Nanofabrication of tungsten zone plates with integrated platinum central stop for hard X-ray applications

• Nanofabrication of tungsten zone plates for hard X-rays.
• Combining zone plate optic and platinum central stop to simplify experimental arrangements.
• Zone plate characterization in terms of ptychography at 8 keV is presented.
• Diffraction-limited focus spot size of 53 nm diameter.

We present a nanofabrication process for producing tungsten zone plates used in hard X-ray applications including a method of integrating a high-energy absorbing central stop with the optic. Tungsten zone plates are structured with electron-beam lithography and subsequent reactive ion etching. The central stop originates from a platinum wire. It is cut to dimension by focused ion beam etching, and afterwards attached to the zone plate center using ion beam induced deposition of platinum. A zone plate with integrated central stop will simplify alignment in hard X-ray scanning microscope arrangements where the 0th order light must be eliminated. The focusing performance of the zone plate device was investigated by scanning coherent diffraction imaging (ptychography) at 8 keV photon energy. We could demonstrate a diffraction-limited focus size of 53 nm diameter full-width-at-half-maximum. Tungsten zone plates with integrated central stops show promising results for use in hard X-ray microscopes at high-brightness facilities.

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