Sébastien AUBERT : ""Investigation of a surface acoustic wave phononic resonator for applications to temperature and strain sensing"

PhD Thesis Works of Sébastien Aubert :""Investigation of a surface acoustic wave phononic resonator for applications to temperature and strain sensing""

Abstract :

Surface acoustic wave resonators can be used as sensors for temperature and strain monitoring. The idea is to take advantage of the variation in frequency of the resonators that depends on the measured quantity. Currently, the technology used, based on Bragg mirrors, shows its limits in terms of performance at high frequencies (above 1 GHz). The aim of this PhD thesis work was to study the potential and performance of a new technology based on the use of phononic crystals. This technology refers to periodically arranged materials, acting on acoustic waves’ propagation. Phononic crystals represent an alternative to classical Bragg mirror technology, allowing an omnidirectional spatial confinement and an additional degree of freedom for optimization. A square lattice pillar based phononic crystal was theoretically and experimentally investigated. Based on the combination of Bragg scattering and local resonances, we were able to create acoustic band gaps that could be exploited. The operating frequency considered was about 450 MHz, using nickel electroplating to fabricate pillars. In this frequency range, we demonstrated the presence of acoustic band gaps using wide band electrical characterization. A phononic resonator was designed, fabricated and characterized by electrical and optical methods. A quality factor of about 950 was obtained, with total reflection of acoustic wave reached within less than ten periods. Comparison of measurements and simulations allowed us to explain the acoustic phenomena involved.

The jury will consist of: :

Emmanuel Le Clésio, Reporting jury, Professor at university of Montpellier

Abdelkrim Talbi, Reporting jury, Associate professor at école Centrale de Lille

Sarah Benchabane, Examiner, CNRS researcher at Femto-st institute

Omar Elmazria, Examiner, Professor at university of Lorraine

Abdelkrim Khelif, Thesis Director, CNRS research director at Femto-st institute

Luc Chommeloux, Industrial supervisor, Product development director at SENSeOR SAS

Localization : Aiditorium JJ Gagnepain - TEMIS Site, ground floor - 15B, Avenue des Montboucons - Besançon