Hard X-ray projection imaging below 5 nm resolution

Abstract

High-resolution X-ray imaging of non-crystalline objects is often achieved through the approach of scanning coherent diffractive imaging known as ptychography. The imaging resolution is usually limited by the scattering properties of the sample, where weak diffraction signals at the highest scattering angles compete with background noise and parasitic scattering. Here we demonstrate that X-ray multilayer Laue lenses of high numerical aperture (NA) can be used to create a strong reference beam that holographically boosts that weak scattering from the sample over a large range of scattering angles, enabling high-resolution imaging that is tolerant to such noise. An imaging resolution of about 5 nm was achieved at a photon energy of 17.4 keV with lenses of 0.014 NA from a Siemens star test object and a sample of hierarchical nanoporous gold, recording projection holograms at a magnification of more than 30,000 directly on a pixel-array detector. A numerical study compared this approach to far-field ptychography, indicating significant advantages for using high-NA lenses in the presence of background noise. This imaging modality is particularly fast and efficient to record high-resolution transmission phase-contrast images over large fields of view in a facile manner.