X-ray focusing with efficient high-NA multilayer Laue lenses

Saša Bajt,Manuela Kuhn,Oleksandr Yefanov,H Fleckenstein ,Kanupriya Pande,Anja Burkhardt,Karolina Stachnik,Kevin T Murray ,Joe Chen ,Valerio Mariani,David Pennicard,M Domaracký ,Yang Du,Steven Aplin,A Andrejczuk ,Henry N Chapman ,Marc Messerschmidt,A Meents ,Xiaojing Huang,Andrew J Morgan ,Yong S Chu ,P Villanueva-Pérez ,Hanfei Yan,Evgeny Nazaretski,Mauro Prasciolu,Christian Hamm

doi:10.1038/lsa.2017.162

Abstract

Multilayer Laue lenses are volume diffraction elements for the efficient focusing of X-rays. With a new manufacturing technique that we introduced, it is possible to fabricate lenses of sufficiently high numerical aperture (NA) to achieve focal spot sizes below 10 nm. The alternating layers of the materials that form the lens must span a broad range of thicknesses on the nanometer scale to achieve the necessary range of X-ray deflection angles required to achieve a high NA. This poses a challenge to both the accuracy of the deposition process and the control of the materials properties, which often vary with layer thickness. We introduced a new pair of materials—tungsten carbide and silicon carbide—to prepare layered structures with smooth and sharp interfaces and with no material phase transitions that hampered the manufacture of previous lenses. Using a pair of multilayer Laue lenses (MLLs) fabricated from this system, we achieved a two-dimensional focus of 8.4 × 6.8 nm2 at a photon energy of 16.3 keV with high diffraction efficiency and demonstrated scanning-based imaging of samples with a resolution well below 10 nm. The high NA also allowed projection holographic imaging with strong phase contrast over a large range of magnifications. An error analysis indicates the possibility of achieving 1 nm focusing.

Highlights

X-ray-based techniques enable non-destructive measurements of natural and man-made materials and provide elemental, chemical and structural information of the internal structures of these materials
We introduced a new pair of materials—tungsten carbide and silicon carbide—to prepare layered structures with smooth and sharp interfaces and with no material phase transitions that hampered the manufacture of previous lenses
high-resolution TEM (HRTEM) images of these two depth-graded multilayers are presented in Figure 2b (W/silicon carbide (SiC)) and Figure 2c (WC/SiC)

Summary

Introduction

X-ray-based techniques enable non-destructive measurements of natural and man-made materials and provide elemental, chemical and structural information of the internal structures of these materials These techniques range from diffraction of crystalline materials at the atomic scale to tomographic imaging of large organisms such as humans. There are different ways to focus X-rays[1], the most promising way to achieve a nanometer-resolution X-ray microscope is with a volume zone plate[2,3] This diffractive optical element consists of alternating layers of two materials of differing densities, with layer periods that decrease as the number of bi-layers n increases from the optic axis followpingffiffiffiffiffitffihffiffiffie Fresnel zone-plate formula given approximately by dn 1⁄4 f l=n for a focal length f and wavelength λ (see Figure 1). To achieve a lens with a high efficiency, the lens structure must be as thick as the extinction depth for diffraction, which is several micrometers for such

Methods

Results

Conclusion