title: Enhancement of soft X-ray reflectivity and interface stability in nitridated Pd/Y multilayer mirrors.
abstract: Pd/Y multilayer mirrors operating in the soft X-ray region are characterized by a high theoretical reflectance, reaching 65% at normal incidence in the 8-12 nm wavelength range. However, a severe intermixing of neighboring Pd and Y layers results in an almost total disappearance of the interfaces inside the multilayer structures fabricated by direct current magnetron sputtering and thus a dramatic reflectivity decrease. Based on grazing incidence X-ray reflectometry and X-ray photoelectron spectroscopy, we demonstrate that the stability of the interfaces in Pd/Y multilayer structures can be essentially improved by adding a small amount of nitrogen (4-8%) to the working gas (Ar). High resolution transmission electron microscopy shows that the interlayer width is only 0.9 nm and 0.6 nm for Y(N)-on-Pd(N) and Pd(N)-on-Y(N) interfaces, respectively. A well-defined crystalline texture of YN (200) is observed on the electron diffraction pattern. As a result, the measured reflectance of the Pd(N)/Y(N) multilayer achieves 30% at λ = 9.3 nm. The peak reflectivity value is limited by the remaining interlayers and the formation of the YN compound inside the yttrium layers, resulting in an increased absorption.
authors.forename: Dechao
authors.initials: D
authors.lastname: Xu
authors.forename: Qiushi
authors.initials: Q
authors.lastname: Huang
authors.forename: Yiwen
authors.initials: Y
authors.lastname: Wang
authors.forename: Pin
authors.initials: P
authors.lastname: Li
authors.forename: Mingwu
authors.initials: M
authors.lastname: Wen
authors.forename: Philippe
authors.initials: P
authors.lastname: Jonnard
authors.forename: Angelo
authors.initials: A
authors.lastname: Giglia
authors.forename: Igor V
authors.initials: IV
authors.lastname: Kozhevnikov
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Zhanshan
authors.initials: Z
authors.lastname: Wang