ABSTRACT

Semiconductor and plasmonic nanocrystals are known for their size and shape dependent photo-luminescence and localized surface plasmon resonances, respectively. In this talk, I will describe the use of semiconductor and plasmonic nanocrystals as building blocks of mesoscale materials for semiconductor electronics and optoelectronics and plasmonic optical metamaterials. Chemical exchange of the long ligands used in nanocrystal synthesis with more compact ligand chemistries brings neighboring nanocrystals into proximity and increases interparticle coupling. In semiconductor nanocrystal solids, we show strong electronic coupling in combination with doping allows us to control the carrier type and concentration to design high mobility n- and p-type materials. I will give examples where n- and p-type nanocrystal solids are used to construct field-effect transistors and integrated circuits and solar photovoltaics. In metal nanocrystals, ligand-controlled coupling allows us to tailor a dielectric-to-metal phase transition seen by a 1010 range in DC conductivity and a dielectric permittivity ranging from everywhere positive to everywhere negative across the whole range of optical frequencies. We realize a "diluted metal" with optical properties not found in the bulk metal analog, presenting a new axis in plasmonic materials design and the realization of optical properties akin to next-generation metamaterials. We harness the properties of metal nanocrystals by using nanoimprint lithography to print large-area metamaterials on glass and plastics with widely tailorable optical properties that are used to realize near-infrared optical devices.

ABOUT THE SPEAKER

Cherie R. Kagan is the Stephen J. Angello Professor of Electrical and Systems Engineering, Professor of Materials Science and Engineering, and Professor of Chemistry at the University of Pennsylvania. Kagan is also an Associate Editor of ACS Nano. She graduated from the University of Pennsylvania in 1991 with a BSE in Materials Science and Engineering and a BA Mathematics and earned her PhD in Materials Science and Engineering from the Massachusetts Institute of Technology in 1996. In 1996, she went to Bell Labs as a postdoctoral fellow and in 1998, she joined IBM’s T. J. Watson Research Center, where she most recently managed the “Molecular Assemblies and Devices Group.” In 2007, she joined the faculty of the University of Pennsylvania. The Kagan group’s research is focused on studying the chemical and physical properties of nanostructured materials and in integrating these materials in electronic, optoelectronic, and optical devices. The group combines the flexibility of chemistry and bottom-up assembly with top-down fabrication techniques to design novel materials and devices and explores the structure and function of these materials and their devices.