Frank-J. Meyer Zu Heringdorf

Publications (6)64.04 Total impact

• Article: Interplay of wrinkles, strain, and lattice parameter in graphene on iridium.

  Hichem Hattab, Alpha T N'Diaye, Dirk Wall, Claudius Klein, Giriraj Jnawali, Johann Coraux, Carsten Busse, Raoul van Gastel, Bene Poelsema, Thomas Michely, Frank-J Meyer zu Heringdorf, Michael Horn-von Hoegen
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  ABSTRACT: Following graphene growth by thermal decomposition of ethylene on Ir(111) at high temperatures we analyzed the strain state and the wrinkle formation kinetics as function of temperature. Using the moiré spot separation in a low energy electron diffraction pattern as a magnifying mechanism for the difference in the lattice parameters between Ir and graphene, we achieved an unrivaled relative precision of ±0.1 pm for the graphene lattice parameter. Our data reveals a characteristic hysteresis of the graphene lattice parameter that is explained by the interplay of reversible wrinkle formation and film strain. We show that graphene on Ir(111) always exhibits residual compressive strain at room temperature. Our results provide important guidelines for strategies to avoid wrinkling.
  Nano Letters 12/2011; 12(2):678-82. · 13.20 Impact Factor
• Source

  Available from: Carsten Busse

  Article: In situ observation of stress relaxation in epitaxial graphene

  Alpha T. N'Diaye, Raoul van Gastel, Antonio J. Martinez-Galera, Johann Coraux, Hichem Hattab, Dirk Wall, Frank-J. Meyer Zu Heringdorf, Michael Horn-von Hoegen, Jose M. Gomez-Rodriguez, Bene Poelsema, Carsten Busse, Thomas Michely
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  ABSTRACT: Upon cooling, branched line defects develop in epitaxial graphene grown at high temperature on Pt(111) and Ir(111). Using atomically resolved scanning tunneling microscopy we demonstrate that these defects are wrinkles in the graphene layer, i.e. stripes of partially delaminated graphene. With low energy electron microscopy (LEEM) we investigate the wrinkling phenomenon in situ. Upon temperature cycling we observe hysteresis in the appearance and disappearance of the wrinkles. Simultaneously with wrinkle formation a change in bright field imaging intensity of adjacent areas and a shift in the moire spot positions for micro diffraction of such areas takes place. The stress relieved by wrinkle formation results from the mismatch in thermal expansion coefficients of graphene and the substrate. A simple one-dimensional model taking into account the energies related to strain, delamination and bending of graphene is in qualitative agreement with our observations. Comment: Supplementary information: S1: Photo electron emission microscopy and LEEM measurements of rotational domains, STM data of a delaminated bulge around a dislocation. S2: Movie with increasing brightness upon wrinkle formation as in figure 4. v2: Major revision including new experimental data
  06/2009;
• Article: Electronic acceleration of atomic motions and disordering in bismuth.

  Germán Sciaini, Maher Harb, Sergei G Kruglik, Thomas Payer, Christoph T Hebeisen, Frank-J Meyer zu Heringdorf, Mariko Yamaguchi, Michael Horn-von Hoegen, Ralph Ernstorfer, R J Dwayne Miller
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  ABSTRACT: The development of X-ray and electron diffraction methods with ultrahigh time resolution has made it possible to map directly, at the atomic level, structural changes in solids induced by laser excitation. This has resulted in unprecedented insights into the lattice dynamics of solids undergoing phase transitions. In aluminium, for example, femtosecond optical excitation hardly affects the potential energy surface of the lattice; instead, melting of the material is governed by the transfer of thermal energy between the excited electrons and the initially cold lattice. In semiconductors, in contrast, exciting approximately 10 per cent of the valence electrons results in non-thermal lattice collapse owing to the antibonding character of the conduction band. These different material responses raise the intriguing question of how Peierls-distorted systems such as bismuth will respond to strong excitations. The evolution of the atomic configuration of bismuth upon excitation of its A(1g) lattice mode, which involves damped oscillations of atoms along the direction of the Peierls distortion of the crystal, has been probed, but the actual melting of the material has not yet been investigated. Here we present a femtosecond electron diffraction study of the structural changes in crystalline bismuth as it undergoes laser-induced melting. We find that the dynamics of the phase transition depend strongly on the excitation intensity, with melting occurring within 190 fs (that is, within half a period of the unperturbed A(1g) lattice mode) at the highest excitation. We attribute the surprising speed of the melting process to laser-induced changes in the potential energy surface of the lattice, which result in strong acceleration of the atoms along the longitudinal direction of the lattice and efficient coupling of this motion to an unstable transverse vibrational mode. That is, the atomic motions in crystalline bismuth can be electronically accelerated so that the solid-to-liquid phase transition occurs on a sub-vibrational timescale.
  Nature 04/2009; 458(7234):56-9. · 36.28 Impact Factor
• Article: Au stabilization and coverage of sawtooth facets on Si nanowires grown by vapor-liquid-solid epitaxy.

  Christian Wiethoff, Frances M Ross, Matthew Copel, Michael Horn-von Hoegen, Frank-J Meyer Zu Heringdorf
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  ABSTRACT: Si nanowires grown in UHV by Au-catalyzed vapor-liquid-solid epitaxy are known to exhibit sidewalls with {112}-type orientation that show faceting. To understand the origin of the faceting, Au induced faceting on Si(112) surfaces was studied in situ by spot-profile-analyzing low-energy electron diffraction. With increasing Au coverage at 750 degrees C, the Si(112) surface undergoes various morphological transformations until, at a critical Au coverage of about 3.1 x 10 (14) atoms/cm (2), a phase consisting of large (111) and (113) facets forms, similar in structure to the nanowire sidewalls. This phase is stable at larger Au coverages in equilibrium with Au droplets. We suggest that Si nanowire surfaces exhibit this structure, and we derive the Au coverage on the two types of facets.
  Nano Letters 10/2008; 8(9):3065-8. · 13.20 Impact Factor
• Article: Reciprocal space mapping by spot profile analyzing low energy electron diffraction

  Frank-J. Meyer zu Heringdorf, Michael Horn-von Hoegen
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  ABSTRACT: We present an experimental approach for the recording of two-dimensional reciprocal space maps using spot profile analyzing low energy electron diffraction (SPA-LEED). A specialized alignment procedure eliminates the shifting of LEED patterns on the screen which is commonly observed upon variation of the electron energy. After the alignment, a set of one-dimensional sections through the diffraction pattern is recorded at different energies. A freely available software tool is used to assemble the sections into a reciprocal space map. The necessary modifications of the Burr-Brown computer interface of the two Leybold and Omicron type SPA-LEED instruments are discussed and step-by-step instructions are given to adapt the SPA 4.1d software to the changed hardware. Au induced faceting of 4° vicinal Si(001) is used as an example to demonstrate the technique.
  Review of Scientific Instruments 07/2005; 76(8):085102-085102-5. · 1.37 Impact Factor
• Source

  Available from: Carsten Busse

  Article: Growth of graphene on Ir(111)

  Johann Coraux, Alpha T. N'Diaye, Martin Engler, Carsten Busse, Dirk Wall, Niemma Buckanie, Frank-J. Meyer Zu Heringdorf, Raoul van Gastel, Bene Poelsema, Thomas Michely
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  ABSTRACT: Catalytic decomposition of hydrocarbons on transition metals attracts a renewed interest as a route toward high-quality graphene prepared in a reproducible manner. Here we employ two growth methods for graphene on Ir(111), namely room temperature adsorption and thermal decomposition at 870-1470 K (temperature programmed growth (TPG)) as well as direct exposure of the hot substrate at 870-1320 K (chemical vapor deposition (CVD)). The temperature- and exposure-dependent growth of graphene is investigated in detail by scanning tunneling microscopy. TPG is found to yield compact graphene islands bounded by C zigzag edges. The island size may be tuned from a few to a couple of tens of nanometers through Smoluchowski ripening. In the CVD growth, the carbon in ethene molecules arriving on the Ir surface is found to convert with probability near unity to graphene. The temperature-dependent nucleation, interaction with steps and coalescence of graphene islands are analyzed and a consistent model for CVD growth is developed.