Hard x-ray photoemission using standing-wave excitation applied to the MgO/Fe interface

Abstract

Many applications in electronics and spintronics rely on interfaces, which are buried a few nanometers deep and thus are hardly accessible in real devices except for invasive techniques. Here, we report on hard x-ray photoemission spectroscopy combined with the x-ray standing-wave technique as a noninvasive method to access buried interfaces with a depth resolution of a few \AA{} and enhanced interface sensitivity. Within these experiments, the film thicknesses and also the thicknesses of the intermixing layers are determined. We extend the data analysis scheme previously developed for soft x-rays to the hard x-ray regime and apply the method to buried epitaxial Fe/MgO interfaces, which play a crucial role in magnetic tunnel junctions and their applications. It was found that there was no detectable intermixing or reaction of the Fe and MgO layers at the interface.