Regensburg 2004 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
O: Oberflächenphysik
O 28: Postersitzung (Elektronische Struktur, Grenzfläche fest-flüssig, Halbleiteroberflächen und -grenzflächen, Magnetismus und Symposium SYXM, Methodisches, Nanostrukturen, Oberflächenreaktionen, Teilchen und Cluster, Zeitaufgelöste Spektroskopie)
O 28.70: Poster
Mittwoch, 10. März 2004, 16:00–19:00, Bereich C
Electron dynamics of buried interface states in Ar/Cu(100) probed by time-resolved two-photon photoemission — •M. Rohleder, W. Berthold, K. Duncker, J. Güdde, and U. Höfer — Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universtät, D-35032 Marburg
We demonstrate for the system Ar/Cu(100) how in favourable cases the dynamics of electronic states located at the interface between a metal and an insulator can be investigated by means of time-resolved two-photon photoemission (2PPE). The interface states of Ar/Cu are located above the vacuum level in the band gaps of both the Cu(100) surface and the Ar films which were as thick as 70 monolayers (ML). With increasing layer thickness the states evolve from quantum-well-like resonances into well-defined bound states which arise from the screened image-potential of the metal. Electrons excited into these states decay on timescales between 100 fs and 250 fs by electron-hole pair excitation in the metal and – for thin Ar layers (<20-30 ML) – also by electron transfer through the insulating Ar layers into the vacuum. In comparison to the image-potential states of the clean surface, the interface states are modified by the potential inside the dielectric layers. Screening reduces their binding energies with respect to the Ar conduction band and also results in longer lifetimes. The dispersion of the states is found to be parabolic near the band minimum with an effective mass of 0.5 me.