Materials Research Lecture

Semiconductors can be rendered plasmonic by doping to create high concentrations of free carriers. Degenerately doped wide band gap metal oxides are commonly used as transparent conductive thin films in optoelectronic devices, and these same materials exhibit localized surface plasmon resonance (LSPR) when synthesized as discrete colloidal nanocrystals. Based on the dynamic responsive behavior of the infrared LSPR absorption of these new materials, we are developing a new class of smart windows that can dynamically control heat loads and daylighting in buildings. Advancing further applications of plasmonic oxide nanocrystals, relies on better understanding LSPR in prototypical materials like ITO and developing innovative approaches to control doping, shape, and size, including novel compositions. Many applications of interest will hinge, in part, on the ability to concentrate infrared light into nanoscale volumes and to enhance electronic and vibrational state transitions via associated field enhancement effects. We are engineering the selection of dopants and crystalline properties of our nanocrystals to tune their LSPR modes, with a conceptual underpinning of density functional theory and electromagnetic simulations. By measuring LSPR spectra of individual nanocrystals using tip-enhanced synchrotron FTIR spectroscopy we characterize the intrinsic dielectric properties of these new materials. As such we can predict strong near field of infrared light is possible using plasmonic metal oxide nanocrystals. Finally, the first results demonstrating strong coupling in the near field will be presented.