Substantial improvements in the nanofabrication and characteristics of gold Fresnel zone plates yielded unprecedented resolution levels in hard-x-ray microscopy. Tests performed on a variety of specimens with 8–10keV photons demonstrated a first-order lateral resolution below 40nm based on the Rayleigh criterion. Combined with the use of a phase contrast technique, this makes it possible to view features in the 30nm range; good-quality images can be obtained at video rate, down to 50ms∕frame. The important repercussions on materials science, nanotechnology, and the life sciences are discussed.

The technology to focus hard-X-rays (photon energy larger than 1–2 keV) has made great progress in the past three years. The progress was particularly spectacular for lenses based on the Fresnel zone plate concept. The spatial resolution notably increased by a factor of three, opening up entirely new domains of application, specifically in biomedical research. As we shall see, this evolution is the result of a painstaking optimization of many different aspects rather than of a single technical breakthrough.

A nanofabrication approach based on advanced e-beam lithography and electrodeposition successfully produced high-resolution (≈40 nm line width) metal structures with high aspect ratio (>12) and high density. The combination of these characteristics is essential for hard-x-ray optical components such as zone plates, for x-ray lithography masks and for other devices.