## 5 Conclusions  
In this work, the technological process for fabrication of two-dimensional X-ray gratings is described. The fabrication process is based on UV lithography and gold electroplating. Absorption gratings represented by periodic free-standing gold pillars with lateral structure sizes from 5 \(\upmu\)m to 25 \(\upmu\)m and heights from 5 \(\upmu\)m to 28 \(\upmu\)m have been manufactured. The gratings have shown a high degree of periodicity and defect-free patterns which enables their application for single-shot X-ray phase-contrast imaging. The gold height achieved in the manufacturing process absorbs more than 90% of X-ray radiation at the energy of 25 keV; for the transmission of 200-\(\upmu\)m-thick silicon substrate at this energy the WFM is about 0.8, which implies that the manufactured gratings can be used for single-shot imaging at energies up to 25 keV. An algorithm allowing the qualitative and quantitative characterization of homogeneity and uniformity of the micropattern over a large active area involved in the imaging measurement was developed. The simulated images include general effects like blurring, detector resolution limitations, noise, and misalignments. However, they do not include any information on local defects, such as the diffraction-induced shape distortion, overplating, pattern impurity, mask defects transferred to the final grating, etc. Such defects are becoming critical for small periods, like 10 \(\upmu\)m, as can be seen by comparing the real data histograms with the simulated data, while larger periods are less affected by the abovementioned defects and exhibit clear intensity modulation. From the evaluation of the grating structures in the radiographic setup, it follows that two-dimensional gratings with periods of 50 \(\upmu\)m and 25 \(\upmu\)m exhibit clear patterns and can be used for single-shot X-ray phase-contrast imaging at energies up to 25 keV. The gratings with 10 \(\upmu\)m period have multiple manufacturing-driven defects and require further quality improvement, for example, by using deep X-ray lithography or improved photoresist formulations. The evaluation of the grating quality will also be further improved, most probably introducing an image pattern recognition algorithm to be sensitive to small, localized defects. The findings reported in this paper can be used for the improvement of image quality and broadening of applications for X-ray phase-contrast single-shot imaging towards materials  
Figure 8: Real data absorption signal histogram decomposed into several Gaussian shape signals correlated to the different height of gold structures: (**a**) for a 10 \(\upmu\)m period grating (small Gaussians were treated as a local gold height inhomogeneity as their content in the entire profile was less than 2% each); and (**b**) for a 50 \(\upmu\)m period grating. In the legends, the percentage of the contribution to the signal was calculated from the areas of the Gaussians used for the approximation of the real data profiles. characterization and medical imaging. The developed algorithm could also provide additional information on the grating quality by utilizing single projection for easier data interpretation during measurements of various objects. This work was carried out with the support of the Karlsruhe Nano Micro Facility (KNMF), a Helmholtz Research Infrastructure at KIT; the Topo-Tomo beamline, located at the Karlsruhe synchrotron radiation facility of the KIT; the Karlsruhe School of Optics and Photonics (KSOP); and [PERSON] (IKP, KIT). [PERSON] and [PERSON] planned the technology development for the radiography experiments. [PERSON] fabricated the 2D gratings with the help of [PERSON]. [PERSON] tuned the negative photoresist to pattern the structures. [PERSON] contributed with ideas to optimize the structure development. [PERSON], [PERSON], and [PERSON] characterized the 2D gratings. [PERSON], [PERSON], and [PERSON] performed the experiments. [PERSON] and [PERSON] performed the data analysis.