X-ray optical properties of molybdenum-carbon, molybdenum-silicon, and nickel-carbon multilayers

We have fabricated multilayer reflectors of molybdenum-carbon, molybdenum-silicon, and nickel-carbon for x rays of 1–200 Å with an electron beam evaporation method in ultrahigh vacuum. The multilayers were deposited on flat and figured substrates of float glass and superpolished glass with a surface roughness of 2–3 Å (rms). The thickness of a layer pair and the number of layer pairs were 30–100 Å and 10–20, respectively. The x-ray characteristics of these multilayer reflectors were evaluated in the 1.5–200 Å region with characteristic x rays (Cu-Kα, Si-Kα, Al-Kα, and C-Kα) and monochromatized synchrotron radiation. Peak reflectivities of molybdenum-carbon were found to be 70% at Cu-Kα and 40% at Al-Kα in grazing incidence and those of molybdenum-silicon to be more than 30% in the 150–170 Å band in near-normal incidence. On the basis of these experimental results, the x-ray optical properties of multilayers are discussed.