CAREER: Linking the Forward and Reverse Vapor-Liquid-Solid Mechanisms to Synthesize Ordered Integrated Metal Oxide Nanostructures

University Of Kentucky Research Foundation, Lexington KY

Investigators

Abstract

Non-technical Description. We live in a society with reliance on materials, in particular those that enable the generation or storage of energy, for which the efficiencies that are required are ever growing. The function of such materials increasingly relies on creating highly-efficient and closely-spaced crystal interfaces including, for example, large area p-n junction arrays for solar devices. This project to understand and exploit the solid-iquid-vapor mechanism should provide a new approach to engineer nanostructured composite materials with highly efficient single-crystalline components, thus having a significant positive impact on the directed design of metal oxide materials, and on the society that relies on them. Based on this research and the infrastructure developed to support it, are a series of educational and outreach activities, designed to increase participation in research experiences by University of Kentucky undergraduates. Technical Description. Though the vapor-liquid-solid (VLS) mechanism has been extensively studied in its role in metal-catalyzed nanowire growth, the reverse of this process - the solid-liquid-vapor (SLV) mechanism - is not well understood, yet it could well provide the key to understanding and utilizing VLS-grown wires. Thus, there is a critical need to determine the key factors governing the SLV mechanism and its fundamental relationship to VLS growth. The objective in this project is to determine the key parameters that govern the SLV mechanism in metal oxides, and the relationship linking SLV to the VLS mechanism. The central hypothesis is that if a single metal nanodroplet can be used in the VLS growth of a nanowire, it will also catalyze the SLV dissolution of the same material, with crystallographic specificity equivalent to that of the original growth. The rationale is that a greater understanding of SLV and its relation to VLS could provide a route to highly-specified porous materials, as well as a method of precise placement for high-quality nanowires synthesized with a "bottom-up" approach. The successful completion of these studies is expected to have a significant positive impact on the directed design of functional metal oxide materials since it will enable the production of structures, compositions, and arrangements of interfaces with a high degree of control and complexity. This research is significant because combining SLV with VLS will for the first time enable control of the nanowire-template interface, essentially "synthesizing" interfaces with specific chemistry, crystallography, and spacing.