RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan.
Quantum-Phase Electronics Center and Department of Applied Physics, The University of Tokyo, Hongo, Tokyo 113-8656, Japan.
Nano Lett. 2023 Apr 12;23(7):2490-2495. doi: 10.1021/acs.nanolett.2c03938. Epub 2023 Mar 21.
Optically induced GHz-THz guided acoustic waves have been intensively studied because of the potential to realize noninvasive and noncontact material inspection. Although the generation of photoinduced guided acoustic waves utilizing nanostructures, such as ultrathin plates, nanowires, and materials interfaces, is being established, experimental characterization of these acoustic waves in consideration of the finite size effect has been difficult due to the lack of experimental methods with nm × ps resolution. Here we experimentally observe the sub-micrometer guided acoustic waves in a nanofabricated ultrathin silicon plate by ultrafast transmission electron microscopy with nm × ps precision. We successfully characterize the excited guided acoustic wave in frequency-wavenumber space by applying Fourier-transformation analysis on the bright-field movie. These results suggest the great potential of ultrafast transmission electron microscopy to characterize the acoustic modes realized in various nanostructures.
由于有望实现非侵入式和非接触式材料检测，光诱导的太赫兹导声波得到了广泛研究。尽管利用纳米结构（如超薄板、纳米线和材料界面）产生光致导声波的技术已经确立，但由于缺乏具有纳米×皮秒分辨率的实验方法，考虑到有限尺寸效应，对这些声波进行实验表征一直具有挑战性。在这里，我们通过具有纳米×皮秒精度的超快透射电子显微镜实验观察到了纳米制造的超薄硅片中的亚微米导声波。我们通过对明场电影进行傅里叶变换分析，成功地在频波数空间中对激发的导声波进行了特征描述。这些结果表明，超快透射电子显微镜在表征各种纳米结构中实现的声波模式方面具有巨大的潜力。
