Missions

Electron energy-loss spectroscopy (EELS) in the aberration-corrected scanning transmission electron microscope (STEM) is a powerful tool to obtain chemical information at high spatial resolution. Elemental maps at atomic resolution have become routinely accessible to indicate which element is where, however much more information on the local electronic structure is accessible from the spectral features of a given core-level excitation edge. The spectral fine structures (energy-loss near-edge structures - ELNES) reflect the local electronic structure and may inform on the geometry of the atomic site, chemical bonding, charge transfer, etc. For instance, interpreting ELNES maps in terms of unoccupied electronic orbitals has recently received renewed interest, using core-level excitation in EELS. Nevertheless, the reliable interpretation of ELNES variations often requires simulating the signal, and this is even more prominent at crystal discontinuities like defects or interfaces.
In this project, experimental ELNES data have been obtained at high-spatial resolution on various interfaces of interest (e.g. graphene/ceramic, perovskite/perovskite). Core-level excitation spectra at interfaces and defects, for which fine-structure variations are observed experimentally from one atomic plane to the next, must be calculated on a case-by-case basis to enable their interpretation. The mission of the candidate will be to lead the tasks of calculating core-level EELS spectra of atomic species located at (or near) crystalline interfaces of interest.

Activités

- Principal task: simulating EELS spectra (e.g. K edges of light elements) using quantum-mechanical atomistic calculations to provide a robust framework for interpreting spatially resolved ELNES variations. The simulations will be performed using established DFT codes or multiple scattering codes (like WIEN2k or FEFF). Approaches beyond the one-electron approximation could also be considered in collaboration with other research groups. Access to high-end computing resources necessary to carry out the work will be provided on the Lyon campus.
- Principal task: communicate results in peer-reviewed articles.
- Principal task: communicate results effectively at conferences/workshops.
- Secondary task (optional): take part in EELS experiments.

Compétences

• Proficiency in atomistic simulations (DFT or multiple scattering) and strong experience in simulating spectroscopy data such as EELS or XAS.
• Knowledge of electron-matter interactions.
• Excellent written and verbal skills in English
• The candidate is expected to be conscientious, creative and initiative-driven, show autonomy, scientific rigor, and motivation for academic research.

Contexte de travail

MATEIS is a Materials Science and Engineering laboratory with a multidisciplinary approach including Physics, Chemistry and Mechanics. It is composed of about 180 people, and is organized in 6 different groups. The three classes of materials are investigated (metals, ceramics, polymers and their composites) integrating volume, surfaces and interfaces. MATEIS is focused on relations between Process-Microstructure-Properties, with an experimental and/or modelling approach. MATEIS focuses particularly on advanced processing methods, microstructural evaluation (often in situ and in 3D), mechanical and multi-functional properties in relation to architectures, as well as modelling at different scales. MATEIS is involved on societal issues ('Materials for'): health, energy, environment, transport, building applications.

The general objective of the microscopy group is to understand the multiscale structure of materials, in view to better understanding the relations with their properties of use. Development of new characterization techniques in scanning and transmission electron microscopy is presently focused on in situ and operando techniques on the different microscopes of the CLyM (Lyon Saint-Etienne Microscopy Center). The microscopy group is composed of 3 professors, 4 associate professors, 1 researcher, PhD students, postdoctorate fellows and technical/administrative staff.