This thesis project aims to develop ultra-compact, high-resolution, and large-range electrostatic field sensors based on a novel concept, for which patents are pending. This original sensor is obtained by combining an encapsulated graphene field-effect transistor (GFET) and a vibrating MEMS. It should achieve performances similar to field mills (resolution < 1 V/m, measuring range of 1 MV/m) with significant gains in size, weight, cost, and consumption. From this point of view, this sensor aims for better performances than existing technologies, whether traditional (field mill (Buguet et al., 2021)) or miniaturized (MEMS (Riehl et al., 2003), p-MEMS (Xue et al., 2020)). It addresses a strong application need for minimally invasive instrumentation of characterization benches in space environments (e.g., ONERA's JONAS bench) and monitoring of the electrostatic charging of satellites in flight. Potential applications outside the space domain are also numerous (lightning risk detection/assessment, measurement of electrostatic charges on in-flight vehicles, particularly for defense).

The initial work conducted at ONERA and further developed as part of Jules MAISTRET's ONERA/CNES thesis (2023-2026) has provided proof of concept using a simplified version of the sensor, for which the MEMS is absent and its effect on the transistor is generated by external instruments (Maistret &amp; Lavenus, 2024). The experimentally validated detection mechanism has made it possible to build a performance model, determine the influence of various material and geometric parameters, and identify several bottlenecks. The thesis focused in particular on three key aspects: (i) the encapsulation of graphene, a crystal of monoatomic thickness, by alumina deposited by ALD (Atomic Layer Deposition – collaboration with the Physics Laboratory of the ENS) in order to make the graphene insensitive to the adsorption/desorption of molecules from its environment and thus stabilize the sensor, (ii) the control and measurement electronics associated with the transistor and (iii) the MEMS/transistor assembly.

The new thesis proposed here is a continuation of Jules Maistret's thesis. The objective of this new thesis will be to produce a first characterized prototype of the sensor and its electronics. The work will be divided into two main tasks:

- I) Improving the reliability of the graphene encapsulation process using alumina. The devices manufactured in Jules Maistret's thesis exhibit variability in transistor characteristics, whether in terms of doping, mobility, trap density contributing to hysteresis phenomena, or contact resistance. The work will therefore focus on optimizing the manufacturing process. The conditions for alumina deposition and contaminant desorption/recrystallization annealing will be investigated. Semi-dry graphene transfer will be considered, as an alternative to wet transfer, to reduce the density of adsorbates on graphene, which can generate traps. This work will be carried out in the clean rooms at ONERA and LP-ENS. The optical and electrical characterizations of the transistors will be conducted at ONERA, using a dedicated instrumentation bench.

- II) Study of the MEMS/transistor assembly. This will particularly involve better understanding the MEMS/transistor coupling from an electrical and mechanical perspective. This study will be carried out in a vacuum probe station that combines electrical measurements of the MEMS and optical measurements using displacement interferometry.

References :

Buguet, M., Lalande, P., Laroche, P., Blanchet, P., Bouchard, A., &amp; Chazottes, A. (2021). Thundercloud electrostatic field measurements during the inflight exaedre campaign and during lightning strike to the aircraft. Atmosphere, 12(12), 1645. https://doi.org/10.3390/atmos12121645

Maistret, J., &amp; Lavenus, P. (2024). Understanding Electrostatic Sensing with Graphene: A Miniature and Versatile Alternative to Standard Technologies. Proceedings of IEEE Sensors, 92320. https://doi.org/10.1109/SENSORS60989.2024.10784967

Riehl, P. S., Scott, K. L., Muller, R. S., Howe, R. T., &amp; Yasaitis, J. A. (2003). Electrostatic charge and field sensors based on micromechanical resonators. Journal of Microelectromechanical Systems, 12(5), 577–589. https://doi.org/10.1109/JMEMS.2003.818066

Xue, F., Hu, J., Guo, Y., Han, G., Ouyang, Y., Wang, S. X., &amp; He, J. (2020). Piezoelectric-piezoresistive coupling MEMS sensors for measurement of electric fields of broad bandwidth and large dynamic range. IEEE Transactions on Industrial Electronics, 67(1), 551–559. https://doi.org/10.1109/TIE.2019.2893837

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For more Information about the topics and the co-financial partner (found by the lab!); contact Directeur de thèse - philippe.molinie@centralesupelec.fr

Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online before March 13th, 2026 Midnight Paris time!