Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 82: Ultrafast Phenomena
HL 82.2: Vortrag
Donnerstag, 17. März 2011, 14:45–15:00, POT 251
Ultrafast Dynamics of ZnO and ZnO-BaTiO3 thin films — •Snigdhatanu Acharya1, Sumedha Chouthe1, Tammo Böntgen2, Rüdiger Schmidt-Grund2, Marius Grundmann2, and Gerhard Seifert1 — 1Institute of Physics, Martin-Luther-University, Halle-Wittenberg, Von-Danckelmann Platz 3, D-06120, Halle, Germany. — 2Institute for Experimental Physics-II, University of Leipzig, Linnestraße 5, D-04103 Leipzig, Germany.
Femtosecond pump-probe spectroscopy was performed at room temperature on ZnO thin film and a double layer thin film structure of BaTiO3/ZnO, to investigate coupling between the layers via the charge carrier dynamics. Frequency-doubled Ti:Sa laser pulses (150fs, 400nm) were used as pump; induced transmission changes were probed by supercontinuum (320-600nm) fs pulses. For ZnO, two photon absorption as well as direct excitation to the trap states close to the conduction band edge leads to transfer of carriers to the conduction band. The displaced carriers relax rapidly to the bottom of conduction band, and bleaching at 375nm attributed to population of discrete exciton A is observed. Further increase in the density at exciton levels lead to a stimulated emission at ~390 nm due to exciton-exciton scattering. Changes in refractive index induced by pump-pulse generates interferometric transmission changes between 400-600 nm. Similar contributions to the transient spectra are observed in BaTiO3/ZnO. BaTiO3 does not show any femtosecond response. Difference in the dynamical behaviour of the contributions in ZnO and BaTiO3/ZnO gives an indication of coupling between ZnO and BaTiO3.