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Chromium-scandium multilayer mirrors for the nitrogen K(alpha) line in the water window region

: Kuhlmann, T.; Yulin, S.; Feigl, T.; Kaiser, N.; Gorelik, T.; Kaiser, U.; Richter, W.


Applied optics 41 (2002), Nr.10, S.2048-2052
ISSN: 0003-6935
ISSN: 1539-4522
ISSN: 1559-128X
Fraunhofer IOF ()
Cr-Sc multilayer mirror; water window region; x-ray source; x-ray reflectivity; growth parameter; magnetron sputtering process; bias voltage; film growth; multilayer film quality; transmission electron microscopy; synchrotron radiation; near-normal incidence

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 K/sub alpha / 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 K/sub alpha / x-ray reflection and transmission electron microscopy. The reflective properties of the multilayers close to the nitrogen K/sub alpha / line were measured with synchrotron radiation for different angles of incidence. Reflectivities between R = 5.9% for near-normal incidence ( theta = 1.5 degrees ) and R = 29.6% for theta = 59.9 degrees were measured.