Near-field Vibrational Imaging of Doping and Thermal Effects in Polymer Thin Films

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With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program in the Division of Chemistry and the Established Program to Stimulate Competitive Research (EPSCoR), Terefe Habteyes of the University of New Mexico will investigate chemical phase separation, charge localization, and localized thermal effects in polymer thin films to map chemical heterogeneity with nanometer spatial resolution and to develop a better understanding of localized electron transfer processes. Scattering-type scanning near-field optical microscopy (s-SNOM) and localized Fourier transform infrared (nano-FTIR) spectroscopy allow for the direct visualization of chemical species in organic films with ~10 nm spatial resolution. Improving the understanding of how carriers are transported across an interface has the potential to advance fabrication methods of various electronic films, photovoltaics, and displays. Research performed by the Habteyes research team will be enhanced through collaborations with federal government laboratories. Dr. Habteyes and his group will also engage high school teachers and students through summer outreach activities. This project relies on the use of a sharp probe that serves as a nanoantenna for nano-FTIR spectroscopy and s-SNOM chemical imaging measurements. Nano-FTIR spectroscopy identifies chemical species in organic material blends, while s-SNOM imaging maps the chemical species in two-dimensions. The research team will evaluate molecular doping and charge localization in organic semiconductors (OSCs), hot electron transfer to OSC and molecular dopants, and temperature-dependent intermolecular interaction in polymer blends. The direct observation of charge states and chemical complexes with nanoscale spatial resolution will inform how material fabrication is influenced as a function of solution processing and organic thin film post-processing steps. The fundamental understanding obtained from this research has the potential to advance the application of polymeric materials for different technologies such as photovoltaics, field effect transistors, photodetectors, thermoelectric and other emerging applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.