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Cherie R. Kagan Research Group

Electrical and Systems Engineering | Chemistry | Materials Science and Engineering


Group Photo 2010

Our Research

Our research explores the chemical and physical properties of molecular, supramolecular, and nanostructured materials and assemblies and their potential applications in electronic, optoelectronic, and sensing devices. Molecule-surface and molecule-molecule interactions drive molecular organization. We exploit these chemical interactions to construct functional supramolecular and nanocrystal assemblies. Electrical measurements, optical spectroscopies, electrochemistry, and scanning probe and electron microscopies are used to probe the structure-function relationships of molecular assemblies and their interfaces with zero-, one-, and two-dimensional inorganic surfaces. These experiments provide a basis for understanding intermolecular, intramolecular, and interfacial (organic-inorganic) charge and excitonic transport and interactions. These insights are used to guide the rational design of molecular and nanostructured devices ranging from transistors to solar cells to photonics to chemical and biological sensors.

Our labs are equipped for chemical synthesis and assembly, cw and ultrafast spectroscopies with high spatial resolution, electrical measurements, and the complete fabrication of molecular and nanostructured materials in devices. Micron and nanoscale device fabrication is carried out in Pennís Wolf Nanofabrication Facility and structural characterization is performed in Pennís Regional Nanotechnology Facility.

Our group is interdisciplinary with students from the Departments of Electrical and Systems Engineering, Materials Science and Engineering, and Chemistry. We have collaborations with groups in the Schools of Engineering and Applied Sciences, Arts and Sciences, and Medicine and through Pennís Laboratory for the Research on the Structure of Matter and Pennís Energy Research Group.

Group Announcements

Congratulations to Dr. Fafarman!

Dr. Aaron Fafarman, who for the past few years has been a post-doc and an important part of our lab, will begin at Drexel this September as a Professor of Chemical and Biomolecular Engineering. Congratulations!

1st Place NASA Intern

Congratulations to Devika Mehta for taking 1st plact at the NASA Intern Poster Expo in Materials Engineering!

Rachleff Scholar Honorable Mention

Congratulations to Emily Gurniak for taking an honorable mention for her presentation and poster at the 2013 Rachleff Symposium Competition!

Research Highlights

High-Performance Lead Chalcogenide Devices through Post-synthesis, Colloidal Atomic Layer Deposition

We report a simple, solution-based, post-synthetic colloidal, atomic layer deposition (PS-cALD) process to engineer stepwise the surface stoichiometry and therefore the electronic properties of lead chalcogenide nanocrystal (NC) thin films integrated in devices. We found that unlike chalcogen-enriched NC surfaces that are structurally, optically and electronically unstable, lead chloride treatment creates a well-passivated shell that stabilizes the NCs. Using PS-cALD of lead chalcogenide NC thin films we demonstrate high electron field-effect mobilities of ~4.5 cm2/Vs.

Air-Stable, Solution Processable Ag NC Materials

We describe a room-temperature, chemical process to transform silver nanocrystal solids, deposited from colloidal solutions, into highly conductive, corrosion-resistant, optical and electronic materials with nanometer-scale architectures. We show ammonium thiocyanate uniquely form low-resistivity, optically smooth thin films that can be patterned by imprint lithography to form conductive electrodes and plasmonic mesostructures with programmable resonances.

Solution-Processed Phase-Change VO2 Metamaterials

We demonstrate thermally switchable VO2 metamaterials by combining nanoimprinting and solution-based deposition of colloidal nanocrystals. We tuned the phase change temperature by W-doping the NCs and fabricated differentially-doped, multilayered materials to tailor the optical response in the near-IR and IR from that of a strong light absorber to that of a Drude like reflector with a change in temperature.

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Copyright © 2011 Kagan Research Group, University of Pennsylvania
Electrical & Systems Engineering, Moore Building
200 South 33rd Street, Philadelphia, PA 19104