Pang A B, Müller Th, Altman M S, Bauer Ernst
Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
J Phys Condens Matter. 2009 Aug 5;21(31):314006. doi: 10.1088/0953-8984/21/31/314006. Epub 2009 Jul 7.
A Fourier optics calculation of image formation in low energy electron microscopy (LEEM) is presented. The adaptation of the existing theory for transmission electron microscopy to the treatment of LEEM and other forms of cathode lens electron microscopy is explained. The calculation incorporates imaging errors that are caused by the objective lens (aberrations), contrast aperture (diffraction), imperfect source characteristics, and voltage and current instabilities. It is used to evaluate the appearance of image features that arise from phase objects such as surface steps and amplitude objects that produce what is alternatively called amplitude, reflectivity or diffraction contrast in LEEM. This formalism can be used after appropriate modification to treat image formation in other emission microscopies. Implications for image formation in the latest aberration-corrected instruments are also discussed.
本文介绍了低能电子显微镜（LEEM）中图像形成的傅里叶光学计算。解释了如何将现有的透射电子显微镜理论应用于LEEM和其他形式的阴极透镜电子显微镜的处理。该计算考虑了由物镜（像差）、对比度光阑（衍射）、不完美的源特性以及电压和电流不稳定性引起的成像误差。它用于评估由相位物体（如表面台阶）和振幅物体产生的图像特征的外观，这些物体在LEEM中产生所谓的振幅、反射率或衍射对比度。经过适当修改后，这种形式主义可用于处理其他发射显微镜中的图像形成。还讨论了最新的像差校正仪器中图像形成的影响。
