Probing Gigahertz Coherent Acoustic Phonons in TiO$_{2}$ Mesoporous Thin Films

• Main Authors: de Oliveira, E. R. Cardozo, Xiang, C, Esmann, M, Abdala, N. Lopez, 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: 19-12-2022
• Subjects: Physics - Mesoscale and Nanoscale Physics
• DOI: 10.48550/arxiv.2212.09684

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. In contrast, mesoporous
thin films are based on inexpensive wet chemical fabrication techniques. 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.