FIB diamond micromachining for X-ray applications
- Ms. Polina MEDVEDSKAYA
- Ms. Polina MEDVEDSKAYA (Immanuel Kant Baltic Federal University)
The high degree of coherence, brightness and power of X-radiation from free-electron X-ray lasers (XFELs) and 4-generation synchrotron sources  requires the development of new X-ray optics capable of withstanding extreme thermal and radiation loads. Diamond has excellent optical properties for these X-ray sources: high temperature stability and chemical inertness, relatively low absorption of hard X-rays, high thermal conductivity and low coefficient of thermal expansion. Due to its high strength and hardness, the diamond cannot be easily subjected to direct mechanical or chemical machining. Therefore, laser ablation is one of the most suitable methods for manufacturing diamond X-ray refractive optics [2-3]. However, the main disadvantage of this method is the relatively high roughness of the diamond optical surface (Ra ≈ 0.3 μm). It is necessary to reduce the roughness of the optical elements with high precision for obtaining a high-quality X-ray lenses. The focused ion beam (FIB) method is the best candidate for solving this problem due to its possibility of physically spraying any materials on the micro- and nanoscale .
In this work, we present a new approach for final polishing of the diamond surface of refractive lenses by ion beam lithography method. Currently, ion lithography is widely used for the modification and fabrication of new X-ray optical elements [5, 6]. We demonstrate the new results of smoothing two-dimensional parabolic refractive lens surface by the dual-beam system ZEISS Crossbeam 540. This approach has enabled us to reduce the roughness of the diamond single crystal refractive lens with 1mm aperture and 200 um radius of curvature. The obtained results are very promising and we hope that the diamond optics will be applicable to the tasks of high-resolution microscopy on the extremely bright sources.
Acknowledgments This research was supported by Ministry of Education and Science of the Russian Federation (contract № 14.Y26.31.0002, 16.4119.2017/PCh).
 M. Borland, Progress Toward an Ultimate Storage Ring Light Source, Journal of Physics: Conference Series, 425 (2013) 0420 16.
 M. Polikarpov, I. Snigireva, J. Morse, V. Yunkin, S. Kuznetsov, A. Snigirev, Large-acceptance diamond planar refractive lenses manufactured by laser cutting, J Synchrotron Radiat, 22 (2015) 23-28.
 M. Polikarpov, I. Snigireva, A. Snigirev, Focusing of white synchrotron radiation using large-acceptance cylindrical refractive lenses made of single – crystal diamond, AIP Conference Proceedings, 1741 (2016) 040024.
 Song, In-Hyouk, Yves-Alain Peter, and Michel Meunier. "Smoothing dry-etched microstructure sidewalls using focused ion beam milling for optical applications." Journal of micromechanics and microengineering 17.8 (2007): 1593.
Falch K. V. et al. In situ hard X-ray transmission microscopy for material science //Journal of Materials Science. 2017. Т. 52. №. 6. С. 3497-3507.
 Gissibl T. et al. Two-photon direct laser writing of ultracompact multi-lens objectives // Nature Photonics. 2016. Т. 10. №. 8. С. 554.