Depth-resolved ARPES of buried layers and interfaces via soft x-ray standing-wave excited photoemission

We introduce a new depth-selective photoemission technique, achieved by combining soft x-ray ARPES with standing-wave (SW) excited photoelectron spectroscopy, wherein the intensity profile of the exciting x-ray radiation is tailored within the sample. This effect is accomplished by setting-up an x-ray standing-wave field within the sample by growing it on a synthetic periodic multilayer mirror substrate, which in first-order Bragg reflection acts as the standing-wave generator. The antinodes of the standing wave function as epicenters for photoemission and can be moved vertically through the buried layers and interfaces by scanning the x-ray incidence angle. The new SW-ARPES technique is then applied to the investigation of the electronic properties of the buried interface within a magnetic tunnel junction La0.7Sr0.3MnO3/SrTiO3. The experimental results are compared to the state-of-art one-step photoemission theory including matrix element effects.