Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 22: Epitaxie und Wachstum I
O 22.6: Vortrag
Dienstag, 25. März 2003, 16:15–16:30, FOE/ORG
Image-potential states on ultrathin nickel films on Cu(001) — •Martin Pickel1,2, Jinxiong Wang2, Anke Schmidt2, Martin Weinelt2, and Markus Donath1 — 1Physikalisches Institut, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — 2Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen
The electronic structure and dynamics of image-potential states can be used as sensors for surface properties, e.g. the growth and morpholgy of metal overlayers. We investigate the first image-potential state on ultrathin nickel films grown on a Cu(001) substrate by two-photon photo-emission (2PPE).
At a coverage below one monolayer we observe only one image-potential state and not two individual peaks, corresponding to the substrate and the overlayer. This can be attributed to a high nucleation density of nickel on Cu(001). At higher coverages a narrow linewidth of the image-potential state indicates a good quality of the films. Beside the work function, the binding energy of the first image-potential state has been recorded up to several monolayers. Assuming a comparable population of spin-up and spin-down image-potential states, an upper limit of the spin splitting can be deduced. Time-resolved measurements reveal a lifetime of the electrons in the first image-potential state of 15±5 fs.