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R Dwayne J Miller - One of the best experts on this subject based on the ideXlab platform.

  • transmission low Energy Electron Diffraction using double gated single nanotip field emitter
    Applied Physics Letters, 2018
    Co-Authors: Chiwon Lee, Soichiro Tsujino, R Dwayne J Miller
    Abstract:

    We explore the spatial coherence of double-gate single nanotip field emitters by low-Energy Electron Diffraction experiments in transmission mode. By producing collimated field emission pulses from the single nanotip cathode and irradiating a suspended monolayer graphene film without additional optics, we observed sharper and higher resolution Bragg Diffraction spots than a previous experiment using a nanotip array cathode. In particular, we found complete conservation of the size and the shape of the Diffraction spots with those of the incident beam on the sample. The result indicates that the transverse coherence of a nanofabricated double-gate single-tip emitter is much larger than a few nanometers as determined by the apparent Diffraction spot size and overall spatial resolution of the observed Diffraction pattern.We explore the spatial coherence of double-gate single nanotip field emitters by low-Energy Electron Diffraction experiments in transmission mode. By producing collimated field emission pulses from the single nanotip cathode and irradiating a suspended monolayer graphene film without additional optics, we observed sharper and higher resolution Bragg Diffraction spots than a previous experiment using a nanotip array cathode. In particular, we found complete conservation of the size and the shape of the Diffraction spots with those of the incident beam on the sample. The result indicates that the transverse coherence of a nanofabricated double-gate single-tip emitter is much larger than a few nanometers as determined by the apparent Diffraction spot size and overall spatial resolution of the observed Diffraction pattern.

Claus Ropers - One of the best experts on this subject based on the ideXlab platform.

  • structural dynamics of incommensurate charge density waves tracked by ultrafast low Energy Electron Diffraction
    Structural Dynamics, 2020
    Co-Authors: Gero Storeck, Simon Vogelgesang, Jan Gerrit Horstmann, Theo Diekmann, K Rossnagel, Claus Ropers, G Von Witte, Sergey V Yalunin
    Abstract:

    We study the non-equilibrium structural dynamics of the incommensurate and nearly commensurate charge-density wave (CDW) phases in 1T- TaS 2. Employing ultrafast low-Energy Electron Diffraction with 1 ps temporal resolution, we investigate the ultrafast quench and recovery of the CDW-coupled periodic lattice distortion (PLD). Sequential structural relaxation processes are observed by tracking the intensities of main lattice as well as satellite Diffraction peaks and the diffuse scattering background. Comparing distinct groups of Diffraction peaks, we disentangle the ultrafast quench of the PLD amplitude from phonon-related reductions of the Diffraction intensity. Fluence-dependent relaxation cycles reveal a long-lived partial suppression of the order parameter for up to 60 ps, far outlasting the initial amplitude recovery and Electron-phonon scattering times. This delayed return to a quasi-thermal level is controlled by lattice thermalization and coincides with the population of zone-center acoustic modes, as evidenced by a structured diffuse background. The long-lived non-equilibrium order parameter suppression suggests hot populations of CDW-coupled lattice modes. Finally, a broadening of the superlattice peaks is observed at high fluences, pointing to a non-linear generation of phase fluctuations.

  • phase ordering of charge density waves traced by ultrafast low Energy Electron Diffraction
    Nature Physics, 2018
    Co-Authors: Simon Vogelgesang, Gero Storeck, Jan Gerrit Horstmann, Theo Diekmann, Murat Sivis, S Schramm, K Rossnagel, Sascha Schafer, Claus Ropers
    Abstract:

    A tracing of the phase-ordering kinetics of a charge density wave system demonstrates the potential of ultrafast low-Energy Electron Diffraction for studying phase transitions and ordering phenomena at surfaces and in low-dimensional systems.

  • ultrafast low Energy Electron Diffraction in transmission resolves polymer graphene superstructure dynamics
    Science, 2014
    Co-Authors: Max Gulde, Gero Storeck, Sascha Schafer, Simon Schweda, Manisankar Maiti, Alec M Wodtke, Claus Ropers
    Abstract:

    Two-dimensional systems such as surfaces and molecular monolayers exhibit a multitude of intriguing phases and complex transitions. Ultrafast structural probing of such systems offers direct time-domain information on internal interactions and couplings to a substrate or bulk support. We have developed ultrafast low-Energy Electron Diffraction and investigate in transmission the structural relaxation in a polymer/graphene bilayer system excited out of equilibrium. The laser-pump/Electron-probe scheme resolves the ultrafast melting of a polymer superstructure consisting of folded-chain crystals registered to a free-standing graphene substrate. We extract the time scales of Energy transfer across the bilayer interface, the loss of superstructure order, and the appearance of an amorphous phase with short-range correlations. The high surface sensitivity makes this experimental approach suitable for numerous problems in ultrafast surface science.

  • polymer superstructure dynamics on free standing graphene resolved by ultrafast low Energy Electron Diffraction
    19th International Conference on Ultrafast Phenomena (2014) paper 10.Thu.E.5, 2014
    Co-Authors: Max Gulde, Gero Storeck, Sascha Schafer, Simon Schweda, Manisankar Maiti, Alec M Wodtke, Claus Ropers
    Abstract:

    A newly developed technique for time-resolved surface science, ultrafast low-Energy Electron Diffraction (ULEED), resolves the melting dynamics of a stripe-like polymer superstructure adsorbed on free-standing graphene.

B Stritzker - One of the best experts on this subject based on the ideXlab platform.

  • reflection high Energy Electron Diffraction oscillations modulated by laser pulse deposited yba2cu3o7 x
    Physical Review Letters, 1992
    Co-Authors: H Karl, B Stritzker
    Abstract:

    Reflection high-Energy Electron Diffraction oscillations during pulsed laser ablation of YBa 2 Cu 3 O 7-x on SrTiO 3 (100) substrates were measured. We have found for the first time that the oscillations are modulated by the laser-pulse repetition frequency. Each laser pulse deposits 0.14 nm of material. This causes the specularly reflected intensity to decrease instantaneously, but then it increases exponentially due to crystallization

  • reflection high Energy Electron Diffraction oscillations modulated by laser pulse deposited yba2cu3o7 x
    Physical Review Letters, 1992
    Co-Authors: H Karl, B Stritzker
    Abstract:

    Reflection high-Energy Electron Diffraction oscillations during pulsed laser ablation of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$ on ${\mathrm{SrTiO}}_{3}$(100) substrates were measured. We have found for the first time that the oscillations are modulated by the laser-pulse repetition frequency. Each laser pulse deposits 0.14 nm of material. This causes the specularly reflected intensity to decrease instantaneously, but then it increases exponentially due to crystallization. An activation Energy of 0.7\ifmmode\pm\else\textpm\fi{}0.1 eV and a diffusion constant of 1.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}12}$ ${\mathrm{cm}}^{2}$/sec at 720\ifmmode^\circ\else\textdegree\fi{}C for the formation of c-axis oriented films was determined.

Simon Vogelgesang - One of the best experts on this subject based on the ideXlab platform.

  • structural dynamics of incommensurate charge density waves tracked by ultrafast low Energy Electron Diffraction
    Structural Dynamics, 2020
    Co-Authors: Gero Storeck, Simon Vogelgesang, Jan Gerrit Horstmann, Theo Diekmann, K Rossnagel, Claus Ropers, G Von Witte, Sergey V Yalunin
    Abstract:

    We study the non-equilibrium structural dynamics of the incommensurate and nearly commensurate charge-density wave (CDW) phases in 1T- TaS 2. Employing ultrafast low-Energy Electron Diffraction with 1 ps temporal resolution, we investigate the ultrafast quench and recovery of the CDW-coupled periodic lattice distortion (PLD). Sequential structural relaxation processes are observed by tracking the intensities of main lattice as well as satellite Diffraction peaks and the diffuse scattering background. Comparing distinct groups of Diffraction peaks, we disentangle the ultrafast quench of the PLD amplitude from phonon-related reductions of the Diffraction intensity. Fluence-dependent relaxation cycles reveal a long-lived partial suppression of the order parameter for up to 60 ps, far outlasting the initial amplitude recovery and Electron-phonon scattering times. This delayed return to a quasi-thermal level is controlled by lattice thermalization and coincides with the population of zone-center acoustic modes, as evidenced by a structured diffuse background. The long-lived non-equilibrium order parameter suppression suggests hot populations of CDW-coupled lattice modes. Finally, a broadening of the superlattice peaks is observed at high fluences, pointing to a non-linear generation of phase fluctuations.

  • phase ordering of charge density waves traced by ultrafast low Energy Electron Diffraction
    Nature Physics, 2018
    Co-Authors: Simon Vogelgesang, Gero Storeck, Jan Gerrit Horstmann, Theo Diekmann, Murat Sivis, S Schramm, K Rossnagel, Sascha Schafer, Claus Ropers
    Abstract:

    A tracing of the phase-ordering kinetics of a charge density wave system demonstrates the potential of ultrafast low-Energy Electron Diffraction for studying phase transitions and ordering phenomena at surfaces and in low-dimensional systems.

M Iiyama - One of the best experts on this subject based on the ideXlab platform.