A linear zone plate named multilayer laue lens （MLL） is fabricated using a depth-graded multilayer structure. The lens shows considerable potential in focusing an X-ray beam into a nanometer scale with high efficiency. In this letter, a depth-graded multilayer consisting of 324 alternating WSi2 and Si layers with a total thickness of 7.9μm is deposited based on the thickness sequence according to the demands of the zone plate law. Subsequently, the multilayer sample is sliced and thinned to an ideal depth along the cross-section direction using raw abrasives and diamond lapping. Finally, the cross-section is polished by a chemical mechanical polishing （CMP） technique to remove the damages and improve the surface smoothness. The final depth of the MLL is approximately 7 μm with an achieved aspect ratio greater than 400. Results of scanning electron microscopy （SEM） and atomic force microscopy （AFM） indicate that interfaces are sharp, and the multilayer structure remains undamaged after the thinning and polishing processes. The surface roughness achieved is 0.33 nm.
To develop high quality dispersion optics in the X-ray region, the sliced multilayer transmission grating is examined. Dynamical diffraction theory is used to calculate the diffraction property of this volume grating. A WSi2/Si multilayer with a d-spacing of 14.3 nm and bi-layer number of 300 is deposited on a super- polished silicon substrate by direct current magnetron sputtering technology. To make the transmission grating, the multilayer is sliced and thinned in the cross-section direction to a depth of 23-25 ttm. The diffraction efficiency of the grating is measured at E = 8.05 keV, and the lst-order efficiency is 19%. The sliced multilayer grating with large aspect ratio and nanometer period can be used for high efficiency and high dispersion optics in the X-ray region.
The multilayer Laue lens （MLL） is a novel diffraction optics which can realize nanometer focusing of hard X-rays with high efficiency. In this paper, a 7.9 μm-thick MLL with the outmost layer thickness of 15 nm is designed based on dynamical diffraction theory. The MLL is fabricated by first depositing the depth-graded multilayer using direct current （DC） magnetron sputtering technology. Then, the multilayer sample is sliced, and both cross-sections are thinned and polished to a depth of 35–41 μm. The focusing property of the MLL is measured at the Shanghai Synchrotron Facility （SSRF）. One-dimensional （1D） focusing resolutions of 205 nm and 221 nm are obtained at E=14 keV and 18 keV, respectively. It demonstrates that the fabricated MLL can focus hard X-rays into nanometer scale.
