Veselá Petra, Hlubučková Martina, Kanclíř Vít, Václavík Jan, Žídek Karel
Institute of Plasma Physics of the Czech Academy of Sciences, U Slovanky 2525/1a, 182 00, Prague, Czech Republic.
Sci Rep. 2025 Aug 9;15(1):29145. doi: 10.1038/s41598-025-14534-7.
This work describes a previously overlooked source of measurement drift in picosecond acoustics experiments and demonstrates a solution for ensuring long-term measurement reliability. Picosecond acoustics is a well-suited non-destructive characterization technique used for determining film thickness, elastic properties, and interface quality in multilayer systems. We reveal that significant changes in measured signals develop over time in thin-film stacks studied by picosecond sonar. These temporal variations occur rapidly after sample deposition and persist for months, manifesting most prominently in the thermal exponential background, but also affecting echo shapes and Brillouin oscillation phases. Our systematic investigation demonstrates that these measurement drifts originate from aging of the titanium transducer layer when exposed to ambient atmosphere. Such aging effects can compromise data reliability when comparing measurements taken at different times or when analyzing subtle signal features. To avoid this issue, we show that the signal variation can be completely eliminated by passivating the Ti layer with a thin 10 nm Si₃N₄ coating. These results provide guidance for reliable picosecond acoustics characterization and highlight the critical importance of considering transducer stability in ultrafast acoustics.
这项工作描述了皮秒声学实验中一个先前被忽视的测量漂移源，并展示了一种确保长期测量可靠性的解决方案。皮秒声学是一种非常适合用于确定多层系统中薄膜厚度、弹性特性和界面质量的无损表征技术。我们发现，在皮秒声纳研究的薄膜堆栈中，测量信号会随着时间发生显著变化。这些时间变化在样品沉积后迅速出现，并持续数月，在热指数背景中表现最为明显，但也会影响回波形状和布里渊振荡相位。我们的系统研究表明，这些测量漂移源于钛换能器层暴露在环境大气中时的老化。当比较不同时间进行的测量或分析细微的信号特征时，这种老化效应会损害数据可靠性。为避免这个问题，我们表明通过用10纳米厚的Si₃N₄薄膜钝化钛层，可以完全消除信号变化。这些结果为可靠的皮秒声学表征提供了指导，并突出了在超快声学中考虑换能器稳定性的至关重要性。
