Berlin 2012 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 12: Surface dynamics
O 12.12: Vortrag
Montag, 26. März 2012, 18:45–19:00, H 2013
Two-photon photoemission studies Germanium(100) - Binding energies, lifetimes and dispersion of the surface states — •Jens Kopprasch1,2, Kristof Zielke1,2, Cornelius Gahl1,2, Christian Eickhoff1,2, Jörg Schäfer3, and Martin Weinelt1,2 — 1Max-Born-Institut, Max-Born-Straße 2a, 12489 Berlin, Germany — 2Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany — 3Universitat Würzburg, Fakultät für Physik und Astronomie, Am Hubland, 97074 Würzburg, Germany
Germanium(Ge) has the same crystal structure as silicon (diamond-like) but opposite to Si the band gap is much smaller (0.67 eV at 300 K) and has a local minimum at the Γ-point. This difference in band structure leads to a growing interest of Ge in semiconductor industry, where it is used for solar cells, high-power transistors, infrared optics and x-ray detectors.
The surface reconstruction on Ge(100) is also comparable to Si(100). This leads to the so-called dangling-bond states Dup and Ddown. By using two-photon-photoemission (2PPE) spectroscopy we observed both surface states and could identify the first image-potential state n=1. Binding energies, lifetimes and dispersion of these states will be presented. Measurements at 90K within a range of k∥=±0.5 Å−1 and a maximum time delay of 50ps show the conduction band minimum and a number of transitions among the bulk bands. We will present this measurements and discuss their origin and the concomitant carrier dynamics.