  X-ray grating interferometry is an excellent technique for X-ray phase
contrast imaging and X-ray wavefront sensing with applications in materials
science, biology and medical diagnosis. Among other requirements, the method
depends on the availability of highly X-ray absorbing metallic gratings. Here,
we report on the fabrication and characterization of high aspect ratio iridium
gratings with a period of one micrometer and a depth of 30 micrometer combining
deep reactive ion etching of silicon and atomic layer deposition of iridium.
The implementation of such structures can greatly enhance the sensitivity of
grating-based X-ray phase contrast imaging and thus, expand further its broad
range of applications.
