School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Ultramicroscopy. 2012 Mar;114:31-7. doi: 10.1016/j.ultramic.2011.12.001. Epub 2011 Dec 29.
Here we present the first atomic resolution TEM imaging at 40 keV using an aberration-corrected, monochromated source TEM. Low-voltage High-Resolution Electron Microscopy (LVHREM) has several advantages, including increased cross-sections for inelastic and elastic scattering, increased contrast per electron and improved spectroscopy efficiency, decreased delocalization effects and reduced knock-on damage. Together, these often improve the contrast to damage ratio obtained on a large class of samples. Third-order aberration correction now allows us to operate the TEM at low energies while retaining atomic resolution, which was previously impossible. At low voltage the major limitation to resolution becomes the chromatic aberration limit. We show that using a source monochromator we are able to reduce the effect of chromatic aberration and achieve a usable high-resolution limit at 40 keV to less than 1Å. We show various materials' examples of the application of the technique to image graphene and silicon, and compare atomic resolution images with electron multislice simulations.
在这里，我们展示了使用经过像差校正的单色源透射电子显微镜在 40keV 下进行的首次原子分辨率 TEM 成像。低压高分辨率电子显微镜 (LVHREM) 具有多个优点，包括增加了非弹性和弹性散射的横截面、每电子增加的对比度和改进的光谱效率、减少了离域效应和减少了碰撞损伤。这些通常共同提高了在一大类样品上获得的对比损伤比。三阶像差校正现在允许我们在保持原子分辨率的同时在低能量下操作 TEM，这在以前是不可能的。在低电压下，分辨率的主要限制因素成为色差限制。我们表明，使用源单色仪，我们能够减小色差的影响，并在 40keV 时达到小于 1Å 的可用高分辨率限制。我们展示了该技术在成像石墨烯和硅方面的各种材料的应用示例，并将原子分辨率图像与电子多晶模拟进行了比较。
