Resolution in x-ray microscopes

Abstract

X-ray microscopes can be roughly grouped into two categories: soft x-ray microscopes (λ ≈ 1-10 nm) which are able to image specimens at up to 30 nm resolution with some elemental mapping capabilities, and hard x-ray microprobes (E ≈ 3-100 keV) which are able to map trace chemical compositions and produce tomograms at ∼ 2 μm resolution. In both cases, the sample can be hydrated and in air, its thickness can be range from a few μm (with soft x rays) to a few mm (hard x rays), and the radiation dose delivered is considerably lower than what is involved in the equivalent electron microscopy technique.Some x-ray microscopes are lensless instruments. In contact microscopy and Gabor holography, soft x rays passing through the sample are recorded directly on high resolution photoresists (e.g., PMMA). Shinozaki et al. have studied the x-ray exposure properties of PMMA in detail, and have concluded that a detector resolution limit of 20 nm or better should be attainable.