Probing gigahertz coherent acoustic phonons in TiO2 mesoporous thin films

• Published in: Photoacoustics (Munich) Vol. 30; p. 100472
• Main Authors: Cardozo de Oliveira, E.R., Xiang, C., Esmann, M., Lopez Abdala, N., Fuertes, M.C., Bruchhausen, A., Pastoriza, H., Perrin, B., Soler-Illia, G.J.A.A., Lanzillotti-Kimura, N.D.
• Format: Journal Article
• Language: English
• Published: Elsevier GmbH 01-04-2023; Elsevier
• Subjects: Acoustic phonons; Acoustic resonators; Acoustics multilayers; Coherent phonons; Condensed Matter; Mesoporous thin films; Physics; Picosecond ultrasonics; Pump-probe; Picosecond ultrasonics; Coherent phonons; Pump-probe; Mesoporous thin films; Acoustic phonons; Acoustic resonators; Acoustics multilayers
• ISSN: 2213-5979; 2213-5979
• DOI: 10.1016/j.pacs.2023.100472

Ultrahigh-frequency acoustic-phonon resonators usually require atomically flat interfaces to avoid phonon scattering and dephasing, leading to expensive fabrication processes, such as molecular beam epitaxy. Mesoporous thin films are based on inexpensive wet chemical fabrication techniques that lead to relatively flat interfaces regardless the presence of nanopores. Here, we report mesoporous titanium dioxide-based acoustic resonators with resonances up to 90 GHz, and quality factors from 3 to 7. Numerical simulations show a good agreement with the picosecond ultrasonics experiments. We also numerically study the effect of changes in the speed of sound on the performance of the resonator. This change could be induced by liquid infiltration into the mesopores. Our findings constitute the first step towards the engineering of building blocks based on mesoporous thin films for reconfigurable optoacoustic sensors.