Cherie R. Kagan
Department of Electrical and Systems Engineering, Department of Materials Science and Engineering and Department of Chemistry
University of Pennsylvania
Seminar: Electronic and Optical Devices Constructed from Colloidal Nanocrystals
Abstract: Semiconductor and noble metal nanocrystals are known for their size- and shape-dependent photoluminescence 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. Nanocrystals have inorganic cores and organic or inorganic ligand shells. 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 and 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. 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 distinct chemical, mechanical, and thermal properties of metal NCs to realize ultrathin film absorbers and large-area, 2D and 3D chiral, polarizing metamaterials.
About the Speaker: Cherie R Kagan is the Stephen J Angello Professor of Electrical and Systems Engineering at the University of Pennsylvania. She is Penn Engineering’s Associate Dean for Research, the 2021 President of the Materials Research Society, and an Associate Editor of ACS Nano. Kagan is also the Director of the National Science Foundation Engineering Research Center for the Internet of Things for Precision Agriculture. Kagan’s research is focused on studying the chemical and physical properties of nanostructured materials and in integrating materials with optical, electrical, magnetic, mechanical, and thermal properties in (multi-)functional devices with applications in electronics, photonics, and sensing.
Host: Avik Ghosh, professor of electrical and computer engineering and professor of physics (by courtesy)