Description du sujet de thèse

The CRHEA laboratory (CNRS / Université Côte d'Azur – Valbonne (06)) is looking for a candidate for a PhD thesis as part of a collaborative project with the LAGRANGE laboratory (Université de la Côte d'Azur / Observatoire de la Côte d'Azur / CNRS - Nice (06)), funded by the Mission pour les Initiatives Transverses et Interdisciplinaires (MITI). The project aims to develop analytical approaches based on materials science techniques in order to bring new perspectives to the field of cosmochemistry. For several years, these two laboratories have been collaborating on the analysis of extraterrestrial materials. The original approach is to apply cathodoluminescence (CL) - a technique commonly used to characterize semiconductors - to the study of so-called primitive extraterrestrial materials. Indeed, these provide essential clues about the formation and evolution mechanisms that occurred during the formation of our solar system, 4.567 Ma ago [1]. The value of this collaboration has been confirmed by the wealth of information obtained through cathodoluminescence on numerous samples, whether they are meteorites or those brought back by recent NASA or JAXA space missions [2-4].

Today, the ability of changing the scale of analysis to examine these objects at nanometric or even atomic resolutions has become essential for a better understanding of the mechanisms at work in order to obtain precise information on the formation conditions of these extraterrestrial materials.

In this context, the aim of this project is to propose and develop a multi-scale approach aimed at documenting the formation history of these objects. The originality of the project lies in the implementation of a multi-scale approach (from micrometer to nanometer) and correlative analysis of samples from various sources (samples from the Bennu and Ryugu asteroids, carbonaceous meteorites, synthetic samples), by combining scanning electron microscopy and cathodoluminescence (SEM-CL) with advanced transmission electron microscopy (TEM) techniques such as high-resolution imaging (HR-STEM) and electron diffraction (ED), available on the CRHEA's latest-generation microscope, as well as analysis by X-ray spectroscopy (STEM-EDX). The thesis plan proposed in this work project is divided in three points: i) carrying out morphological and spectral analyses using scanning electron microscopy coupled to cathodoluminescence (SEM-CL) ii) developing a methodology for identifying areas with grains containing primitive phases, which will allow to elaborate very fine slides/sections required for an in-depth study of the grains on a nanometric or even atomic scale, using transmission electron microscopy iii) structural and microstructural characterization using advanced electron microscopy techniques of the selected grains and validation of the characterization protocols.

Contexte de travail

Location: Laboratoire CRHEA (Centre de Recherche sur l'HétéroEpitaxie et ses Applications), Rue Bernard Grégory, 06560 Valbonne, France. www.crhea.cnrs.fr
Full-time equivalent job.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

This subject is addressed at two possible candidate profiles: Master's degree in Materials Physics or Master's degree in Mineralogy/Geology. Regarding the multidisciplinary nature of the subject, the chosen candidate must be highly motivated and interested in deepening related knowledge not initially covered during his/her initial training (Mineralogy for a Materials Science profile, or Luminescence and Structures for a Mineralogy/Geology profile).