Starting: from 10/2025 

Laboratory: Center for Nanosciences and Nanotechnologies (C2N)

Address: 10 Boulevard Thomas Gobert, 91120 Palaiseau, France

Supervisor(s): Amaury Delamarre – 01 70 27 04 80 

Send application to: amaury.delamarre@cnrs.fr

The Institute:

The Centre for Nanosciences and Nanotechnology (C2N) is a joint research unit between the CNRS and Université Paris-Saclay. The center develops research in the fields of material science, nanophotonics, nanoelectronics, and nanotechnologies, covering all the range from fundamental to applied sciences. The PhD thesis offered here will take place in the Sunlit Team, which develops innovative approaches for solar cells, aiming at high efficiencies, cost reduction and reliability of the photovoltaic devices.

Scientific project:

Solar cells made of III-V materials present the best efficiencies among currently available technologies, up to 46% under concentration. Nevertheless, their cost is significantly higher than mainstream silicon modules. The major part of this cost, about 80% to 90%, lies in the III-V substrates necessary for the growth of monocrystalline materials with sufficient quality.

We propose to explore a new strategy to reuse the substrate for several consecutive growths, in order to drastically reduce its cost contribution. The main goal is to modify the surface of the III-V substrate, so that the fabricated III-V layers can be easily detached, leaving a clean surface suitable for subsequent layer fabrication. A promising route for surface modification consists in depositing graphene layers on top of the substrate. The complete process is depicted in the figure below.

The objectives of the thesis project are twofold: (i) To define and develop the technological stages of the method, which include the manufacture and transfer of graphene, as well as the epitaxy itself (by molecular beam epitaxy). (ii) Clarify the nature of the physical interactions between the fabricated layers, the graphene, and the substrate. Several mechanisms may be involved, including Van der Waals interactions across the graphene layer, but also nucleation phenomena localized at graphene openings. The contribution of these phenomena needs to be quantified so that they can be manipulated to produce III-V thin films of sufficient quality for the production of high-efficiency solar cells. This would constitute a new tool for the growth of III-V materials, opening up a wealth of applications, such as photovoltaics (targeted in this project), but also photonics on silicon or flexible devices…

This work will take place at the Center for Nanoscience and Nanotechnologies (C2N) in the SUNLIT team. It includes several methods of fabrication (III-V by MBE, nano-fabrication clean room processing) and characterization (luminescence, SEM, TEM). Collaboration with high level scientists in specialized techniques are expected (XPS, STM). This environment gives the PhD candidate many opportunities to tackle this project challenge and gain experience.

Profile:

The ideal candidate will have a master degree in physics, engineering, material sciences or related. Previous experience in clean-room is desirable but not essential. The candidate must show good organization skills to fabricate the target materials, using methods implying numerous parameters, in a clean room environment. A proactive approach is expected. Collaborative work being at the core of the program, communication skills are required for team working as well as regular presentation of work progress in internal meetings and conferences.

Websites: https://sunlit-team.eu; https://www.c2n.universite-paris-saclay.fr