PhD positions offers

The Atom Probe Tomography (APT), the laboratory's flagship technique, enables the 3D reconstruction of the chemical distribution of a nano-object, with spatial resolution close to the atomic scale, using field evaporation of ions from the surface. In laser-assisted APT, commonly used to study metals, insulators and semiconductors, evaporation is triggered by an ultrafast laser pulse in the near ultraviolet (UV) range [1-2]. The energy of the UV pulses is absorbed by the sample and its heating degrades the instrument's performance in terms of spatial and chemical resolution.

Remarkable progress has been made using sources in the terahertz (THz) range, which has enabled the analysis of metallic materials as well as ceramics and oxides [3-5]. In addition, it has been shown that the emission process assisted by THz pulses minimizes heating effects. When using single-cycle THz pulses, an important role is played by their polarity (or sign) and spectrum. With positive pulses, the thermal effects are reduced in the case of metals, but are clearly visible in the case of band-gap materials. On the other hand, all materials can be analyzed with negative THz pulses and the performances are similar to that of UV lasers or degraded, depending on the spectrum of the THz pulse used.

In this context, a PhD thesis is being proposed to study the evaporation processes involved in the use of THz pulses as a function of their polarity and spectrum. To this end, it will be necessary to:

- Analyze materials with different band gaps in SAT-THz, by varying the polarity and spectrum of the pulse.

- Develop the generation bench in order to spectrally control the THz pulse generated.

- Couple the results of the analyses with numerical simulations of the trajectories of the ions and electrons emitted by the THz pulse.

Contact:

Interested candidates should send the following documents:

- Detailed CV with academic background.

- Letter of motivation

- Transcripts and rankings from Master 1 and Master 2.

Contact : angela.vella@univ-rouen.fr

Teeth are particularly fascinating due to their remarkable properties and essential role in mastication. While most dental research focuses primarily on human or mammalian teeth, the diversity of dental tissues in animals provides valuable insights for biomaterials, biomineralization, and bio-inspired designs.
This project specifically investigates fish teeth, whose crowns are composed of enameloid—a material distinct from human enamel in both chemical composition and structure, yet remarkable for its mechanical properties. Additionally, certain fish species exhibit unique pigmentation, ranging from red and orange to green and blue, which remains largely unexplored in terms of both function and structure.
To analyze these tissues at an extremely fine scale, the project aims to advance the application of atom probe tomography (APT), a cutting-edge technique capable of mapping chemical composition in 3D with near-atomic resolution. The mechanical properties of fish teeth will also be examined at different hierarchical levels, integrating innovative in situtesting methods under specific conditions. This work will provide new insights into tooth formation, biomineralization processes, and innovative applications in dentistry as well as the design of bio-inspired implants.

Contact:
Interested candidates should submit the following documents:

• A detailed CV outlining their academic background
• A motivation letter
• Transcripts and rankings for Master 1 and Master 2

and send them to Philippe Pareige – philippe.pareige@univ-rouen.fr and Maïtena Dumont – maitena.dumont@univ-rouen.fr

Project description

The development of new light-emitting diodes (LEDs) based on innovative materials meets major technological, economic and environmental challenges. Current LEDs, although efficient, have limitations linked to the use of expensive and sometimes rare materials, the extraction of which can have a significant environmental impact. In addition, optimising LED performance, particularly in terms of energy efficiency, thermal stability, durability and colour rendering, requires ongoing exploration of new materials.

Nanomaterials offer unique optical and electronic properties, such as tunable luminescence, high quantum efficiency and the ability to cover a wide colour spectrum. These characteristics make it possible to meet growing needs in areas such as high-efficiency lighting, high-resolution displays and wearable technologies. In addition, the development of non-toxic and easily recyclable materials is part of a sustainability approach that is essential in the face of today's environmental challenges. The integration of these new materials into LEDs promises to improve their performance while reducing their ecological impact, contributing to a transition towards more environmentally-friendly technologies.

Problematic

The aim of this thesis project is to continue work on the white light emission of strontium vanadate complexes for the development of new LEDs, as part of the ANR LEDVAN project currently underway between the GPM in Rouen, CIMAP and CRISMAT in Caen. Recent work between these partners has highlighted the particularly interesting properties of these materials (CMOS-compatible crystal growth, optical and electrical properties, transparent and conductive oxide properties) for such developments.

However, very few studies have been carried out on these materials, and to date there is no literature that adequately describes the experimental observations, particularly on the growth mechanism. Our recent work has revealed a strong disparity in the nanostructures observed after processing, depending on the initial thickness of the thin film: ranging from the presence of nanometric islands to homogeneous films, via agglomerates of grains. The associated luminescence is partially correlated with the nanostructure obtained. It is therefore essential to understand the influence of processing parameters (thickness, annealing, etc.) in order to optimise luminescence (colour and intensity).

Profile required:

The candidate should hold a Master's degree in Physics, Materials Science or Nanosciences. The candidate should have knowledge of materials science and solid state physics, and a particular interest in experimentation. Knowledge of the optical properties of semiconductor and/or oxide materials would be highly appreciated.

Contact :

Interested candidates should send the following documents

- Detailed CV

- Letter of motivation

- Transcripts of marks from Licence 3, Master 1 and Master 2.

Etienne Talbot – etienne.talbot@univ-rouen.fr, 02.32.95.51.32

The objective of this thesis is to study trap phenomena in the latest generations of Gallium Nitride (GaN)-based High Electron Mobility Transistors (HEMTs). Various methods for characterizing trap behavior in GaN HEMTs exist, such as Deep Level Transient Spectroscopy (DLTS) for capacitance and current (C-DLTS and I-DLTS), Athermal Direct Current Transient Spectroscopy (A-DCTS), Deep Level Optical Spectroscopy (DLOS), Gate-Lag (GL) and Drain-Lag (DL) transient measurements, the study of transconductance frequency dispersion, S-parameter measurements, and low-frequency noise measurements. The temporal and thermal ranges explored by these techniques are sometimes different, highlighting the complementarity of these measurements.

The candidate must have training in electronics, with knowledge of RF power transistors. Knowledge in the field of materials (semiconductors, solid state physics) and physical simulation will be appreciated.

Contacts : Pascal Dherbécourt, 02 32 95 51 57. Niemat Moultif, 02 32 95 50 78.
Interested candidates should send a cover letter and their CV to : pascal.dherbecourt@univ-rouen.fr ; niemat.moultif0@univ-rouen.fr; mohamed.masmoudi@univ-rouen.fr .