Geoffroy Prévot
Geoffroy Prévot is Director of Research at the CNRS and Deputy Director of the Paris Institute of NanoSciences at Sorbonne University. His research focuses on the growth, structure and reactivity of low-dimensional systems: surfaces, thin films and epitaxial nanoparticles. He is a specialist in scanning tunneling microscopy and grazing incidence X-ray diffraction techniques. As part of his research, he is developing tools and methods for real-time monitoring of surfaces under environmental conditions using tunneling microscopy (e.g., during growth or exposure to reactive gases). He collaborates with the SIXS surface diffraction beamline at the SOLEIL synchrotron, for which he develops tools for analyzing surface X-ray diffraction data.
Abstract
Atomic structure of epitaxial 2D materials elucidated by Surface X-ray diffraction
Since the experimental discovery of graphene, thousands of 2D materials have been identified by numerical simulations. However, only a small part of them has been synthesized, most often by exfoliation of the bulk material. Conversely, the epitaxial growth of 2D materials can lead to the formation of new structures differing from those of their bulk counterparts. This is for example the case of silicene, germanene or stanene, which have an electronic structure similar to the one of graphene, but do not form lamellar materials.
For these novel epitaxial 2D monolayers, the knowledge of their atomic structure is a key point for the understanding of their properties (electronic, optical, mechanical, etc.). For this purpose, surface X-ray diffraction is by far the most quantitative method. Indeed, the diffracted intensities measured in reciprocal space are proportional to the squared modulus of the Fourier transform of the electronic density.
In this talk, I will present the classical methods used to retrieve the atomic positions from the diffraction measurements (such as structure refinement with chi-square minimization or analysis of the Patterson map), the recent developments achieved with phase retrieval algorithms, and some perspectives. Examples will be taken from epitaxial silicene and germanene layers recently synthesized on metal substrates, and measured on the SixS beamline of Soleil synchrotron.1–7
1. Curcella, A. et al. Physical Review B 94, 165438 (2016) doi:10.1103/PhysRevB.94.165438
2. Prévot, G. et al. Physical Review Letters 117, 276102 (2016) doi:10.1103/PhysRevLett.117.276102
3. Curcella, A. et al. Physical Review B 99, 205411 (2019) doi:10.1103/PhysRevB.99.205411
4. Zhang, K. et al. Physical Review B 104, 155403 (2021) doi:https://doi.org/10.1103/PhysRevB.104.155403
5. Leoni, T. et al. J. Phys. Chem. C 125, 17906–17917 (2021) doi:10.1021/acs.jpcc.1c02088
6. Zhang, K. et al. Phys. Rev. B 106, 045412 (2022) doi:10.1103/PhysRevB.106.045412
7. Zhang, K. et al. ACS Nano 17, 15687–15695 (2023) doi:10.1021/acsnano.3c02821
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