Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 37: Posters: Plasmonics, Electronic Structure and Spin-Orbit Interaction, Semiconductor and Insulator Surfaces, Nanostructures
O 37.34: Poster
Dienstag, 1. April 2014, 18:30–22:00, P2
Pump-probe infrared near-field nanospectroscopy on germanium and silicon — •Frederik Kuschewski1, S.C. Kehr1, B. Green2, Ch. Bauer2,3, M. Gensch2, and L.M. Eng1 — 1Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden, Germany — 2Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany — 3Freie Universität Berlin, 14195 Dahlem, Germany
Scattering-type scanning near-field optical microscopy (s-SNOM) was applied to investigate the local infrared-optical properties of germanium, silicon and SiGe thin film in a pump-probe experiment below the diffraction limit. The novel combination of s-SNOM with pump-probe techniques allows us to study electron excitation processes at an ultimate temporal resolution and to investigate their decay behavior.
Our s-SNOM is based on a non-contact atomic force microscope. The optical near-field is demodulated at higher-harmonics, which is extended to a novel side-band demodulation technique that allows for the direct measurement of pump-induced effects. Pump excitation is exhibited with a Nd:YAG ps laser while near-field probing was carried out either by a cw CO2 laser or by the tuneable FELBE free-electron-laser at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR).
All three samples show a clear time-variable pump-effect in the near-field when being probed at ∼ 10 µm wavelenght. Image scans clearly proof the resolution far beyond the diffraction limit. The experiment provides a definite proof of the applicability of our approach for investigating ultrafast phenomena in the near-field.