  Pd/Y multilayers are high reflectance mirrors designed to work in the 7.5-11
nm wavelength range. Samples, prepared by magnetron sputtering, are deposited
with or without B4C barrier layers located at the interfaces of Pd and Y layers
to reduce interdiffusion, which is expected by calculating mixing enthalpy of
Pd and Y. Grazing incident x-ray reflectometry is used to characterize these
multilayers. B4C barrier layers are found effective on reducing the Pd-Y
interdiffusion. Details of the composition of the multilayers are revealed by
hard x-ray photoemission spectroscopy under x-ray standing waves effect. It
consists in measuring the photoemission intensity from samples that perform an
angular scan in the region corresponding to the multilayer period and the
incident photon energy according to the Bragg law. The experimental result
indicates that Pd does not chemically react with B nor C at the Pd-B4C
interfaces while Y does at the Y-B4C interfaces. The formation of Y-B or Y-C
chemical compound can be the reason why the interfaces are stabilized. By
comparing the experimentally obtained angular variation of the characteristic
photoemission with the theoretical calculation, the depth distribution of each
component element can be interpreted.
