Cherie R Kagan Research Group

Electrical and Systems Engineering - Chemistry - Materials Science and Engineering

Group Photo 2014


The Kagan Group explores the chemical and physical properties of nanostructured and organic materials and integrates these materials in electronic, optoelectronic, optical, thermoelectric and bioelectronic devices. We combine the flexibility of chemistry and bottom-up assembly with top-down fabrication techniques to design novel materials and devices. We explore the structure and function of these materials and devices using spatially- and temporally-resolved optical spectroscopies, AC and DC electrical techniques, electrochemistry, scanning probe and electron microscopies and analytical measurements.

Research Highlights

Increased Carrier Mobility and Lifetime in CdSe Quantum Dot Thin Films through Surface Trap Passivation and Doping

We investigate the effect of introducing indium in CdSe QD thin films on the dark mobility and the photogenerated carrier mobility and lifetime using field-effect transistor (FET) and time-resolved microwave conductivity (TRMC) measurements. As the amount of indium increases, the FET and TRMC mobilities and the TRMC lifetime increase. The increase in mobility and lifetime is consistent with increased indium passivating midgap and band-tail trap states and doping the films, shifting the Fermi energy closer to and into the conduction band.

Charge transport in strongly coupled quantum dot solids

Kagan and Murray review the chemical and physical origins of high mobility charge transport in quantum dot (QD) solids that is being exploited in devices. They also present future prospects for QD materials and device design.

Flexible, High-Speed CdSe Nanocrystal Integrated Circuits

We report large area, flexible, photopatterned integrated circuits based on CdSe nanocrystal semiconductors. Our results show high performance devices with transistor mobilities exceeding 10 cm2/Vs, amplifiers with ~7 kHz bandwidth, and oscillators with sub-10 Ás stage delays as well as NAND and NOR logic gates.

Substitutional doping in nanocrystal superlattices

In collaboration with the Murray group, we report substiutional doping of gold nanocrystals in superlattices of cadmium selenide and lead selenide quantum dots. The density of dopants is shown to be readily controllable,in analogy to atomic doping. The inclusion of dopants in the quantum dot solid is shown to vary the electronic conductivity of the film over six orders of magnitude as charge percolation pathways form in the lattice.

The effects of inorganic surface treatments on photogenerated carrier mobility and lifetime in PbSe quantum dot thin films

We used flash-photolysis, time-resolved microwave conductivity (TRMC) to probe the carrier mobility and lifetime in PbSe quantum dot (QD) thin films treated with solutions of the metal salts of Na2Se and PbCl2. The metal salt treatments tuned the Pb:Se stoichiometry and swept the Fermi energy throughout the QD thin film bandgap. The increase in TRMC mobility as the Fermi energy was shifted toward the band edges by non-stoichiometry is consistent with the QD thin film density of states.

Large-Area Nanoimprinted Colloidal Au Nanocrystal-Based Nano-antennas for Ultrathin Polarizing Plasmonic Metasurfaces

We report a low-cost, large-area fabrication process using solution-based nanoimprinting of colloidal Au nanocrystals to define anisotropic nanoinclusions for optical metasurfaces. We fabricate rod-shaped nano-antennas tailored in size and spacing to demonstrate Au nanocrystal-based quarter-wave plates that operate with extreme bandwidths and provide high polarization conversion efficiencies in the near-to-mid infrared.


Congratulations TJ!

TJ has been appointed Asst. Professor of the School of Integrative Engineering at Chung-Ang University. Congratulations, and good luck!

Congratulations to Ed Goodwin!

Ed has successfully defended his thesis, and shall now be known only as Dr. Goodwin. Congrats!

Congratulations to our Graduating Students!

Our graduating students will be continuing their education:
  • Emily - PhD program in MSE at Univ. of Michigan
  • Devika - PhD program in MSE at UT Austin
  • Matt - PhD program in EE at UC Berkeley
  • Prashanth - PhD program in EE at Univ. of Utah
  • Chawit - PhD program in Integrated in Photonic and Electronic Systems at Cambridge University

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Electrical & Systems Engineering, Moore Building
200 South 33rd Street, Philadelphia, PA 19104