Regensburg 2019 – scientific programme

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O: Fachverband Oberflächenphysik

O 85: Ultrafast Electron Dynamics at Surfaces and Interfaces II: New Methods and Developments

O 85.4: Talk

Thursday, April 4, 2019, 15:45–16:00, H16

Visualization of Charge Carrier Motion in Nanosystems by Point-projection Microscopy — •Ivana Lapšanská, Faruk Krecinic, Melanie Müller, and Ralph Ernstorfer — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

The ultrafast motion of charge carriers at the nanoscale plays a crucial role in the understanding and development of new optoelectronic devices. To visualize nanoscale dynamics, we employ femtosecond point projection microscopy (fs-PPM) - a technique based on low-energy (<200 eV) electron imaging in a pump-probe configuration. Probe electrons are photo-emitted from a nanotip by a femtosecond laser pulse, and diverge towards a sample producing an enlarged image of the electrostatic environment of a nanoscale object. The sample is optically excited by a laser pulse and the induced charge motion can be visualized via the interaction of the low-energy electrons with the carrier motion-induced local electric fields. We obtain a temporal resolution of the dynamics of charge motion down to tens of femtoseconds, with a spatial resolution down to 10 nm. We demonstrate the concept of charge motion visualization for amorphous carbon nanostructures, graphene and III-V semiconductor nanowires.