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Nanomachining with subsequent polishing of the active surfaces of crystal X-ray optics
The high-asymmetry diffraction producing beam magnification/compression in the grazing incidence/emergence mode requires a high quality of the crystal surface [1]. We have applied advanced nanomachining using Single Point Diamond Turning (SPDT) to prepare the crystal surfaces. It allows to obtain high shape accuracy, however the surface roughness and subsurface defects are usually several times higher than the value achieved by chemo-mechanical in planar semiconductor technology.
Subsequent to the SPDT several finishing methods, including conventional mechanical lapping, chemical polishing, and chemo-mechanical polishing, have been tested. We have obtained the surface roughness (RMS) of ∼0.3 nm and an absence of the subsurface damages [2] using a fine polishing 15-min process with a polishing solution containing SiO2 nanoparticles (20 nm). Reciprocal space mapping by high resolution X-ray diffractometry showed suppression of the so-called undesirable surface grating truncation rods.
These results were achieved in collaboration with IP SAS, international cooperation with DESY Hamburg, MU Brno, IMEM CNR Parma and within the EU and national projects and are highly rated by several subscribers of the results.
Comparison of RMS (root mean squared) roughness of germanium surfaces prepared by nano-machining and 5, 10 and 15 min post-polishing process using colloidal solutions containing SiO2 and Al2O3 nanoparticles.
Zápražný, Z., Korytár, D., Jergel, M., Šiffalovič, P., Dobročka, E., Vagovič, P., Ferrari, C., Mikulík, P., Demydenko, M., Mikloška, M., : Calculations and surface quality measurements of high-asymmetry angle x-ray crystal monochromators for advanced x-ray imaging and metrological applications. Optical Engn. 54 (2015) 035101.
Zápražný, Z., Korytár, D., Jergel, M., Šiffalovič, P., Halahovets, Y., Keckes, J., Maťko, I., Ferrari C., Vagovič, P., Mikloška, M.: Nano-machining For Advanced X-ray Crystal Optics. AIP conf. Proc. Submitted, (2016).