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HL: Fachverband Halbleiterphysik

HL 109: Ultra-fast phenomena I

HL 109.1: Vortrag

Freitag, 4. April 2014, 09:30–09:45, POT 006

Visualization of ultrafast currents in nanowires by imaging with femtosecond low-energy electron pulses — •Melanie Müller, Alexander Paarmann, and Ralph Ernstorfer — Fritz-Haber-Institut der MPG, Berlin, Germany

We use a nanotip as laser-triggered low-energy electron point source (LEEPS) delivering coherent ultrashort electron pulses for time-resolved projection imaging of photoexcited nanostructures. Due to their high sensitivity to weak fields, low-energy electron pulses are particularly suited for mapping transient electric fields and charge distributions in nanostructures. Specifically, charge carrier separation upon above-bandgap excitation in doped nanowires (NWs) transiently induces local variations of the vacuum level, deflecting the electrons from their original trajectories. Operating our LEEPS microscope in a pump-probe scheme, we are able to probe ultrafast photocurrents in axially doped InP NWs with several 10 nm spatial and femtosecond temporal resolution.