Achieving hard X-ray nanofocusing using a wedged multilayer Laue lens

Abstract

We report on the fabrication and the characterization of a wedged multilayer Laue lens for x-ray nanofocusing. The lens was fabricated using a sputtering deposition technique, in which a specially designed mask was employed to introduce a thickness gradient in the lateral direction of the multilayer. X-ray characterization shows an efficiency of 27% and a focus size of 26 nm at 14.6 keV, in a good agreement with theoretical calculations. These results indicate that the desired wedging is achieved in the fabricated structure. We anticipate that continuous development on wedged MLLs will advance x-ray nanofocusing optics to new frontiers and enrich capabilities and opportunities for hard X-ray microscopy.

3D Nanofabrication of High‐Resolution Multilayer Fresnel Zone Plates

“…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. Proposed solutions to this particular problem include stacking of binary FZPs to create tilted zones,18 multilayer Laue lens pairs,27, 28, 29, 30, 66 and depositing on drawn tapered fibers 67, 68. Stacking is interesting but is composed of several subsequent lithography steps, which increases the chances of fabrication errors and is ultimately limited by the number of lithography steps one can afford.…”

“…Realization of thicker zone plates with similar resolution would require nanofabrication of structures with extremely high aspect ratios. As a consequence, other types of optics such as Kirkpatrick–Baez mirrors (KBM),21, 22 compound refractive lenses (CRL)23, 24, 25, 26 and multilayer‐Laue lenses (MLL)27, 28, 29, 30, 31 are mostly used in this energy range. High resolution KBMs require a complicated active wavefront correction scheme 22.…”

Calculated efficiencies of three-material low stress coatings for diffractive x-ray transmission optics

“…The transition layer thickness has been chosen according to the calculations of the stress free layer stack configurations in [11]. The results have been compared to some of the material combinations, which have been used for MLLs before, namely WSi 2 /Si, Mo/Si and MoSi 2 /Si [6,11,12]. The diffraction efficiencies were calculated for an MLL with the structure of a design with a focal length of 9.5 mm at an x-ray energy of 15 keV.…”

“…Further improvements can be achieved by tilting resulting in a part of the lens respecting the local Bragg condition significantly enhancing the local diffraction efficiency [5]. Furthermore big efforts have been made to manufacture a so-called wedged MLL, where all layers satisfy their respective local Bragg condition representing the current step in MLL development [6]. The off-axis geometry with no central beam stop prevents the apodization effect and enables a slight increase of the working distance compared to the full zone plate geometry [7].…”

Systematic efficiency study of line-doubled zone plates

“…High aspect ratio nano-structures can also be fabricated by other techniques like MACE (Metal Assisted Chemical Etching) in combination with line-doubling [14], multilayer lenses [15][16][17][18] or by stacking [19]. However, reaching the highest possible aspect ratio is not in the focus of this manuscript.…”