ECAMP 15

Hydrogen atom diffraction through free-standing single-layer graphene

Pierre Guichard,$^1$ Arnaud Dochain,$^2$ Raphaël Marion,$^{2,3}$ Pauline de Crombrugghe de Picquendaele,$^2$ Nicolas Lejeune,$^{2,4}$ Benoît Hackens,$^2$ Paul-Antoine Hervieux,$^1$ and Xavier Urbain $^2$

$^1$ Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504, 67000 Strasbourg, France
$^2$ Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
$^3$ Royal Observatory of Belgium (ROB-ORB), B-1180 Brussels, Belgium
$^4$ EPHEC, B-1348 Louvain-la-Neuve, Belgium

We report the observation of fast atom diffraction through single-layer graphene. High resolution images have been recorded with hydrogen atoms at kinetic energies ranging from 150 eV to 1200 eV, following the experimental protocol suggested by Brand et al. [1]. The commercial suspended graphene samples were characterized using micro-Raman spectroscopy, prior to and after beam exposure for the quantification of defects. When placed on the beam path in ultra-high vacuum, the samples were subjected to high temperature to induce thermal desorption of contaminants. Monocrystalline domains within the illuminated area produced characteristic hexagonal diffraction patterns. A negligible energy loss was recorded by time-of-flight tagging of individual atom detection events, making such an experimental approach suitable for matter-wave interferometry.
Density functional theory calculations with pseudopotentials [2] have been performed to determine the H-graphene interaction potential over the whole unit cell. The total energy of the system was calculated as a function of the position of the hydrogen atom relative to the graphene surface. The energies of the isolated graphene sheet and the hydrogen atom were then subtracted from the total energy of the system. Nice agreement with the calculations of Ehemann et al [3] is found, who used the Self-Consistent Charge-Density Functional Tight Binding method. In particular, our calculations confirm the presence of a long-range potential well reminiscent of the C-H bond. In order to simulate diffraction images, we generate a phase mask by integrating the three-dimensional potential along the coordinate normal to the graphene plane and performing an eikonal treatment of the scattering events.

[1] C. Brand, M. Debiossac, T. Susi, F. Aguillon, J. Kotakoski, P. Roncin, and M. Arndt, New Journal of Physics 21, 033004 (2019)
[2] P. Giannozzi, S. Baroni, N. Bonini, et al., Journal of Physics: Condensed Matter 21, 395502 (2009)
[3] R. C. Ehemann, P. S. Krstić, J. Dadras, P. R. C. Kent, and J. Jakowski, Nanoscale Research Letters 7:198 (2012)