X-ray holography using photoresists

We have recorded 56 nm resolution Gabor holograms of biological specimens using photoresist detectors and 1.8-3.6 nm x-rays from an undulator source. With this technique, we are able to obtain high image resolution without the use of x-ray lenses; the resolution limit of the photoresist PMMA is thought to be in the 5-10 nm range. The technique also makes good use of partially coherent or multimode sources; monochromaticity requirements are eased compared to longer focal length zone-plate based scanning x-ray microscopes, and multiple spatially coherent modes can be used to record a hologram of a large field (although the image resolution will be limited by the width of one mode). Since the image is focussed in the reconstruction stage, the specimen alignment requirements are non-demanding. Judging from the survivability of photoresist exposures obtained using laser plasma x-ray sources, our current scheme may be compatible with flash exposures with x-ray lasers as they become available.