Depth-resolved soft x-ray photoelectron emission microscopy in nanostructures via standing-wave excited photoemission

We extend conventional laterally-resolved soft x-ray photoelectron emission microscopy to provide depth resolution along the surface normal down to a few angstroms. This is achieved by using standing-wave excitation. The sample is a Ag/Co/Au trilayer, grown on a Si/MoSi2 multilayer mirror, with the bottom Ag layer in a wedge profile. Tuning the incident x-ray to the mirror Bragg angle sets up a standing x-ray wave field in the multilayer and the trilayer wedge structure. We demonstrate the resulting depth resolution by imaging the standing-wave fields as they move through the trilayer wedge structure