LAUSR

Increasing the focusing capability of hard X-ray zone plates would enable many exciting discoveries in diverse scientific and technological fields, including drug design, nanotechnology, battery membranes, and supercapacitors. However, hard X-ray microscopy and tomography with Fresnel zone plates (FZPs) are limited in resolution to ~25 nm. High energy X-rays offer increased penetration depth and allow excitation in K-absorption edges of medium-heavy elements and in L and M absorption edges of heavy elements for chemical analysis. Currently, synchrotron radiation facilities are pursuing upgrades to increase the coherence and brilliance of their beam line sources, to create conditions for sub-20 nm focusing. These conditions put a tremendous demand on fabrication of adequate FZPs, requiring Fresnel zones of few nm width and few m height, with aspect ratios of 100:1 to 1000:1. For such aspect ratios, traditional top-down fabrication processes such as lithography and etching or electroforming are far beyond their limits. Bottom-up techniques such as sequential sputtering [1] or sequential atomic layer deposition onto wires [2] or into capillary lumens [3], followed by slicing have been proposed but of limited utility due to zone distortions or slicing difficulties. Here, we demonstrate a fabrication method capable of batch producing hard X-ray zone plates to form hundreds of device chips out of a single Si wafer. These zone plates show extraordinary potential to serve as hard X-ray zone plates for the focusing of X-rays to 5 nm and beyond.