Offres de Post-doctorat
Post-doctoral position Atom Probe Tomography driven by ultrashort pulses in the extreme ultraviolet (EUV)
Spatially coherent sources of high-energy extreme-ultraviolet (EUV) photons and the tight focusing associated to the EUV beams are required for various scientific and industrial applications such as nanoscale imaging by atom probe tomography. The atom probe tomography (APT) is an advanced characterization method with very high spatial resolution that allows performing analytical imaging of materials in three dimensions at the atomic scale [Blavette1993, Gault2006]. Remarkable advances in the analysis of insulating materials were only achieved using UV laser pulses (around 340-400 nm) thanks to their high photon energy, thus paving the way for APT exploitation in new areas such as geophysics and biology. The use of EUV sources with photon energy up to 20 eV will allow the analysis of ultrawide band gap materials and will also improve the chemical composition measurements.
This project aims first to build a EUV photons source based on High Harmonic Generation (HHG) in large bandgap material (amorphous silica) using a long wavelength (mid-infrared) few-cycle (sub-30 fs) laser. Indeed, HHG in amorphous silica has already enabled the production of high photon flux at energies up to 25 eV [You2017].
The second objective will concern the coupling of the EUV source to an APT chamber to analyse wide band-gap materials in order to explore the evaporation process induced by such high energy photons and thus evaluate their potential for APT’ performances improvement [Vella2013].
The generation of EUV light in large band-gap materials and its application to APT are in the focus of the ANR project (Flex-UV) that will be conducted in collaboration between the GPM group (The University of Rouen, gpm.univ-rouen.fr, the laboratory LOA (École Polytechnique https://loa.ensta- paris.fr/the-laboratory/organization/) and the laboratory Xlim (The University of Limoges : https://www.xlim.fr/)
Post-doctoral position (starting from October/November 2022)
The work consists to develop an optical bench to generate EUV pulses starting from the post- compression of sub-picosecond pulses delivered by a fiber laser and their focusing on oxide materials. After characterization, the EUV light will be coupled to the Atom Probe Tomography chamber, assuring the focusing of EUV wavelengths on the nanometric sample.
The work will be aimed at the activation and optimization of the ATP results, such as time-of- flight spectra, and the study of photo-ionization process.
The successful candidate can be specialized in physics with particular knowledge in optics, non-linear optics and laser-matter interactions. Previous experience in laser development or high harmonic generation will be highly appreciated.
Contact : Pr Angela Vella
Groupe de Physique des Matériaux, 76801 SAINT ETIENNE DU ROUVRAY CEDEX FRANCE
Phone: (33) (0)2 3295 5168
In the framework of a new project (Fusion SATMET), GPM has recently acquired a new STEM equipped with a time resolved direct detection camera, electron precession and advanced softwares allowing for orientation mapping. Preliminary work has allowed the design and fabrication of original TEM holders that allow to reproduce the condition of APT in STEM, i.e. application of a high voltage (DC + pulsing) to a sharp needle at cryogenic temperature. Beyond the coupling with APT detection in STEM, a main axis of the project is to take advantage of 4D STEM methodologies to extract a maximum of information such as: i) the electric field mapping in and around the polarised specimens; ii) evolution of electric field distribution during the sequence of field evaporation of specimens; iii) the mapping of crystal defects (e.g. grain boundaries, dislocations).
We are now seeking a post-doctoral fellow that will rapidly be able to produce original results that shall be published from the first year of the fellowship. Candidates must hold a PhD in materials sciences. A strong background in transmission electron microscopy is highly recommended. Skills in coding will be appreciated (e.g. python, MatLab, c++). Previous experience with atom probe tomography and/or specimen preparation in FIB SEM is not mandatory but might be considered interesting.
The duration of the post-doctoral fellowship is 1 year (+1 renewable year possible), starting autumn 2022 or earlier. This post-doctoral fellowship is granted by the European Union (ERDF) and Normandy Regional Council in the framework of RIN Tremplin Fusion SATMET.
Interested candidates should send a CV, a letter of motivation and the names of 2-3 references to firstname.lastname@example.org
Subject of the postdoc :
The tomographic atom probe is a quantitative nano-analysis tool that allows us to image in three dimensions a small volume of a metal sample at the atomic scale. This instrument was developed in the lab 30 years ago. It is now an indispensable tool in materials science whether in the fields of micro-electronics (development of integrated system, physical cause analysis of their failures…), energy and metal materials industrial purposes (automotive, aeronautics, nuclear industry ...). This instrument is commercialized by CAMECA (> 100 machines installed worldwide). The basic principle of this technique is the field evaporation of atoms of a sample, and detection of these emitted particles in the form of ions by a high-performance detector. The detector converts the impact of an ion into a coordinate (X, Y) and flight time. Since 1993, several generations of detector for atom probe has been developed by the instrumentation team, with each generation a technological leap that allowed improving significantly the performances of the instrument and the increase in dataset sizes (up to 109 atoms). Extracting useful information from probed dataset is the ultimate goal of this nano-analysing tool.
This post-doctoral research project (collaboration with CAMECA) proposes
1/ Development of new fast and efficient data mining algorithms dedicated to APT datasets.
2/Integration of algorithms in the CAMECA opened AP Suite extension Infrastructure. For this aim, frequent discussion with CAMECA lab is necessary.
The candidate (man or woman) must have a Phd in physics, electronics, instrumentation or related disciplines and a keen interest in academic research in an industrial development environment. A possible experience (projects, internships, etc ...) in the field of scientific instrumentation, software development in instrumentation would be appreciated. The candidate will be supervised by specialists in scientific instrumentation, physics, and materials science. The candidate must have an excellent level in English (frequent meetings with our industrial partner).
Deadline for application : July, 10th 2022 (send CV+ motivation letter)