TY - JOUR A1 - Wall, Simone A1 - Krenzer, Boris A1 - Wippermann, Stefan A1 - Sanna, Simone A1 - Klasing, Friedrich A1 - Hanisch-Blicharski, Anja A1 - Kammler, Martin A1 - Schmidt, Wolf Gero A1 - Horn-von Hoegen, Michael T1 - Atomistic picture of charge density wave formation at surfaces JF - Physical review letters N2 - We used ultrafast electron diffraction and density-functional theory calculations to gain insight into the charge density wave (CDW) formation on In/Si(111). Weak excitation by a femtosecond-laser pulse results in the melting of the CDW. The immediate freezing is hindered by a barrier for the motion of atoms during the phase transition: The melted CDW constitutes a long-lived, supercooled phase and is strong evidence for a first-order transition. The freezing into the CDW is triggered by preexisting adsorbates. Starting at these condensation nuclei, the CDW expands one dimensionally on the In/Si(111) surface, with a constant velocity of more than 80 m/s. Y1 - 2012 U6 - https://doi.org/10.1103/PhysRevLett.109.186101 VL - 109 IS - 18 PB - APS ER - TY - JOUR A1 - Frigge, Tim A1 - Kalus, Annika A1 - Klasing, Friedrich A1 - Kammler, Martin A1 - Hanisch-Blicharski, Anja A1 - Horn-von Hoegen, Michael T1 - Nanoscale Heat Transport in Self-Organized Ge Clusters on Si(001) JF - MRS Online Proceedings Library N2 - Ultrafast time resolved transmission electron diffraction (TED) in a reflection geometry was used to study the cooling behavior of self-organized, well defined nanoscale germanium hut and dome clusters on Si(001). The clusters were heated in a pump-probe scheme by fs-laser pulses. The resulting transient temperature rise was then determined from the drop in diffraction intensity caused by the Debye-Waller effect. From a cooling time of τ=177 ps we estimated a strongly reduced heat transfer compared with homogeneous films of equivalent thickness. Y1 - 2012 U6 - https://doi.org/10.1557/opl.2013.148 SP - 45 EP - 50 PB - Springer ER - 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 - 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 -