Chemistry Department, Physical Chemistry with Focus on Catalysis, Technical University of Munich (TUM), Lichtenbergstr 4, Garching D-85748, Germany.
Chemistry Department, Physical Chemistry with Focus on Catalysis, Technical University of Munich (TUM), Lichtenbergstr 4, Garching D-85748, Germany.
Ultramicroscopy. 2023 Aug;250:113756. doi: 10.1016/j.ultramic.2023.113756. Epub 2023 May 9.
Non-isochromatism in X-ray PhotoEmission Electron Microscopy (XPEEM) may result in unwanted artifacts especially when working with large field of views. The lack of isochromatism of XPEEM images may result from multiple factors, for instance the energy dispersion of the X-rays on the sample or the effect of one or more dispersive elements in the electron optics of the microscope, or the combination of both. In practice, the photon energy or the electron kinetic energy may vary across the image, complicating image interpretation and analysis. The effect becomes severe when imaging at low magnification upon irradiation with high energy photons. Such imaging demands for a large X-ray illuminating spot size usually achieved by opening the exit slit of the X-ray monochromator while reducing the monochromaticity of the irradiating light. However, we show that the effect is linear and can be fully removed. A versatile correction procedure is presented which leads to true monochromatic photoelectron images at improved signal-to-noise ratio. XPEEM data recorded at the nanospectroscopy beamline of the Elettra synchrotron radiation facility illustrate the working principle of the procedure. Also, reciprocal space XPEEM data such as angle-resolved photoelectron spectroscopy (ARPES) momentum plots suffer from linear energy dispersion artifacts which can be corrected in a similar way. Representative data acquired from graphene synthesized on copper by chemical vapor deposition prove the benefits of the correction procedure.
X 射线光电子发射电子显微镜（XPEEM）中的非等色性可能会导致不需要的伪影，特别是在处理大视场时。XPEEM 图像的非等色性可能由多种因素引起，例如样品上 X 射线的能量色散或显微镜电子光学中的一个或多个色散元件的影响，或者两者的组合。在实践中，光子能量或电子动能可能会在图像中发生变化，这使得图像解释和分析变得复杂。当用高能光子以低放大倍率成像时，这种影响会变得更加严重。这种成像需要大的 X 射线照明光斑尺寸，通常通过打开 X 射线单色仪的出射狭缝来实现，同时降低辐照光的单色性。然而，我们表明这种影响是线性的，可以完全消除。提出了一种通用的校正程序，该程序可以在提高信噪比的情况下获得真正的单色光电子图像。在 Elettra 同步辐射设施的纳米光谱学光束线上记录的 XPEEM 数据说明了该程序的工作原理。此外，像角分辨光电子能谱（ARPES）动量图这样的倒空间 XPEEM 数据也会受到线性能量色散伪影的影响，可以通过类似的方式进行校正。从化学气相沉积在铜上合成的石墨烯获得的代表性数据证明了校正程序的好处。
