Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 89: Metal Substrates: Epitaxy and Growth

O 89.1: Vortrag

Freitag, 29. Februar 2008, 09:30–09:45, MA 041

Real time observation of multiphoton photoemission and surface second harmonic generation during the growth of Fe on Cu(001) — •Cheng-Tien Chiang, Aimo Winkelmann, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle(Saale), Germany

We observed simultaneously the multiphoton photoemission and second harmonic generation (SHG) at 3.1 eV incident photon energy during the growth of Fe on Cu(001). The well-known intensity variations observable in medium energy electron diffraction measurements of Fe/Cu(001) were correlated with the variations of the SHG signal. Using SHG as a reference, we assign the different phases of the Fe growth to the observed photoemission spectra. With this approach, we obtain the work function variations as a function of film thickness from the photoemission spectra. For the first 4 monolayers (ML) of Fe deposited on Cu(001), a non-monotonic variation of the work function is observed, with a decrease of 0.14 eV for 1 ML Fe. This value is consistent with theoretical calculations [1]. In correspondence to the work function variations, a resonant three-photon photoemission (3PP) feature oscillates in intensity as a result of the fixed relationship between the vacuum level and an intermediate image potential state. From the exponentially decaying part of 3PP signal we can estimate the inelastic mean free path of electrons with kinetic energy of 4 eV above the Fermi level to be about 10Å.

[1] S. Achilli et al., J. Phys.:Condens. Matter 19, 305021 (2007)