论文标题
通过直接电子检测启用的低温温度下的原子分辨率元素映射
Atomic-resolution elemental mapping at cryogenic temperatures enabled by direct electron detection
论文作者
论文摘要
通过扫描透射电子显微镜与电子能量损耗光谱（Stem-Eels）结合的光谱映射是确定各种材料和接口的结构和化学的强大技术。该技术向低温温度的扩展为许多领域的新实验打开了大门，包括材料物理学，能源储能和转换以及生物学。但是，这种实验通常由于样本敏感性或在不稳定的低温条件下需要快速数据采集而面临信号限制。与传统的间接检测系统（例如电荷耦合设备（CCD））相比，直接电子检测器（DEDS）提供了提高的侦探量子效率，较窄的点扩散功能以及较高的信号对噪声比率。在这里，我们将Gatan K2 Summit的性能与ultrascan 1000 ccd进行比较，以用于信号限制的原子分辨率茎 - 蜂物实验。由于其提高点的扩散函数，DED的能量分辨率在降低5倍的情况下仍可与CCD的能量分辨率相当，从而在不牺牲光谱分辨率的情况下同时访问了更广泛的总能量范围。更重要的是，直接检测的好处可实现各种低信号实验，包括在1123 eV和2580 ev时的1123 eV和1123 eV的原子分辨率映射，例如LA-M $ _ {2,3} $ EDGE，以及BI-M $ _ {4,5} $ EDGE。对于以每秒400个光谱的快速获取，与CCD相比，DED记录的元素图显示，原子晶格条纹对比度高达40％。利用这些性能的改进和K2 DED的快速读数，我们使用直接检测干eels在低温温度下展示原子分辨率元素映射。
Spectroscopic mapping by scanning transmission electron microscopy coupled with electron energy loss spectroscopy (STEM-EELS) is a powerful technique for determining the structure and chemistry of a wide range of materials and interfaces. The extension of this technique to cryogenic temperatures opens the door to new experiments across many fields including materials physics, energy storage and conversion, and biology. Such experiments, however, often face signal limitations due to sample sensitivity or the need for rapid data acquisition under less stable cryogenic conditions. Compared to traditional indirect detection systems such as charge coupled devices (CCDs), direct electron detectors (DEDs) offer improved detective quantum efficiencies, narrower point spread functions, and superior signal-to-noise ratios. Here, we compare the performance of a Gatan K2 Summit DED to an UltraScan 1000 CCD for use in signal-limited atomic-resolution STEM-EELS experiments. Due to its improved point spread function, the DED's energy resolution remains comparable to that of the CCD at a 5 times lower dispersion, providing simultaneous access to a much broader total energy range without sacrificing spectral resolution. More importantly, the benefits of direct detection enable a variety of low-signal experiments, including atomic-resolution mapping of minor and high energy edges such as the La-M$_{2,3}$ edge at 1123 eV and the Bi-M$_{4,5}$ edge at 2580 eV. For rapid acquisitions at 400 spectra per second, elemental maps recorded with the DED show an up to 40 percent increase in atomic lattice fringe contrast compared to those acquired with the CCD. Taking advantage of these performance improvements and the fast readout of the K2 DED, we use direct detection STEM-EELS to demonstrate atomic-resolution elemental mapping at cryogenic temperatures.
