Ultrafast Nonlinear Microscopy in Nanowires and Nanowire Networks

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In this project, funded by the Chemical Structure Dynamics and Mechanisms Program of the Chemistry Division, Prof. John M. Papanikolas of the University of North Carolina at Chapel Hill will combine pump-probe methodologies with nonlinear microscopy to investigate the charge carrier dynamics in one-dimensional nanostructures and networks on ultrafast time scales. The project will develop a new microscopy technique that will excite a nanostructure in one spatial location and probe the dynamics in another, on time scales ranging from femtoseconds to nanoseconds. Professor Papanikolas and his students will use this spatially-separated pump-probe microscope to visualize charge carrier migration through individual nanorods and networks. The project will focus primarily on nanowires with radial (i.e. core-shell) and axial heterojunctions with the goal of following carriers as the move through the structure, from one material to another.This project will investigate how size and shape influence the flow of charge carriers (electrons and holes) through both individual nanostructures and collections of interconnected nanostructures. This issue is fundamentally important and critical to understanding many problems in nanoscience and nanotechnology. Variation in behavior from structure-to-structure, and even between different spatial locations within the same structure, is a hallmark of complexity and its presence poses a major challenge to those wishing to use nanoscale materials in a device applications. The project will also promote teaching, training, and learning in the context of a research program. Graduate, undergraduate and high school students will participate in this research. They will develop the technologically sophisticated instrumentation, apply those methods to the study of single nanostructures, and take part in the communication of their results at national meetings.