X-ray holographic microscopy using photoresists

Gabor x-ray holograms of biological specimens and of test objects that display <56-nm resolution are presented. This spatial resolution is more than an order of magnitude smaller than what has been achieved previously in x-ray holography. The holograms were recorded on photoresist using 2.57-nm soft x rays from the X-17t undulator at the National Syncrotron Light Source at Brookhaven National Laboratory. The processed photoresists were enlarged with an electron microscope and digitized using a scanning microdensitometer; the digitized holograms were reconstructed numerically. The exposure requirements were in good agreement with simple theory. The method offers promise as a technique for soft-x-ray microscopy.