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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 45, Iss. 1 — Jan. 1, 2006
  • pp: 137–143

Interface engineered ultrashort period Cr–Ti multilayers as high reflectance mirrors and polarizers for soft x rays of λ = 2.74 nm wavelength

Naureen Ghafoor, Per O. Å. Persson, Jens Birch, Fredrik Eriksson, and Franz Schäfers  »View Author Affiliations


Applied Optics, Vol. 45, Issue 1, pp. 137-143 (2006)
http://dx.doi.org/10.1364/AO.45.000137


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Abstract

Cr–Ti multilayers with ultrashort periods of 1.39 2.04 nm have been grown for the first time as highly reflective, soft-x-ray multilayer, near-normal incidence mirrors for transition radiation and Čherenkov radiation x-ray sources based on the Ti–2p absorption edge at E = 452 eV ( λ = 2.74 nm ) . Hard, as well as soft, x-ay reflectivity and transmission electron microscopy were used to characterize the nanostructure of the mirrors. To achieve minimal accumulated roughness, improved interface flatness, and to avoid intermixing at the interfaces, each individual layer was engineered by use of a two-stage ion assistance process during magnetron sputter deposition: The first 0.3 nm of each Ti and Cr layer was grown without ion assistance, and the remaining 0.39 0. 72 nm of the layers were grown with high ion–neutral flux ratios Φ ˙ ( Φ Ti = 3.3 , Φ Cr = 2.2 ) and a low energy E ion ( E Ti = 23.7 and E Cr = 21.2 ) , ion assistance. A maximum soft-x-ray reflectivity of R = 2.1 % at near-normal incidence ( 78.8 ° ) was achieved for a multilayer mirror containing 100 bilayers with a modulation period of 1.379 nm and a layer thickness ratio of Γ = 0.5 . For a polarizing multilayer mirror with 150 bilayers designed for operation at the Brewster angle, 45 ° , an extinction ratio, R s / R p , of 266 was achieved with an absolute reflectivity of R = 4.3 % .

© 2006 Optical Society of America

OCIS Codes
(230.4170) Optical devices : Multilayers
(310.3840) Thin films : Materials and process characterization
(340.7470) X-ray optics : X-ray mirrors

Virtual Issues
Vol. 1, Iss. 2 Virtual Journal for Biomedical Optics

Citation
Naureen Ghafoor, Per O. Å. Persson, Jens Birch, Fredrik Eriksson, and Franz Schäfers, "Interface engineered ultrashort period Cr-Ti multilayers as high reflectance mirrors and polarizers for soft x rays of lambda = 2.74 nm wavelength," Appl. Opt. 45, 137-143 (2006)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-45-1-137


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References

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