Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 14: Struktur und Dynamik reiner Oberfl
ächen

O 14.2: Vortrag

Freitag, 4. März 2005, 16:00–16:15, TU EB407

Temporal evolution of surface structures after fs-laserpulse excitation — •B. Krenzer, A. Janzen, and M. Horn-von Hoegen — Fachbereich Physik, Universität Duisburg-Essen, Universitätsstr. 5, 45117 Essen

Studies of surface-dynamics with fs-timeresolution are very well established using optical methods, e.g. SHG, SFG. Structural informations of the investigated systems, however, are only indirectly accessible. Using ultrashort X-ray pulses a direct determination of bulk structures and their dynamics is possible [1]. The highly enhanced surface sensitivity and higher scattering amplitude of electrons made the development of timeresolved electron diffraction for surface studies desirable. Recently, the construction of electron guns providing fs-electron pulses has been achieved. This progress allows studies of structural changes of thin metal films and adsorbate systems on a ps- to sub-ps timescale [2].

We built an electron diffraction system capable to study surface dynamics. Short electronpulses are directed at glancing angle on surfaces excited by a fs-laserpulse. Depending on the delay between pumping laserpulse and probing electronpulse on the surface the temporal evolution of surface structures can be determined on a ps-timescale (ps-RHEED). In this talk we will present first results obtained with the new system. These investigations were conducted on clean and Bi-covered Si(001)-surfaces.

[1] K. Sokolowski-Tinten et. al., Nature 422, 286 (2003).

[2] B.J. Siwick et. al., Science 302, 1382 (2003), C.-Y. Ruan et. al., Science 304, 80 (2004).