title: Nitridated Pd/B4C multilayer mirrors for soft X-ray region: internal structure and aging effects.
abstract: Reactive sputtering with a mixture of argon and nitrogen (N2partial pressure of 4%, 8%, and 15%) as the working gas is used to develop the high reflectance Pd/B4C multilayers for soft X-ray region application. Compared to the pure Ar fabricated sample, the interface roughness of the nitridated multilayer is slightly increased while the compressive stress is essentially relaxed from -623 MPa (pure Ar) to -85 MPa (15% N2). A maximum reflectance of 32% is measured at the wavelength of 9.5 nm for the multilayer fabricated with 15% N2. After storing the multilayers in an air environment for 6-17 months, a distinct aging effect is observed on the nitridated samples. The transmission electron microscopy results indicate that a large part of the top layers of the nitridated samples is deteriorated with severe interdiffusion, essential decrease in d-spacing, and compacted multilayer structure. The deterioration is less pronounced for the multilayers fabricated with a higher ratio of N2. Energy dispersive X-ray spectroscopy reveals that the concentration of nitrogen and boron in the degraded area is much reduced compared to the intact layers. A primitive model of upward diffusion of nitrogen and boron is proposed to explain the aging effects of the nitridated structure.
authors.forename: Yiwen
authors.initials: Y
authors.lastname: Wang
authors.forename: Qiushi
authors.initials: Q
authors.lastname: Huang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Yi
authors.forename: Igor V
authors.initials: IV
authors.lastname: Kozhevnikov
authors.forename: Runze
authors.initials: R
authors.lastname: Qi
authors.forename: Mingwu
authors.initials: M
authors.lastname: Wen
authors.forename: Philippe
authors.initials: P
authors.lastname: Jonnard
authors.forename: Jinshuai
authors.initials: J
authors.lastname: Zhang
authors.forename: Angelo
authors.initials: A
authors.lastname: Giglia
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Zhanshan
authors.initials: Z
authors.lastname: Wang