摘要
We apply charged-particle simulation to determine the constraints imposed additionally on the photoemission electron microscope (PEEM) when x rays are applied to image buried objects. PEEM initiates its image acquisition by reading the electron-emission profile on the specimen surface, but the profile is not invariant if the electrons originate from a buried object. In this work, we show that, other than the anticipated intensity reduction, the electron-emission profile projected from a buried object displays a blurrier edge for a deeper burial, whereas the distribution of an emission angle becomes narrower for electrons carrying greater kinetic energy. The burial not only redefines the objects seen by PEEM but also introduces additional depth and energy dependence to the resulted images. We demonstrate that inserting a contrast aperture in the PEEM lens can improve the image quality and ease the burial dependence.