Ultra-fast electron diffraction at surfaces: From nanoscale heat transport to driven phase transitions

Hanisch-Blicharski, Anja; Janzen, A.; Krenzer, B.; Wall, Simone; Klasing, F.; Kalus, Annika; Frigge, T.; Kammler, M.; Hoegen, M. Horn‐von

doi:10.1016/j.ultramic.2012.07.017

Cited by 46 publications

(32 citation statements)

References 113 publications

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“…We employed a time-resolved reflection high-energy electron diffraction (RHEED) technique implemented in a conventional pump-probe scheme to follow the ultrafast structural dynamics 25 . The electron energy was E = 30 keV at an angle of incidence of

ϑ = 1.7 °

.…”

Section: Experimental Setup and Sample Preparationmentioning

confidence: 99%

Non-equilibrium lattice dynamics of one-dimensional In chains on Si(111) upon ultrafast optical excitation

Frigge

Hafke

Witte

et al. 2018

Structural Dynamics

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The photoinduced structural dynamics of the atomic wire system on the Si(111)-In surface has been studied by ultrafast electron diffraction in reflection geometry. Upon intense fs-laser excitation, this system can be driven in around 1 ps from the insulating false(8×2false) reconstructed low temperature phase to a metastable metallic false(4×1false) reconstructed high temperature phase. Subsequent to the structural transition, the surface heats up on a 6 times slower timescale as determined from a transient Debye-Waller analysis of the diffraction spots. From a comparison with the structural response of the high temperature false(4×1false) phase, we conclude that electron-phonon coupling is responsible for the slow energy transfer from the excited electron system to the lattice. The significant difference in timescales is evidence that the photoinduced structural transition is non-thermally driven.

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ϑ = 1.7 °

.…”

Section: Experimental Setup and Sample Preparationmentioning

confidence: 99%

Non-equilibrium lattice dynamics of one-dimensional In chains on Si(111) upon ultrafast optical excitation

Frigge

Hafke

Witte

et al. 2018

Structural Dynamics

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“…For the investigation of the atomic structure at surfaces, mainly two pathways are currently followed: On the one hand, extremely thin films are probed by ultrafast TEM (UTEM) [131] and ultrafast electron diffraction (UED) [132] in transmission. To obtain a strong surface signal, a grazing incidence geometry is alternatively applied as in time-resolved XRD [133] and RHEED [44] studies.…”

Section: Motivationmentioning

confidence: 99%

“…Existing time-resolved surface studies have demonstrated the richness of ultrafast phenomena in quasi-two-dimensional systems excited to states far from equilibrium, including phonon confinement effects in ultrathin films [134], the relaxations of surface reconstructions and complex superstructures in monolayer adsorbate systems [44,135], surface pre-melting [136], and the formation of warm dense matter as a result of a strong coupling between electronic and lattice systems [137].…”

Section: Motivationmentioning

confidence: 99%

“…Depending on the probe, high surface sensitivity can be in principle achieved by using either large angles of incidence, as in XRD and reflection high-energy electron diffraction (RHEED) [44], or low kinetic electron energies. Large angles of incidence, however, have the disadvantage to be strongly dependent on the surface morphology, which makes a quantitative analysis difficult.…”

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Development of an Ultrafast Low-Energy Electron Diffraction Setup

Gulde

2015

Springer Theses

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“…The Pb forms 3-dimensional islands upon a disordered Pb wetting layer on the Si(111) surface. The islands are atomically flat with a width of few 10 µm [11]. At 3° angle of incidence of the electron beam, two strong diffraction spots were observed as depicted in the inset of Fig.…”

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confidence: 91%

Ultrafast time resolved reflection high energy electron diffraction with tilted pump pulse fronts

Zhou

Streubühr

Kalus

et al. 2013

EPJ Web of Conferences

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Abstract. We present time-resolved RHEED from a laser excited Pb(111) surface using a pulse front tilter for the compensation of the velocity mismatch of electrons and light. The laser pulses with tilted fronts were characterized by a spatially resolving cross correlator. The response of the surface upon excitation was observed to be less than 2 ps.Ultrafast electron diffraction is a promising technique for studying the dynamics of the atomic structure on a sub-picosecond time scale. Time resolved transmission electron diffraction (TR-TED) has been used, for example, to study bulk phenomena such as ultrafast laser-induced structural phase transitions [1], cooperative rearrangement of crystalline structures [2], and dynamics of charge density waves [3]. Time resolution of less than 100 fs [4] has been achieved. Time resolved reflection high energy electron diffraction (TR-RHEED), on the other hand, has been used for the investigation of ultrafast surface dynamics, for example the observation of ultrafast heating of surfaces [5], the heat transfer in hetero structures [6] and laser-induced phase transition of the surface reconstructions [7]. However, the time resolution in these experiments was limited to tens of picoseconds because of the different velocities of electrons and light in combination with the grazing angle of incidence of the electron beam in RHEED geometry.This velocity mismatch can be overcome and the time resolution significantly improved by tilting the laser pulse front with respect to the phase fronts. Baum et al. [8] have demonstrated a configuration for pulse front tilting and achieved an improvement of the temporal resolution to less than one picosecond. Here we report the use of a 4f zero dispersion delay line capable of matching the pulse front of the laser to the electron pulse. The improvement of the temporal resolution is demonstrated by measuring the ultrafast lattice heating of Pb(111) islands on a Si(111) surface.Generally speaking, when a laser pulse encounters angular dispersion, the planes of constant amplitude (intensity) will be tilted with respect to the planes of constant phase, for example when the pulse is reflected from a diffraction grating [9]. The pulse then broadens during the free propagation after the dispersive component. The broadening is reversed and the original pulse width restored by passing the pulse through the two lenses in a 4f configuration. Our pulse tilter was designed to compensate the velocity mismatch for 30 keV electrons. Based on the results of our electron source [10] a temporal resolution of better than 700 fs is expected.In order to independently control and characterize the tilted pulse we used a cross-correlator based on second harmonic generation (SHG). The special feature of this cross-correlator is the possibility to perform spatially resolved measurements of the cross-correlation function between the This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, dis...

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Ultra-fast electron diffraction at surfaces: From nanoscale heat transport to driven phase transitions

Cited by 46 publications

References 113 publications

Non-equilibrium lattice dynamics of one-dimensional In chains on Si(111) upon ultrafast optical excitation

Non-equilibrium lattice dynamics of one-dimensional In chains on Si(111) upon ultrafast optical excitation

Development of an Ultrafast Low-Energy Electron Diffraction Setup

Ultrafast time resolved reflection high energy electron diffraction with tilted pump pulse fronts

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