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Elsevier, Ultramicroscopy, (126), p. 23-32, 2013

DOI: 10.1016/j.ultramic.2012.11.004

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First experimental proof for aberration correction in XPEEM: Resolution, Transmission enhancement, And limitation by space charge effects

Journal article published in 2012 by Th-H. Schmidt, A. Sala ORCID, H. Marchetto, E. Umbach, H.-J. Freund
This paper is available in a repository.
This paper is available in a repository.

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Abstract

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 113eV. 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 80nm. With an optimized system setting, a lateral resolution of 18nm 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 2nm, 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 5nm. Technical solutions to reduce the space charge effect in an aberration-corrected spectro-microscope are discussed.