Theory of grazing incidence diffraction of fast atoms and molecules from surfaces

Manson, J. R.; Khemliche, H.; Roncin, P.

doi:10.1103/physrevb.78.155408

Cited by 72 publications

(128 citation statements)

References 27 publications

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“…The diffraction of fast atoms from crystal surfaces under grazing incidence conditions has been the focus of extensive experimental and theoretical research [1][2][3][4][5][6][7][8][9][10][11][12][13][14] since its unexpected observation a few years ago [15,16]. From the theoretical point of view, different methods have been employed to simulate experimental data of this phenomenon, now known as grazing-incidence fast atom diffraction (GIFAD or FAD) [17].…”

Section: Introductionmentioning

confidence: 99%

Semiquantum approach for fast atom diffraction: Solving the rainbow divergence

Gravielle

Miraglia

2014

Phys. Rev. A

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In this work we introduce a distorted wave method, based on the Initial Value Representation (IVR) approach of the quantum evolution operator, in order to improve the semiclassical description of rainbow effects in diffraction patterns produced by grazing scattering of fast atoms from crystal surfaces. The proposed theory, named Surface Initial Value Representation (SIVR) approximation, is applied to He atoms colliding with a LiF(001) surface along low indexed crystallographic channels. For this collision system the SIVR approach provides a very good representation of the quantum interference structures of experimental projectile distributions, even in the angular region around classical rainbow angles where common semiclassical methods diverge.

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Section: Introductionmentioning

confidence: 99%

Semiquantum approach for fast atom diffraction: Solving the rainbow divergence

Gravielle

Miraglia

2014

Phys. Rev. A

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“…The energy deposited into the lattice for the parameters used above (∼2.56 meV, which is on the order of the results given by Manson et al [16] for grazing angle collisions) is far smaller than the energy spread in typical helium scattering experiments; as mentioned earlier, the low-energy phonon modes that are excited can be masked by the small total energy change from the lattice nuclear stopping power.…”

Section: B Phonon Excitationsmentioning

confidence: 78%

“…While the surface atoms are at any instant displaced from their equilibrium positions (effectively eliminating the constructive interference condition at any instant), the mean atomic positions are still at the sites indexed by the crystal lattice. We thus still observe diffraction spots, although they are diminished by either an effective Debye-Waller term or another factor depending on the scattering conditions [15,16]. The description of scattering remains coherent.…”

Section: Introductionmentioning

confidence: 83%

“…This causes waves to ripple outward in the ±y directions of the lattice creating phonons, while the k x -momentum transfer is negligible due to the rapid attraction-repulsive cycles of the kicks off of the individual atoms in the lattice, parallel to the surface. Aigner et al [47] considered this aspect using a Lindblad master equation formulation with a Monte Carlo ensemble of trajectories to understand the system dynamics and decrease in self-coherence length and observed that the potential parallel to the direction of motion became effectively averaged out; Manson et al [16] described a similar effect in that the fast motion would act as effectively classical dynamics, while the slower motion is more appropriate to describe via quantum dynamics. This effect explains the robustness of our potential model with respect to the parameters we used.…”

Section: B Phonon Excitationsmentioning

confidence: 99%

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Approach to coherent interference fringes in helium-surface scattering

Schram

Heller

2018

Phys. Rev. A

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The conventional notion of elastic, coherent atom-surface scattering originates from the scattering particles acting as a quantum-mechanical matter wave, which coherently interfere to produce distinct Bragg peaks which persist at finite temperature. If we introduce inelastic scattering to this scenario, the result is that the surface particles become displaced by the scattering atoms, resulting in emission or absorption of phonons that shift the final energy and momentum of the scatterer. As the lowest-lying phonons are gapless excitations, the ability to measure these phonons is very difficult and this difficulty is exacerbated by the roughly 1-eV resolution found in high-energy helium scattering experiments. Even though the surface has in effect measured the presence of the scatterer which decoheres the particle, we retain the diffraction spots which are referred to as coherent scattering. How do we reconcile these disparate viewpoints? We propose an experiment to more precisely examine the question of coherence in atom-surface scattering. We begin with an initially coherent superposition of helium particles with equal probabilities of interacting with the surface or not interacting with the surface. The beams are directed so that after the scattering event, the atoms are recombined so that we can observe the resulting interference pattern. The degree to which phonons are excited in the lattice by the scattering process dictates the fringe contrast of the interference pattern of the resulting beams. We use semiclassical techniques to simulate and test the viability of this experiment and show that for a wide range of conditions, despite the massive change in the momentum perpendicular to the surface, we can still expect to have coherent (in the superposition sense) scattering.

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“…In GIFAD these spots inherit the profile as the incident beam. In addition, the inelastic background produced by the thermal movement of the surface atoms 9,17 , and by the surface defects 22 gives rise to a low intensity vertical extensions of the spots as can be seen on Fig. 1.…”

Section: Experimental Setup Mbe and Gifadmentioning

confidence: 86%

Fast atom diffraction inside a molecular beam epitaxy chamber, a rich combination

Debiossac

Atkinson

Zugarramurdi

et al. 2017

Applied Surface Science

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Two aspects of the contribution of grazing incidence fast atom diffraction (GIFAD) to molecular beam epitaxy (MBE) are reviewed here: the ability of GIFAD to provide in-situ a precise description of the atomic-scale surface topology, and its ability to follow larger-scale changes in surface roughness during layer-by-layer growth. Recent experimental and theoretical results obtained for the He atom beam incident along the highly corrugated [110] direction of the β 2 (2×4) reconstructed GaAs(001) surface are summarized and complemented by the measurements and calculations for the beam incidence along the weakly corrugated [010] direction where a periodicity twice smaller as expected is observed. The combination of the experiment, quantum scattering matrix calculations, and semiclassical analysis allows in this case to reveal structural characteristics of the surface. For the in situ measurements of GIFAD during molecular beam epitaxy of GaAs on GaAs surface we analyse the change in elastic and inelastic contributions in the scattered beam, and the variation of the diffraction pattern in polar angle scattering. This analysis outlines the robustness, the simplicity and the richness of the GIFAD as a technique to monitor the layer-by-layer epitaxial growth.

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Theory of grazing incidence diffraction of fast atoms and molecules from surfaces

Cited by 72 publications

References 27 publications

Semiquantum approach for fast atom diffraction: Solving the rainbow divergence

Semiquantum approach for fast atom diffraction: Solving the rainbow divergence

Approach to coherent interference fringes in helium-surface scattering

Fast atom diffraction inside a molecular beam epitaxy chamber, a rich combination

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