Full-field hard x-ray microscopy below 30 nm: a challenging nanofabrication achievement.

The fabrication of devices to focus hard x-rays is one of the most difficult—and important—challenges in nanotechnology. Here we show that Fresnel zone plates combining 30 nm external zones and a high aspect ratio finally bring hard x-ray microscopy beyond the 30 nm Rayleigh spatial resolution level and measurable spatial frequencies down to 20–23 nm feature size. After presenting the overall nanofabrication process and the characterization test results, we discuss the potential research impact of these resolution levels.