Postdoctoral fellow (M/F): study of the tunability under electric field of the thermal conductivity of ferroelectric materials by thermoreflectance

13 Feb 2024
Job Information

Organisation/Company

CNRS

Department

Groupe de Recherche En Matériaux, Microélectronique, Acoustique, Nanotechnologies

Research Field

Physics

Researcher Profile

First Stage Researcher (R1)

Country

France

Application Deadline

4 Mar 2024 - 23:59 (UTC)

Type of Contract

Temporary

Job Status

Full-time

Hours Per Week

35

Offer Starting Date

3 Jun 2024

Is the job funded through the EU Research Framework Programme?

HE / ERC

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

The main mission of the postdoctoral fellow will be to study the field tunability of the thermal conductivity of ferroelectric materials. The measurement of thermal conductivity will be done by thermoreflectance as a function of temperature and electric field. These measurements will be carried out both with a commercial thermoreflectance device from Netzsch at GREMAN (Tours) and laboratory thermoreflectance benches developed at LOMA (Bordeaux).

Context: the development of thermal switches to control heat flows [1] would significantly improve the efficiency of thermoelectric devices and solid refrigeration systems. As part of this project, the postdoctoral researcher will explore an original mechanism based on the interaction between phonons and spontaneous planar defects in ferroelectric materials, to design thermal switches. Ferroelectric materials spontaneously exhibit regions of uniform polarization called domains. They are separated by planar defects called domain walls [2]. The polarizations can be switched, and therefore the number of domains and their orientations controlled, by applying a voltage. Domain walls have complex deformation profiles and interact with phonons as defects do [3]. Thus, as the density of domain walls increases, the number of collisions between domain walls and phonons increases and the thermal conductivity is reduced. Controlling the density of domain walls via the application of an electric field would therefore ultimately make it possible to develop a compact and efficient thermal switch over a wide temperature range.

[1] Wong et al. A review of state-of-the-art thermal diodes and their potential applications. Int. J. Heat Mass Transfer. 164, 120607 (2021) [2] Nataf et al. Domain-wall engineering and topological defects in ferroelectric and ferroelastic materials. Nat. Rev. Phys. 2, 634–648 (2020) [3] Limelette et al. Influence of ferroelastic domain walls on thermal conductivity. Phys. Rev. B 108, 144104 (2023).

The project will focus on the study of heat transport at small scales of time and space in ferroelectric materials in the form of single crystals, thin films, and superlattices, which will be produced by other members of the team or obtained via already existing collaborations. The domain structure of these materials will be controlled in-operando by applied voltages. Thermal conductivity will be measured by thermoreflectance as a function of temperature and applied voltage.

The postdoctoral researcher will work in two laboratories: GREMAN (UMR CNRS 7347) in Tours and LOMA (UMR CNRS 5798) in Bordeaux. GREMAN has strong expertise in ferroelectric oxides (from their growth to their integration into devices, including their complete characterization) and in the measurement and modelling of thermal transport. LOMA activities aim to explore and characterize the properties of matter from a fundamental and applied point of view. The laboratory develops techniques based on the use of atomic force microscopes and femtosecond pulse lasers to characterize materials, and in particular energy transport at small scales.

This project is part of the ERC Starting Grant “DYNAMHEAT”.

Requirements

Research Field

Physics

Education Level

PhD or equivalent

Languages

FRENCH

Level

Basic

Research Field

Physics

Years of Research Experience

None

Additional Information
Eligibility criteria

The candidate must hold a doctorate in physics or materials science, and have experience in thermoreflectance measurements and/or with pulsed lasers. Knowledge of ferroelectric materials would be appreciated. Good communication and writing skills, including English, are required.

Website for additional job details

https://emploi.cnrs.fr/Offres/CDD/UMR7347-GUINAT-003/Default.aspx

Work Location(s)

Number of offers available

1

Company/Institute

Groupe de Recherche En Matériaux, Microélectronique, Acoustique, Nanotechnologies

Country

France

City

TOURS

Geofield

Where to apply

Website

https://emploi.cnrs.fr/Candidat/Offre/UMR7347-GUINAT-003/Candidater.aspx

Contact

City

TOURS

STATUS: EXPIRED