Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)
O 27.111: Poster
Dienstag, 24. März 2009, 18:30–21:00, P2
Femtosecond electron dynamics in atomic wires: Si(557)-Au — •Kerstin Biedermann1, Tilman K. Rügheimer1, Thomas Fauster1, and Franz J. Himpsel2 — 1Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen — 2Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison WI 53706, USA
Recent experiments on Si(557)-Au have proven the existence of a spin-split surface state band below EF [1] and have provided first information on the unoccupied part of the electronic band structure [2,3]. The dynamics of electrons has not been investigated so far.
We have carried out time-resolved two-photon photoemission experiments using 37 fs infrared (IR, EIR=1.55 eV) and 55 fs ultraviolet (UV, EUV=4.65 eV) laser pulses. High intensity at 0.9 eV kinetic energy (work function Φ=4.88 eV) and time delay zero corresponds to an image-potential resonance [2,3] and has a lifetime of less than 10 fs. At lower kinetic energies the intensity spreads towards positive as well as negative time delays indicating contributions from several transitions. An intensity pile-up at positive delays (IR before UV) indicates an indirect filling of a state in the bulk band gap of the Si(557) substrate by two long-lived states. We present a detailed analysis of the data by fitting the spectra with optical Bloch equations. Our interpretation involves electron scattering between several surface states.
[1] I. Barke et al., Phys. Rev. Lett. 97, 226405 (2006)
[2] J. A. Lipton-Duffin et al., Phys. Rev. B 73, 245418 (2006)
[3] T. K. Rügheimer et al., Phys. Rev. B 75, 121401 (2007)