horizons, 2020, 7, 2978–2984.

[2] I. Gómez-Palos, M. Vazquez-Pufleau, J. Valilla, Á. Ridruejo, D. Tourret and J. J. Vilatela, Nanoscale, 2022, 14, 18175–18183.