title: Terbium-based extreme ultraviolet multilayers.
abstract: We have fabricated periodic multilayers that comprise either Si/Tb or SiC/Tb bilayers, designed to operate as narrowband reflective coatings near 60 nm wavelength in the extreme ultraviolet (EUV). We find peak reflectance values in excess of 20% near normal incidence. The spectral bandpass of the best Si/Tb multilayer was measured to be 6.5 nm full width at half-maximum (FWHM), while SiC/Tb multilayers have a more broad response, of order 9.4 nm FWHM. Transmission electron microscopy analysis of Si/Tb multilayers reveals polycrystalline Tb layers, amorphous Si layers, and relatively large asymmetric amorphous interlayers. Thermal annealing experiments indicate excellent stability to 100 degrees C (1 h) for Si/Tb. These new multilayer coatings have the potential for use in normal incidence instrumentation in a region of the EUV where efficient narrowband multilayers have not been available until now. In particular, reflective Si/Tb multilayers can be used for solar physics applications where the coatings can be tuned to important emission lines such as O V near 63.0 nm and Mg X near 61.0 nm.
authors.affiliation: Columbia Astrophysics Laboratory, New York, New York 10027, USA. windt@astro.columbia.edu
authors.forename: David L
authors.initials: DL
authors.lastname: Windt
authors.forename: John F
authors.initials: JF
authors.lastname: Seely
authors.forename: Benjawan
authors.initials: B
authors.lastname: Kjornrattanawanich
authors.forename: Yu A
authors.initials: YA
authors.lastname: Uspenskii