||Dr. A. Weber-Bargioni
Molecular Foundry, Lawrence Berkeley, National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720
September 26, 2013
4:30pm, ME 1061
Investigating the propagation of optically excited states and optoelectronic processes in nano building block assemblies
Abstract: Controlling individual excited states and their deliberate movement through a material is one of the ultimate goals that will provide material scientist with a complete new freedom to develop novel material functionalities. Nano materials have in principle the potential to realize this vision since the material property determining electronic structure can be tuned via geometry, material composition, interfaces and environment. However, the control of individual charges and excited states require band engineering that entails an entire new set of engineering rules for the nm world and the appropriate characterization techniques at the critical length scales. First I will present a novel approach to understand the local defect state introduced heterogeneity of local radiative charge recombination in individual InP nano wires using next generation near field optics and high resolution Kelvin Probe Microscopy. With the goal to excite and detect the emission of photons of nano materials with sub-diffraction limited spatial resolution we have been developing the so called "campanile" near field probe that comes close to the holy grail of near field optics: It enables excitation AND collection through a glass fiber, combined with enormous broadband near field enhancement and spatial resolution.
In the second part of my talk I will discuss our first efforts to map the transport of optically excited states through organic and inorganic nano building block assemblies. By using nano optics we excite locally our nano material composition and map spatially independent the energy flow by detecting either the local photo luminescence or the local photo current. The organic assemblies are small molecule OPV materials where we study exciton diffusion and means to reduce exciton binding energy. The inorganic assemblies are 1 and 2-D assembled CdSe Nano Crystal assemblies where we want to understand Foerster Resonant Energy Transport mechanisms.
Bio: Alexander Weber-Bargioni graduated from the University of Konstanz, received his PhD in physics from the University of British Columbia (2007), and did his postdoc at the Lawrence Berkeley National Laboratory. He is a staff scientist at the Molecular Foundry (LBNL), focusing on understanding and controlling fundamental optoelectronic processes at their respective length and time scale, utilizing advancements in plasmonics, near field imaging, and electronic structure and transport studies with molecular scale resolution.
Reception: 4:00 – 4:30 in Rail Station in Gatewood Wing