Chromium–scandium (Cr–Sc) is a promising material combination for multilayer mirrors in the water window region. A possible x-ray source for laboratory use in this wavelength range is the nitrogen Kα line at 3.16 nm. High reflectivities at this wavelength can be achieved with Cr–Sc multilayer mirrors if the interfaces between adjacent layers are smooth. The growth parameters of the magnetron sputtering process for these materials have been optimized. It is shown that the reflectivity of such mirrors can be considerably improved by the application of a proper bias voltage during film growth. The high quality of the multilayer films is demonstrated with copper Kα x-ray reflection and transmission electron microscopy. The reflective properties of the multilayers close to the nitrogen Kα line were measured with synchrotron radiation for different angles of incidence. Reflectivities between R = 5.9% for near-normal incidence (θ = 1.5°) and R = 29.6% for θ = 59.9° were measured.
© 2002 Optical Society of America
Original Manuscript: May 29, 2001
Revised Manuscript: September 24, 2001
Published: April 1, 2002
Thomas Kuhlmann, Sergey Yulin, Torsten Feigl, Norbert Kaiser, Tatiana Gorelik, Ute Kaiser, and Wolfgang Richter, "Chromium–scandium multilayer mirrors for the nitrogen K α line in the water window region," Appl. Opt. 41, 2048-2052 (2002)