Internal structure of ferroelectric nanocrystals: coupling between local piezoresistance microscopy and optical measurements

Full description

In the framework of a collaboration between our laboratory and two other laboratories on the Saclay plateau (ENS Paris-Saclay/ LUMIN and CentraleSupelec/ SPMS), we have been interested in the study of possibly doped BaTiO3 dielectric nanoparticles. Indeed, the luminescence and frequency conversion properties (second harmonic generation – SHG) of these particles make them promising labels for applications such as optical imaging in biological environments, one example being the monitoring of intracellular transport within neuronal networks.

Following a recent study, coupling simulations and piezoresistance force microscopy, PFM , we have observed that BaTiO3 nanocrystals could exhibit quite a peculiar structure, with alternating “up” and “down” ferroelectric domains. These results raise the question of the origin of the non-linear optical response of second harmonic generation (SHG) of these nanocrystals. Indeed, the existence of domains oriented at 180° to each other should give rise to an absence of SHG following destructive interferences, which is not what is observed experimentally.

The aim of the internship will be to carry out more in-depth analyses correlating PFM and SHG so as to enable a more complete characterisation of the structure of these nanocrystals and a better understanding of their properties. To reach this objective, we will work with slightly larger crystals than those studied so far, so as not to be limited by the diffraction limit for optical measurements.

The host team is the Nanophotonics group of SPEC/LEPO (http://iramis.cea.fr/spec/LEPO/). For the needs of its research, the group has developed an important know-how in the coupling of optical measurements with local probe microscopies, AFM in particular. The team has several experimental benches of this type that will be taken into profit during the internship. Depending on the samples that will be considered, AFM / PFM and SHG measurements will be carried out either simultaneously or sequentially on the same objects…

The role of the student will range from the sample preparation, to their optical / PFM thorough characterization. He/She will also participate in the interpretation of the results that will be obtained.

Location

France

Internship conditions

• Internship duration: 4 months
• Level of study: Bac+4/5
• Training: Ingenieur/Master
• Continuation in PhD thesis: No
• Application deadline: 1 février 2024

• Useful methods and technics:
• Sample preparation (drop-casting, spin-coating)
• SEM characterization
• Local probe measurements (AFM electrical modes)
• Optical measurements (frequency conversion, in particular 2nd harmonic generation – SHG)

Links

Supervisor

Céline FIORINI-DEBUISSCHERT
Phone: 06 60 49 17 35
Email :

Head of the laboratory SPEC / LEPO

Ludovic DOUILLARD
Phone: 01 69 08 36 26