Application Of A Post Column Energy Filter

在装有柱后能量滤光片的透射电子显微镜上实现了光谱成像，目的是从纳米尺度的生物样品中获得定量的元素分布和能量损失谱。一系列多达100个1024×1024像素的能量选择图像已经用冷却的CCD相机记录下来，该相机与位于能量滤光器像面上的单晶YAG闪烁体相耦合。首先对每个序列中的单个图像进行互相关，以校正样本漂移。然后在每个像素上提取光谱，并通过外推背景并在指定的能量范围内积分信号来获得净核心边缘强度。光谱成像相对于传统的两窗或三窗EELS映射技术的优点是在估计背景强度方面提高了精度。此外，能量过滤透射式电子显微镜(EFTEM)中的光谱成像可用于从比扫描透射式电子显微镜(STEM)更大的样品区域中获得元素图谱，尽管扫描透射式电子显微镜(STEM)中的最低检测浓度较低。我们将光谱成像技术应用于电子傅立叶变换电子显微镜，绘制了富硫蛋白在分泌细胞中的分布。

Spectroscopic imaging has been implemented in a transmission electron microscope equipped with a post-column energy filter with the aim of obtaining quantitative elemental distributions and energy-loss spectra from biological specimens on a nanometer scale. Series of up to one hundred 1024x1024 pixel energy-selected images have been recorded with a cooled CCD camera coupled to a single crystal YAG scintillator situated at the image plane of the energy-filter. Individual images in each series are first cross-correlated to correct for specimen drift. Spectra are then extracted at each pixel and the net core-edge intensity is obtained by extrapolating the background and integrating the signal within a specified energy range. The advantage of spectrum-imaging over the conventional two-window or three-window EELS mapping techniques is the increased accuracy in estimating the background intensity. Furthermore, spectrum-imaging in the energy-filtering transmission electron microscope (EFTEM) can be used to acquire elemental maps from larger sample areas than is achievable in the scanning transmission electron microscope (STEM), although the minimum detectable concentrations are lower in the STEM. We have applied the spectrum-imaging technique in the EFTEM to map the distributions of sulfur-rich proteins in secretory cells.