Liu Chang, Ma Chaojie, Xu Jinjing, Qiao Ruixi, Sun Huacong, Li Xiaomin, Xu Zhi, Gao Peng, Wang Enge, Liu Kaihui, Bai Xuedong
School of Physics, Peking University, Beijing 100871, China.
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Rev Sci Instrum. 2021 Jan 1;92(1):013704. doi: 10.1063/5.0031115.
Exploring the corresponding relation between structural and physical properties of materials at the atomic scale remains the fundamental problem in science. With the development of the aberration-corrected transmission electron microscopy (AC-TEM) and the ultrafast optical spectroscopy technique, sub-angstrom-scale spatial resolution and femtosecond-scale temporal resolution can be achieved, respectively. However, the attempt to combine both their advantages is still a great challenge. Here, we develop in situ optical spectroscopy with high temporal resolution in AC-TEM by utilizing a self-designed and manufactured TEM specimen holder, which has the capacity of sub-angstrom-scale spatial resolution and femtosecond-scale temporal resolution. The key and unique design of our apparatus is the use of the fiber bundle, which enables the delivery of focused pulse beams into TEM and collection of optical response simultaneously. The generated focused spot has a size less than 2 µm and can be scanned in plane with an area larger than 75 × 75 µm. Most importantly, the positive group-velocity dispersion caused by glass fiber is compensated by a pair of diffraction gratings, thus resulting in the generation of pulse beams with a pulse width of about 300 fs (@ 3 mW) in TEM. The in situ experiment, observing the atomic structure of CdSe/ZnS quantum dots in AC-TEM and obtaining the photoluminescence lifetime (∼4.3 ns) in the meantime, has been realized. Further ultrafast optical spectroscopy with femtosecond-scale temporal resolution could be performed in TEM by utilizing this apparatus.
在原子尺度上探索材料结构与物理性质之间的对应关系仍然是科学中的基本问题。随着像差校正透射电子显微镜（AC-TEM）和超快光学光谱技术的发展，分别可以实现亚埃级空间分辨率和飞秒级时间分辨率。然而，将两者优势结合起来的尝试仍然是一个巨大的挑战。在此，我们通过使用自行设计和制造的TEM样品架，在AC-TEM中开发了具有高时间分辨率的原位光谱技术，该样品架具有亚埃级空间分辨率和飞秒级时间分辨率的能力。我们仪器的关键且独特的设计是使用了光纤束，它能够将聚焦脉冲光束传输到TEM中并同时收集光学响应。所产生的聚焦光斑尺寸小于2 µm，并且可以在平面内扫描大于75×75 µm的区域。最重要的是，玻璃光纤引起的正色散通过一对衍射光栅得到补偿，从而在TEM中产生脉冲宽度约为300 fs（@ 3 mW）的脉冲光束。已经实现了原位实验，即在AC-TEM中观察CdSe/ZnS量子点的原子结构并同时获得光致发光寿命（约4.3 ns）。利用该仪器可以在TEM中进一步进行具有飞秒级时间分辨率的超快光学光谱研究。
