<title>Hard x-ray multilayers: a study of different material systems</title>

Multilayer structures with depth-graded spacing can show a high reflectivity in a broad energy passband for hard X-rays if the interface roughness/diffuseness is controlled and minimized. We present a study of several multilayer systems deposited by DC magnetron sputtering on <111> silicon wafers and superpolished fused silica substrates. The material combinations discussed are W/Si, WSi₂/Si, W/C, Pt/C, Ni/C, Ni/B₄C, and Mo/Si. The deposition method used was DC magnetron sputtering at low argon pressures (1.5 to 5 mT). The characterization methods used were: Atomic Force Microscopy in tapping mode, stylus profilometry, Rutherford backscattering, cross sectional TEM, and specular X-ray reflectivity (XRR) scans at 8.05 keV. Different process parameters were varied in order to optimize the interface roughness/diffuseness (sigma) that was measured by XRR scans.