The Experts below are selected from a list of 176937 Experts worldwide ranked by ideXlab platform
R Dwayne J Miller - One of the best experts on this subject based on the ideXlab platform.
-
optical fiber driven low energy Electron gun for time resolved streak Diffraction
EPJ Web of Conferences, 2019Co-Authors: Chiwon Lee, R Dwayne J Miller, Kassier H GuntherAbstract:The wave guiding feature of the optical fibre optical fibres is specifically exploited to construct a novel type of Electron gun to realize single-shot Low-Energy Electron Diffraction experiments with the sub-picosecond resolution for studying irreversible samples.
-
transmission low energy Electron Diffraction using double gated single nanotip field emitter
Applied Physics Letters, 2018Co-Authors: Chiwon Lee, Soichiro Tsujino, R Dwayne J MillerAbstract: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, 2020Co-Authors: Gero Storeck, Simon Vogelgesang, Jan Gerrit Horstmann, Theo Diekmann, K Rossnagel, Claus Ropers, G Von Witte, Sergey V YaluninAbstract: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, 2018Co-Authors: Simon Vogelgesang, Gero Storeck, Jan Gerrit Horstmann, Theo Diekmann, Murat Sivis, S Schramm, K Rossnagel, Sascha Schafer, Claus RopersAbstract: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, 2014Co-Authors: Max Gulde, Gero Storeck, Sascha Schafer, Simon Schweda, Manisankar Maiti, Alec M Wodtke, Claus RopersAbstract: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, 2014Co-Authors: Max Gulde, Gero Storeck, Sascha Schafer, Simon Schweda, Manisankar Maiti, Alec M Wodtke, Claus RopersAbstract: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.
M Nishijima - One of the best experts on this subject based on the ideXlab platform.
-
chemisorption and thermal decomposition of benzene on pd 110 high resolution Electron energy loss spectroscopy low energy Electron Diffraction and thermal desorption studies
The Journal of Physical Chemistry, 1991Co-Authors: M Fujisawa, T Sekitani, Yoshitada Morikawa, M NishijimaAbstract:The adsorbed state of benzene on Pd(110) at 300 K and its thermal decomposition process in the temperature region up to 700 K have been investigated by using high-resolution Electron energy loss spectroscopy, Low-Energy Electron Diffraction, and multiplexed thermal desorption spectroscopy. Vibrational spectra show the existence of two adsorbed states of benzene on Pd(110) at 300 K. In one state, benzene is adsorbed with its C ring nearly parallel to the surface (flat benzene), and in the other state, at some angle (tilted benzene). The tilted benzene is located in the c(4{times}2) domains. For a small exposure ({approx lt}0.3 langmuir; fractional coverage {theta}{sub C{sub 6}H{sub 6}}{approx lt}0.07), the flat benzene predominates. With increasing exposure, conversion from flat to tilted benzene occurs, and the amount of tilted benzene is increased relative to that of flat benzene. For the saturation exposure (3 langmuirs: {theta}{sub C{sub 6}H{sub 6}} {approximately} 0.27), the tilted benzene predominates; the flat benzene also exists. Thermal decomposition of benzene on Pd(110) has been studied in detail. For a small exposure (0.3 langmuir), heating to 380-600 K forms the C{sub x}H{sub y}(x {ge} 1, y = 0,1) species as the decomposition products. By heating the sample to 600 K, theymore » find only C adatoms exist on Pd(110). For the saturation exposure (3 langmuirs), by heating the sample to 400 K, they find the C(4{times}2) structure is well developed and the Pd(110) surface is mostly covered by tilted benzene. Heating to 400-650 K forms the C{sub x}H{sub y} (x = 1 or {ge} 3, y = 0,1) species. The decomposition temperature is shifted toward higher temperatures by the site-blocking effect of benzene admolecules themselves. The decomposition is accompanied by h{sub 2} desorption.« less
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, 2020Co-Authors: Gero Storeck, Simon Vogelgesang, Jan Gerrit Horstmann, Theo Diekmann, K Rossnagel, Claus Ropers, G Von Witte, Sergey V YaluninAbstract: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, 2018Co-Authors: Simon Vogelgesang, Gero Storeck, Jan Gerrit Horstmann, Theo Diekmann, Murat Sivis, S Schramm, K Rossnagel, Sascha Schafer, Claus RopersAbstract: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.
Gero Storeck - 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, 2020Co-Authors: Gero Storeck, Simon Vogelgesang, Jan Gerrit Horstmann, Theo Diekmann, K Rossnagel, Claus Ropers, G Von Witte, Sergey V YaluninAbstract: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, 2018Co-Authors: Simon Vogelgesang, Gero Storeck, Jan Gerrit Horstmann, Theo Diekmann, Murat Sivis, S Schramm, K Rossnagel, Sascha Schafer, Claus RopersAbstract: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, 2014Co-Authors: Max Gulde, Gero Storeck, Sascha Schafer, Simon Schweda, Manisankar Maiti, Alec M Wodtke, Claus RopersAbstract: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, 2014Co-Authors: Max Gulde, Gero Storeck, Sascha Schafer, Simon Schweda, Manisankar Maiti, Alec M Wodtke, Claus RopersAbstract: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.
