Laterally graded multilayers and their applications

Laterally graded multilayers consisting of uniform W layers and wedge-shaped C layers have been made at the Advanced Photon Source deposition lab for tunable x-ray double-monochromator applications. The double monochromator has two identical graded multilayers in series, as in the conventional double-crystal monochromator arrangement. By letting the x-ray beam hit slightly different (bilayer) d spacing on each multilayer, one can adjust the bandpass and peak energy of the transmitted beam. Also, since the Bragg angles of the two multilayers are not constrained to be the same, the angle of the transmitted beam can be varied in the vertical plane. This option may be an attractive alternative to the conventional way of studying liquid surfaces in reflectivity and grazing-incidence diffraction measurements. The graded multilayer comprised 60 bilayers of W and C on 100x25x3 mm float glass with a d spacing varying from 35 to 60 Aa and an average gradient of 0.27 Aa/mm in the long direction. The films were made by dc magnetron sputtering with the sputtered atoms passing a contoured mask while the substrate was moving. Two different masks were designed to produce either a uniform (for W) or graded (for C) thickness profile. The multilayer and graded multilayers have many other novel applications. Potential applications in x-ray fluorescence detection and x-ray standing wave experiments will be discussed