Open master internship + PhD position at the CELIA, Bordeaux, France

Non-equilibrium Chalcogenide Materials: From Fundamental Physics toTechnological Applications

Chalcogenide materials are alloys incorporating at least one element— Sulfur (S), Selenium (Se), or Germanium (Ge). These elements form the bedrock of groundbreaking concepts in microelectronics and microtechnologies, such as spintronics, thermoelectricity, infrared optics, and the development of non-volatile and neuromorphic memory components [1,2] (e.g., PCM/Phase-Change Memory, OTS/Ovonic Threshold Switching devices, ONL/Nonlinear Optics, TE/ThermoElectrics, FESO/FerroElectric Spin-Orbit devices). The operation of these materials relies, in part, on non-equilibrium physics induced by electronic excitation resulting from the application of a static electric field in real devices, which can be mimicked by an intense femtosecond laser pulse [3].

This internship seeks to simulate the impact of electronic excitation induced by an intense electric field or an optical laser pulse [3] on the atomic arrangement of these materials with femtosecond (fs) precision. Ab-initio simulations, utilizing a cutting-edge method developed at the University of Liège, will be coupled with a Time-Dependent Schrödinger Equation (TDSE) code implemented at CELIA. The materials of interest will be those crafted in the cleanroom at CEA-LETI, integral to industrial applications. The study will focus specifically on germanium selenide (GeSe) glasses and the ferroelectric phase of crystalline germanium telluride (GeTe).

-Regarding GeSe, the study will delve into investigating non-equilibrium phases and deducing the effects of this excitation on the electronic structure, coupling experimental results with the VASP simulation code.

- For ferroelectric GeTe, the aim is to scrutinize the efficiency of second harmonic generation and its application as a structural probe. This study will be executed using a TDSE approach that encompasses spin dynamics.

This work's objective is to anticipate the electronic and optical responses of different chalcogenide materials on femtosecond timescales under extreme field conditions. This will unravel the fundamental physical mechanisms connecting electronic excitation and atomic structure in these alloys, paving the way for design principles to optimize the performance of these materials in the future.

The internship will transpire at the CELIA laboratory in Bordeaux, closely collaborating with the "Chalcogenide Materials" group at CEA-LETI in Grenoble and theorists from the University of Liège. This internship may potentially segue into a doctoral thesis on the same subject, with secured funding, to be conducted at LETI in Grenoble, maintaining a tight-knit collaboration between CELIA/LETI/Univ Liège.

Skills required:

- Master's degree (Master 2) in physics/chemistry, ideally specialized in solid-state/materials.

- Programming skills, preferably in Python/Fortran.

[1] A. Piarristeguy, P. Noé, et F. Hippert, « Verres de chalcogénures pour le stockage de l’information », Reflets phys., no 74, p. 58-63, déc. 2022, doi: 10.1051/refdp/202274058.

[2] Noé et al.« Toward ultimate nonvolatile resistive memories: The mechanism behind ovonic threshold switching revealed ». Science Advance 6 : eaay2830 (2020)

[3] Martinez et al. «Sub-Picosecond Non-Equilibrium States in the Amorphous Phase of GeTe Phase-Change Material Thin Films. » Adv. Mater. 33, 2102721 (2021)

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Centre Lasers Intenses et Applications - UMR 5107 - UB/CNRS/CEA
43 rue Pierre Noailles – Talence - France