Nanometer Linear Focusing of Hard X Rays by a Multilayer Laue Lens

Abstract

We report on a type of linear zone plate for nanometer-scale focusing of hard x rays, a multilayer Laue lens (MLL), produced by sectioning a multilayer and illuminating it in Laue diffraction geometry. Because of its large optical depth, a MLL spans the diffraction regimes applicable to a thin Fresnel zone plate and a crystal. Coupled wave theory calculations indicate that focusing to 5 nm or smaller with high efficiency should be possible. Partial MLL structures with outermost zone widths as small as 10 nm have been fabricated and tested with 19.5 keV synchrotron radiation. Focal sizes as small as 30 nm with efficiencies up to 44% are measured.

Hard x-ray scanning microscopy with coherent radiation: Beyond the resolution of conventional x-ray microscopes

“…3 In conventional x-ray microscopy the spatial resolution is currently limited to a few 10 nm, 3 mainly due to aberrations and the limited numerical aperture of today's x-ray optics. [4][5][6][7] By combining scanning microscopy with coherent x-ray diffraction imaging this limit can be overcome. In recent years, scanning coherent diffraction microscopy, also known as ptychography, has been rediscovered 8 and introduced into the field of x-ray imaging.…”

“…In addition, the lateral coherence length at the instrument can be adjusted by prefocusing optics. 19 Inside the scanning microscope, the beam is usually focused by a pair of crossed nanofocusing refractive x-ray lenses made of silicon 4,20 but other optics, such as Fresnel zone plates 6 and multilayer Laue lenses 5 can be used, as well. By means of x-ray fluorescence, absorption, and (coherent) scattering, this scanning microscope can image specimens with elemental, chemical, and structural contrast, respectively.…”

3D Nanofabrication of High‐Resolution Multilayer Fresnel Zone Plates

“…It is known that FZPs with zones that are parallel to the optical axis come with extreme penalties to the focusing efficiencies at small Δ r ( Figure 5 e–h) due to wave coupling effects 59, 65. This negates one of the main advantages of fabricating FZPs via thin film deposition techniques, namely, the possibility to deposit extremely fine outermost zones for high resolution optics.…”

Takagi-Taupin description of x-ray dynamical diffraction from diffractive optics with large numerical aperture

“…Progress in the fabrication of x-ray optics has pushed the spatial resolution of hard x-ray microscopes and -microprobes to well below 100 nm using Kirk Patrick-Baez (K-B) mirrors 1,2,3,4 , refractive lenses 5 and diffractive optics 6,7 . This makes hard x-ray microscopy and spectromicroscopy powerful tools to probe the structure and properties of materials at the nanoscale, with the advantages of good penetration, which provides for the study of thick specimens and buried structures.…”

“…The fabrication approach provides high aspect ratios, and is therefore well suited for hard x-ray focusing 12 . Initial 1-D MLL structures have achieved a line focus of 30 nm in the hard x-ray range (19.5 keV) with a diffraction efficiency of more than 40% 6 .…”