TY - JOUR A1 - Hanisch-Blicharski, Anja A1 - Janzen, Andreas A1 - Krenzer, Boris A1 - Wall, S. A1 - Klasing, Friedrich A1 - Kalus, Annika A1 - Frigge, Tim A1 - Kammler, Martin A1 - Horn-von Hoegen, Michael T1 - Ultra-fast electron diffraction at surfaces: from nanoscale heat transport to driven phase transitions JF - Ultramicroscopy N2 - 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. Y1 - 2013 U6 - https://doi.org/10.1016/j.ultramic.2012.07.017 VL - 127 SP - 2 EP - 8 PB - Elsevier ER - TY - JOUR A1 - Krenzer, Boris A1 - Hanisch-Blicharski, Anja A1 - Schneider, Paul A1 - Payer, Thomas A1 - Möllenbeck, Simone A1 - Osmani, O. A1 - Kammler, Martin A1 - Meyer, R. A1 - Horn-von Hoegen, Michael T1 - Phonon confinement effects in ultrathin epitaxial bismuth films on silicon studied by time-resolved electron diffraction JF - Physical Review B N2 - The transient temperature evolution of ultrathin bismuth films, epitaxially grown on a silicon single crystal, upon femtosecond laser excitation is studied by time-resolved electron diffraction. The exponential decay of the film temperature is explained by phonon reflection at the interface, which results in a strongly reduced thermal conduction in the cross plane of the layered system. The thermal boundary conductance is found to be as low as 1273 W/(K cm2). Model calculations, including phonon confinement effects, explain the linear relationship between the observed film-temperature decay constant and the film thickness. Even for 2.5 nm thin films the phonon transmission probability across the interface is given by bulk properties. Our simulations show that phonon confinement effects are negligible for bismuth-film thicknesses larger than 1 nm. Y1 - 2009 U6 - https://doi.org/10.1103/PhysRevB.80.024307 VL - 80 IS - 2 PB - APS ER - TY - JOUR A1 - Frigge, Tim A1 - Wall, S. A1 - Krenzer, Boris A1 - Wippermann, St. A1 - Sanna, Simone A1 - Klasing, Friedrich A1 - Hanisch-Blicharski, Anja A1 - Kammler, Martin A1 - Schmidt, Wolf Gero A1 - Horn-von Hoegen, Michael T1 - Abstract - A Reply to the Comment by H. Shim et al. JF - Physical review letters Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.111.149602 VL - 111 IS - 14 PB - American Physical Society ER -