Thermal stability studies of short period Sc/Cr and Sc/B₄C/Cr multilayers

Abstract

The stability of short period Sc/Cr and Sc/B₄C/Cr multilayers was investigated over a large temperature range. The aim was to find a stable reflective coating for an off-axis parabola for focusing x rays from a soft x-ray free-electron laser. Normal incidence reflectivity, surface roughness, and intrinsic stress were investigated as a function of annealing temperature and two samples were also studied with a high-resolution transmission electron microscope (TEM), a scanning TEM, and through electron energy loss spectroscopy (EELS). Interface-engineered Sc/B₄C/Cr multilayers showed increased thermal stability and higher reflectivity as compared to pure Sc/Cr multilayers.

Cr/B4C multilayer mirrors: Study of interfaces and X-ray reflectance

“…6 B 4 C thin layers have also been introduced as barrier layers in Cr-based multilayers, such as Cr/Sc or Cr/V. [20][21][22] Moreover, promising designs have been reported using Cr/B 4 C multilayers, for instance, narrowband mirrors near the Cr K-edge 23 and broadband mirrors with aperiodic multilayers. 24 Cr/B 4 C is also an attractive candidate material pair for mirrors operating at photon energies just below the Cr L 2,3 -edge, due to the reduced Cr absorption which leads to enhanced reflectance.…”

Attosecond Pulse Shaping by Multilayer Mirrors

“…Ultrashort soft X-ray radiation bursts with a few femtoseconds (10 −15 s) to attosecond (10 −18 s) pulse durations have become accessible over the past few years. This was possible due to advanced laser technology in high harmonic generation (HHG) [23] or advanced electron accelerator technology in free electron lasers (FEL) [24]. The application of multilayer optics to the formation and handling of these pulses has only recently been discussed in the literature; however, it is gaining increasing attention from the scientific community.…”

Enhancement of soft X-ray reflectivity and interface stability in nitridated Pd/Y multilayer mirrors

“…In spite of impressive progress in the fabrication technology of multilayer mirrors for soft Xray (SXR) and extreme ultraviolet (EUV) radiation, these high-quality mirrors were developed for several spectral regions only. Among them are the Mo/Si multilayers for EUV lithography (λ = 13.5 nm; experimentally achieved reflectivity at normal incidence R = 70.3%) [1], La-containing multilayers for "beyond EUV" lithography (λ ~6.7 nm, R = 64%) [2,3], Al-containing multilayers for solar astronomy (λ ~17-30 nm, R = 53%) [4][5][6] and multilayers for SXR microscopy in the "water window" region (λ ~2.3-4.4 nm, R max = 32%) [7][8][9]. At the same time, all of these multilayers are poorly suited for the 8-12 nm spectral region, which is of particular interest for solar astronomy [4] and a free-electron laser beamline [10].…”