High-frequency guided elastic waves in thin films of lithium niobate on sapphire

This thesis is part of the ANR MAXSAW project, which aims to develop new components operating in the RF domain, adapted to the new 5G frequencies. Surface acoustic wave (SAW) filters are widely used to distinguish the different frequencies of RF signals. Unfortunately, the frequency of conventional SAW filters is limited to 3.7 GHz. Epitaxial thin films of LiNbO₃ on sapphire host guided acoustic waves that meet the demand for higher frequencies and efficiency.

We first produced LiNbO₃ thin films on sapphire substrates. Thin films of good crystalline quality were obtained. We also studied their acoustic properties using simulations, and confirmed the frequencies achievable with these structures.

Then, we simulated, designed and characterized SAW resonators based on LiNbO₃ thin films deposited on sapphire, and compared them with the state of the art. Promising acoustic devices were obtained. Finally, an application to the MAXSAW project is presented.

electrical characterisation, physical properties, piezoelectricity, acoustic waves, lithium niobate

This Thesis is embargoed until 23/09/2026.