Characterization of Pd/Y multilayers with B4C barrier layers using GIXR and x-ray standing wave enhanced HAXPES

TL;DR

This study characterizes Pd/Y multilayers with B4C barrier layers using GIXR and x-ray standing wave enhanced HAXPES, revealing how B4C reduces interdiffusion and detailing interface chemistry and composition.

Contribution

It introduces a combined use of GIXR and x-ray standing wave HAXPES to analyze multilayer interfaces and chemical stability, providing new insights into interface chemistry and diffusion control.

Findings

B4C barrier layers effectively reduce Pd-Y interdiffusion.

Y forms chemical compounds with B or C at interfaces, stabilizing the multilayers.

The depth distribution of elements can be accurately interpreted from photoemission data.

Abstract

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.