First tantalum zone plates for the TWINMIC X-ray microscope project

Abstract

We report the fabrication of X-ray zone plates made of tantalum, designed for use in the TWINMIC microscope project at photon energies between 0.25 and 2.5 keV. The zone plates have an outermost zone width of 80 nm, Ta thicknesses between 200 and 300 nm, and diameters between 250 and 500 μm. Tantalum layers were sputtered onto silicon nitride membranes. The zone-plate pattern was generated with electron-beam lithography at an electron energy of 2.5 keV, and transferred into tantalum by reactive ion etching. Central stops were deposited on some zone plates. Performance tests at the European synchrotron radiation facility (ESRF) with 2.5-keV X rays show that the spatial resolution of the zone plates is 100 nm or better when used in a scanning microscopy system.