The vapor-liquid-solid (VLS) nanowire growth mechanism is ubiquitous in semiconductor nanowire synthesis. These one-dimensional nanostructures are important for applications such as solar cells, Li-ion batteries, and gas sensors. VLS synthesis is known to produce single-crystalline nanowires with diameters, lengths, dopant concentrations, and interfaces that can be tuned throughout the growth process. Theoretical predictions suggest that VLS growth is governed by steady-state kinetics, and that the crystal chemistry important for the reverse process may be different from that which governs nanowire growth. We have developed a technique to directly observe the reverse process of Au-catalyzed SnO2 VLS nanowire growth – namely the etching of SnO2 nanowires by the Au nanoparticles at their tip – using in situ heating in a transmission electron microscope (TEM). This process is the opposite of the growth mechanism, and has been dubbed SLV. By utilizing energy dispersive x-ray spectroscopy (EDS), we can track the Sn content of the Au catalyst particle as the nanowire dissolves at the solid-liquid interface, and evaporates at the liquid droplet surface. This method provides an experimental platform to explore the VLS nanowire growth mechanism, including measuring the saturation concentration of a reactant within a VLS catalyst droplet. This technique is further extended to combine SLV with VLS growth, to produce integrated metal oxide heterostructures.

Linking the forward and reverse vapor-liquid-solid mechanisms in metal oxide nanostructures

253rd National Meeting (2017)

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