Fabrication and Characterization of High Aspect Ratio Hard X-ray Zone Plates with Ultrananocrystalline Diamond Molds

Hard x-ray zone plate development has played an important role in improving x-ray microscopy through finer resolution and greater functional X-ray energy. Similar to circular diffraction gratings except with changing period as a function of radius, zone plates are diffractive focusing optics with resolution determined by the outer most zone width (OZW). Hard X-ray zone plates are mostly phase zone plates with a limited efficiency that peaks when the zone material causes a 7E-phase shift on the x-ray, and the zone thickness required can be multiple microns dependent on x-ray energy. The combination of sub-100-nm resolution and peak efficiency for hard x-rays requires very high aspect ratio zones. In this dissertation, two materials were used to fabricate high aspect ratio zone plates in a single layer mold and a two layer mold process.;Ultrananocrystalline diamond (UNCD) is composed of 2-5 nm diamond grains bounded together with graphitic bonds. This form of diamond can be deposited onto substrates with thickness greater than a micron and with physical properties similar to bulk diamond. Hydrogen silsesquioxane (HSQ) is a spin on glass that is also a high contrast electron beam lithography resist. A thick layer of HSQ can be patterned into high aspect ratio structures and could be used as a pattern transfer mask for several etch recipes. Both of these materials were used to fabricate up to 25 aspect ratio zone plates and with OZW of 60 and 80 nm. Zone plates fabricated with UNCD were the first high aspect ratio zone plates using a diamond like material and this technique was leveraged into a new fabrication method using two layers as an electroplating mold. Fabricated zone plates were characterized to measure the optical properties to compare with the fabrication properties. After characterization, several zone plate models based on fabricated zone plates were developed and simulated using a wave propagation technique to compare with the characterization data. The results from fabrication, characterization, and simulation of zone plates with 25 aspect ratio will be presented as well as future possibilities for the techniques used.