Abstract

The DC magnetron sputter grown Co/Ti multilayers, with ultra-low bi-layer thicknesses and with Co layers deposited under mixed ambience of argon and dry air, have been investigated for use in the water window soft x-ray regime of 23–44 Å. Initially, deposition parameters have been optimized for obtaining smooth and continuous low thickness Co and Ti single-layer films, and, then, multilayers with five bi-layers of various bi-layer thicknesses were deposited. The samples have been primarily characterized by the grazing incidence x-ray reflectivity (GIXR) measurements with a hard x-ray laboratory source. Subsequently, a set of multilayers with an increasing number of bi-layers has been deposited with a constant bi-layer thickness of 42 Å. GIXR results show that hard x-ray reflectivity at the first Bragg peak is maximum for the 20 bi-layer sample, beyond which the reflectivity decreases. Finally, the samples with the most promising hard x-ray GIXR have been used for soft x-ray reflectivity measurement with synchrotron radiation, and $\sim 2.5\%$ peak reflectivity has been obtained in the multilayer sample at a 30.7 Å wavelength for a 21.5° grazing angle of incidence. The fitting results for both hard and soft x-ray reflectivities have been thoroughly investigated to find out the cause of the saturation of reflectivity with the increase in the number of bi-layers.

© 2017 Optical Society of America

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