title: Ultra-fast electron diffraction at surfaces: from nanoscale heat transport to driven phase transitions.
abstract: Many fundamental processes of structural changes at surfaces occur on a pico- or femtosecond time scale. In order to study such ultra-fast processes, we have combined modern surface science techniques with fs-laser pulses in a pump-probe scheme. Reflection high energy electron diffraction (RHEED) with grazing incident electrons ensures surface sensitivity for the probing electron pulses. Utilizing the Debye-Waller effect, we studied the cooling of vibrational excitations in monolayer adsorbate systems or the nanoscale heat transport from an ultra-thin film through a hetero-interface on the lower ps-time scale. The relaxation dynamics of a driven phase transition far away from thermal equilibrium is demonstrated with the In-induced (8×2) reconstruction on Si(111). This surface exhibits a Peierls-like phase transition at 100K from a (8×2) ground state to (4×1) excited state. Upon excitation by a fs-laser pulse, this structural phase transition is driven into an excited (4×1) state at a sample temperature of 20K. Relaxation into the (8×2) ground state occurs after more than 150 ps.
authors.affiliation: Department of Physics and Center for Nanointegration CeNIDE, University of Duisburg-Essen, Lotharstrasse 1, Duisburg 47057, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Hanisch-Blicharski
authors.forename: A
authors.initials: A
authors.lastname: Janzen
authors.forename: B
authors.initials: B
authors.lastname: Krenzer
authors.forename: S
authors.initials: S
authors.lastname: Wall
authors.forename: F
authors.initials: F
authors.lastname: Klasing
authors.forename: A
authors.initials: A
authors.lastname: Kalus
authors.forename: T
authors.initials: T
authors.lastname: Frigge
authors.forename: M
authors.initials: M
authors.lastname: Kammler
authors.forename: M
authors.initials: M
authors.lastname: Horn-von Hoegen