探测TiO $_{2}$介孔薄膜中的吉赫相干声学声子
Probing Gigahertz Coherent Acoustic Phonons in TiO$_{2}$ Mesoporous Thin Films
摘要：
超高频声-声子谐振器通常需要原子级平坦的界面以避免声子散射和失相，从而导致昂贵的制造工艺，例如分子束外延。相比之下，中孔薄膜是基于廉价的湿化学制造技术。在这里，我们报告的介孔二氧化钛基声谐振器的谐振频率高达90 GHz，和品质因数从3至7。数值模拟结果与皮秒超声实验结果吻合较好。我们还数值研究了声速的变化对谐振器性能的影响。这种变化可能是由液体渗入介孔引起的。我们的研究结果构成了第一步的工程积木的基础上，介孔薄膜的可重构光声传感器。
英文摘要：
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.
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