Fritz Haber Institute of the Max Planck Society, Department of Chemical Physics, Faradayweg 4-6, D-14195 Berlin, Germany.
Ultramicroscopy. 2013 Mar;126:23-32. doi: 10.1016/j.ultramic.2012.11.004. Epub 2012 Nov 23.
The positive effect of double aberration correction in x-ray induced Photoelectron Emission Microscopy (XPEEM) has been successfully demonstrated for both, the lateral resolution and the transmission, using the Au 4f XPS peak for element specific imaging at a kinetic energy of 113 eV. The lateral resolution is improved by a factor of four, compared to a non-corrected system, whereas the transmission is enhanced by a factor of 5 at a moderate resolution of 80 nm. With an optimized system setting, a lateral resolution of 18 nm could be achieved, which is up to now the best value reported for energy filtered XPEEM imaging. However, the absolute resolution does not yet reach the theoretical limit of 2 nm, which is due to space charge limitation. This occurs along the entire optical axis up to the contrast aperture. In XPEEM the pulsed time structure of the exciting soft x-ray light source causes a short and highly intense electron pulse, which results in an image blurring. In contrast, the imaging with elastically reflected electrons in the low energy electron microscopy (LEEM) mode yields a resolution clearly below 5 nm. Technical solutions to reduce the space charge effect in an aberration-corrected spectro-microscope are discussed.
在 X 射线诱导光电子发射显微镜（XPEEM）中，双像差校正的积极影响已成功地通过 Au 4f XPS 峰在 113 eV 的动能下用于元素特异性成像得到证明。与非校正系统相比，横向分辨率提高了四倍，而在中等分辨率为 80nm 时，透过率提高了五倍。通过优化系统设置，可以实现 18nm 的横向分辨率，这是迄今为止报道的能量过滤 XPEEM 成像的最佳值。然而，绝对分辨率尚未达到 2nm 的理论极限，这是由于空间电荷限制。这种限制发生在整个光轴上，直到对比度孔径。在 XPEEM 中，激发软 X 射线光源的脉冲时间结构会导致短暂而强烈的电子脉冲，从而导致图像模糊。相比之下，在低能电子显微镜（LEEM）模式下用弹性反射电子进行成像的分辨率明显低于 5nm。讨论了减少校正光谱显微镜中空间电荷效应的技术解决方案。
