  Moving towards significantly smaller nanostructures, direct structuring
techniques such as electron beam lithography approach fundamental limitations
in feature size and aspect ratios. Application of nanostructures like
diffractive X-ray lenses requires feature sizes of below 10 nm to enter a new
regime in high resolution X-raymicroscopy. As such dimensions are difficult to
obtain using conventional electron beam lithography, we pursue a line-doubling
approach. We demonstrate that thismethod yields structure sizes as small as 6.4
nm. X-ray lenses fabricated in this way are tested for their efficiency and
microscopic resolution. In addition, the line-doubling technique is
successfully extended to a six-fold scheme, where each line in a template
structure written by electron beam lithography evolves into six metal lines.
