Description du sujet de thèse

Title: Quantum Nanodiamonds with Group-IV Color Centers for Sensing in Extreme Conditions
Keywords: quantum technologies, nanodiamonds, color centers, CVD synthesis, matter, optics, high-pressure physics.
Scientific description
Diamond is a remarkable material for various technological applications. Its compact and regular crystalline structure enables its use in diverse fields such as particle sensors and power electronics [1]. With recent advances in diamond synthesis techniques, new opportunities have emerged for quantum-scale applications, including in high-pressure and biomedical physics. This thesis focuses on the synthesis of diamond nanoparticles via chemical vapor deposition (CVD), incorporating Group-IV color centers (so-called G4V centers, such as silicon-vacancy (SiV), germanium-vacancy (GeV), tin-vacancy (SnV), etc.). A G4V center is a point defect in the diamond lattice, consisting of a Group-IV atom (e.g., Si) and two adjacent vacancies [2]. This defect introduces energy levels into the diamond bandgap that behave similarly to atomic energy levels. When subject to external perturbations (e.g., pressure, temperature), these levels shift, enabling the G4V center to function as a highly localized sensor. In particular, G4V centers exhibit highly concentrated luminescence in the zero-phonon line (ZPL), accounting for approximately 80% of the total emission even at room temperature, which makes them excellent candidates as single-photon sources. From a crystallographic perspective, the Group-IV atom relaxes symmetrically between two adjacent lattice vacancies, forming an inversion-symmetric complex. This structural symmetry ensures exceptional stability and performance under extreme conditions of temperature, pressure, and magnetic field.
In our recent work, we have successfully developed a protocol for synthesising CVD nanodiamonds containing SiV and GeV centres, and demonstrated their first use as high-pressure and stress sensors [3, 4]. These results have also opened up numerous areas of research that remain to be explored, which is the objective of this doctoral thesis.
This thesis, the core of the NanoG4V project, is structured around three main objectives:
1. Synthesize high-quality, quantum-grade CVD nanodiamonds containing G4V color centers with stable and highly emissive ZPLs, while also investigating the plasma environment, through both simulations and experiments, to understand particle formation and defect incorporation mechanisms.
2. Optimize the optical properties of G4V-NDs via original post-synthesis treatments, with in situ testing at the SOLEIL synchrotron to enhance their quantum performance.
3. Demonstrate proof-of-concept sensing, including: (i) Quantum sensing at pressures exceeding 100 GPa for extreme condition experiments, (ii) Quantum magnetometry under Tesla-range magnetic fields.
References
[1] M. De Feudis, PhD Thesis, University of Salento (Italy) and University of Sorbonne Paris Nord (France), 2018.
[2] C. Becher, et al., Materials for Quantum Technology 3 (1) 2023, p. 012501.
[3] M. De Feudis, et al., Advanced Materials Interfaces 7 (2) 2019, 1901408.
[4] B. Vindolet, et al., Physical Review B 106 (21) 2022, p. 214109.
Candidate Profile
The ideal candidate holds a Master's degree (or equivalent) in physics, materials science, nanoscience, or a closely related field, and demonstrates a strong interest in experimental research at the interface of quantum technologies and materials synthesis. Dynamism and determination are essential for success in this research.
Techniques and Methods
The project will involve a multidisciplinary approach combining chemical vapor deposition (CVD) of nanodiamonds, plasma diagnostics and simulation, structural and optical characterization of color centers (e.g., photoluminescence, Raman spectroscopy, electron microscopy), and advanced high-pressure techniques. Experience with vacuum systems, lasers, spectroscopy, or numerical modeling (e.g., plasma or molecular simulations) will be considered an asset. The candidate will have the opportunity to work in a dynamic international environment and perform experiments at large-scale research facilities, including the SOLEIL synchrotron.
Contact: Mary De Feudis, Associate Professor and PI of the NanoG4V project
mary.de.feudis@chimieparistech.psl.eu
PhD Location
The PhD will be based at the Institut de Recherche de Chimie Paris (IRCP), Chimie ParisTech, 75005 Paris. The student will also conduct research in NanoG4V project partner laboratories:
• LSPM (Université Sorbonne Paris Nord, Villetaneuse) with Fabien Bénédic and Jocelyn Achard, diamond synthesis platform managers.
• LuMIn (ENS Paris-Saclay, Gif-sur-Yvette) with Jean-François Roch and Marie-Pierre Adam, for high-pressure sensing experiments platform managers.
Duration: 36 months. Expected start: October 2025.
Funding: ANR JCJC “NanoG4V” : ANR-24-CE51-7558
Expected Outcomes
By the end of the PhD, the candidate is expected to:
• Acquire solid expertise in the synthesis and advanced characterization of quantum-grade nanodiamonds containing Group-IV color centers.
• Establish synthesis post-treatment strategies for improving quantum color centers properties.
• Produce proof-of-concept demonstrations of nanodiamond-based quantum sensors under extreme physical conditions.
• Present research results at international conferences and publish in high-impact scientific journals in the fields of nanomaterials, quantum sensing, and applied physics.

Contexte de travail

During the three-year PhD program, the student will be supervised by Mary De Feudis, PI of the NanoG4V project, and co-supervised by colleagues from the NanoG4V group. The student will also be supported by other young researchers from the NanoG4V team, as well as colleagues from IRCP team (CQSD-MPOE) such as Philippe Goldner. An added value of this PhD lies in the established collaborations with LSPM and LuMIn, enabling the student to gain hands-on experience in plasma synthesis and high-pressure physics, alongside leading experts such as Fabien Bénédic, Jocelyn Achard, Jean-François Roch and Marie-Pierre Adam. All the equipment needed to carry out the experiment is already operational.

Contraintes et risques

Low chemical risks, as particles are confined in liquid solutions. Low electrical risks: students are trained in the use of plasma sources and other electrical equipment.