Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 65: Time-resolved spectroscopies III
O 65.2: Vortrag
Freitag, 27. März 2009, 11:30–11:45, SCH A315
Ultrafast dynamics in Silicon studied at FLASH — •Martin Beye1, Alexander Föhlisch1, Florian Sorgenfrei1, Bill Schlotter1, Torben Beeck1, Annette Pietzsch2, Franz Hennies2, and Wilfried Wurth1 — 1Department Physik, Universität Hamburg, Deutschland — 2MAX-lab, Lund, Sweden
Soft X-ray spectroscopies at new light sources like the free electron LASER at Hamburg (FLASH), which provide pulses of some tens of fs length with unrivaled brilliances, provide new tools for the element specific analysis of ultrafast processes resolving local and long range symmetries. We present measurements on crystalline Silicon unraveling timescales of electronic and nuclear processes after specific excitations.
We either use an optical pump laser or the XUV pulses from FLASH to excite phonons, valence or core electrons, respectively. Their temporal evolution is tracked via X-ray emission spectroscopy of Silicon induced by variably delayed FLASH pulses. This shows the dynamics of the electronic system, resolves temporal changes in the bandstructure, in the electron distribution and of the orbital and crystal momentum.
Using the optical laser as a probe instead, we are sensitive to changes in the electronic structure around the bandgap and the long range structure of the crystal itself. We track those changes after X-ray excitation and their decay via different cascading electronic and phononic processes by analyzing transient reflectivity changes.
We acknowledge financial support from the BMBF priority program FSP301: "FLASH" and the GrK 1355 "Physics with new coherent light sources"