Covalent 2D organic nanostructures by optically controlled cross-linking of molecular self-assemblies

Full description

Context:

The interaction between a material and its environment occurs primarily at its surface. Producing high-quality surfaces is therefore an important scientific goal. Nano-structuring this surface makes interactions more selective and allows for new optoelectronic properties. One promising approach is the self-assembly of molecules on a crystalline substrate. This method is flexible and allows to obtain a wide variety of organized 2D supramolecular networks with promising properties for optoelectronics and sensing. However, these assemblies are based on non-covalent bonds, making them fragile and thermally unstable.

To strengthen these networks, our approach is to bond molecules together on the surface, thus creating a covalent 2D network. This covalent network formation can be achieved by heating under ultra-high vacuum, which can however induce defects in the surface. An interesting alternative is to to trigger the cross-linking of the network with optical excitation, which allows for new control parameters: wavelength and polarization of light. We propose to create such molecular assemblies under ambient or ultra-high vacuum conditions and characterize them using optics and scanning probe microscopies.

Objectives:

• Preparation and characterization of molecular assemblies, in air or at the liquid–solid interface and in ultra-high vacuum condition, using optical and scanning probe microscopies (scanning tunneling microscopy (STM), atomic force microscopy (AFM)).
• Monitor their evolution under light excitation to demonstrate localized photochemical cross-linking under ambient conditions.

The project will thus establish a proof of principle of light-induced nanoscale chemistry at the wavelength scale, combining optics and scanning probe techniques.

Environment

We are looking for a motivated candidate with a strong academic background in chemistry or physics, willing to continue for a PhD thesis after the internship. The thesis is fully funded by an ANR grant. A visit of the lab and the discussion of the project to adapt to the candidate’s interest is possible.

Location

CEA Saclay, Site de l’Orme des merisiers (91) Essonne, France

Internship conditions

• Internship duration: 6 months
• Level of study: Bac+5
• Training: Master 2
• Continuation in PhD thesis: Yes
• Application deadline: 1 janvier 2027

Useful methods and technics:

• Experimental techniques:
• Scanning Tunnelling Microscopy
• Atomic Force Microscopy
• Optical spectroscopy
• Sample preparation (spin-coating, Langmuir-Blodgett)

Supervisor

Nicolas Fabre
Phone: 0169084720
Email :