title: 14.5% near-normal incidence reflectance of Cr/Sc x-ray multilayer mirrors for the water window.
abstract: Cr/Sc multilayer mirrors, synthesized by ion-assisted magnetron sputter deposition, are proved to have a high near-normal reflectivity of R = 14.5% at a grazing angle of 87.5 degrees measured at the wavelength lambda = 3.11 nm, which is an improvement of more than 31% compared with previously published results. Elastic recoil detection analyses show that the mirrors contained as much as 15 at. % of N and traces of C and O. Soft x-ray reflectivity simulations reveal interface widths of sigma = 0.34 nm and an exceptionally small layer thickness drift of approximately 1.6 x 10(-5) nm/multilayer period throughout the stack. Simulations show that a reflectivity of R = 25.6% is attainable if impurities and layer thickness drift can be eliminated. The abrupt interfaces are achieved with ion assistance with a low ion energy of 24 eV and high ion-to-metal flux ratios of 7.1 and 23.1 during Cr and Sc sputter deposition, respectively. In addition, a near-normal incidence reflectivity of 5.5% for the C VI emission line (lambda = 3.374 nm) from a laser plasma source was verified.
authors.affiliation: Thin Film Physics Division, Department of Physics, Linköping University, 58183 Linköping, Sweden. freer@ifm.liu.se
authors.forename: Fredrik
authors.initials: F
authors.lastname: Eriksson
authors.forename: Göran A
authors.initials: GA
authors.lastname: Johansson
authors.forename: Hans M
authors.initials: HM
authors.lastname: Hertz
authors.forename: Eric M
authors.initials: EM
authors.lastname: Gullikson
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kreissig
authors.forename: Jens
authors.initials: J
authors.lastname: Birch