Transition metal oxides exhibit intricate electronic correlations that give rise to phenomena such as superconductivity, magnetism, Mott transitions, and multiferroicity. Achieving precise control over these synthetic quantum materials requires a collaborative synergy between materials design and advanced experimental characterization techniques.
Understanding the atomic-scale interface properties in heterostructures is crucial for engineering oxide-based electronic devices. Of particular interest are novel phenomena, such as the emergence of a two-dimensional electron gas (2DEG) at these interfaces.
Structural and electrostatic interactions between the insulating and metallic regions of the ferroelectric material lead to the emergence of switchable dipoles within the metallic component, resulting in the creation of a unique ferroelectric 2DEG. To explore these interfaces with sub-angstrom resolution, we employ a powerful combination of Scanning Transmission Electron Microscopy (STEM) coupled with Electron Energy Loss Spectroscopy (STEM-EELS) and four-dimensional scanning transmission electron microscopy (4D-STEM). This approach enables us to observe directly the interfacial atomic structure(classic HAADF imaging), and measure elemental composition, charge re-distribution at the interface (EELS), as well as electron polarization and electric field biasing at the interface (4D-STEM)1,2.
The primary goal of this work is to demonstrate the development of a 2DEG induced by polarization. We will use a LaAlO3/EuTiO3/Ca-SrTiO3 heterostructure as the specimen3, which exhibits a 2DEG showcasing coexisting coupled ferroelectricity, magnetism, and metallic behavior.
During the internship, the participant will actively engage in data acquisition using the team’s STEM microscopes (https://equipes2.lps.u-psud.fr/en/scanning-transmission-electron-microscopes/). Subsequently, they will analyse the data, including hyperspectral EELS and 4D-STEM images, using existing software tools.
Reference:
[1] Npj Quantum Materials (2021) 6:88.
[2] Adv. Mater. Interfaces (2023), 10, 2202165.
[3] Nature Physics, (2019), 823–829.
Language: Python
Duration: March to July (flexible dates, possibility of extending to August).
Work from home possible 1 day/week
Tuition: €591.51/month
Access to CESFO restaurant at a student rate of €3.81 (Bât 598); rest room with fridge and microwave
Contact Xiaoyan LI (xiaoyan.li@universite-paris-saclay.fr) and Nathalie Brun (nathalie.brun@universite-paris-saclay.fr) for more details.