Coatings for FEL optics: preparation and characterization of B4C and Pt
| Autor: | Jana Buchheim, Christian Horstmann, Grzegorz Gwalt, Michael Störmer, Frank Siewert |
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| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
030103 biophysics Nuclear and High Energy Physics Materials science Silicon chemistry.chemical_element coatings Substrate (electronics) engineering.material 01 natural sciences FEL optics 03 medical and health sciences Optics Coating FEL X ray mirrors Sputtering 0103 physical sciences Thin film X-ray mirrors 010306 general physics Reflectometry Instrumentation Radiation business.industry Photondiag2017 Workshop chemistry engineering business Layer (electronics) Surface finishing |
| Zdroj: | Journal of Synchrotron Radiation Störmer, M.; Siewert, F.; Horstmann, C.; Buchheim, J.; Gwalt, G.: Coatings for FEL optics: preparation and characterization of B4C and Pt. In: Journal of Synchrotron Radiation. Vol. 25 (2018) 1, 116-122. (DOI: /10.1107/S1600577517016095) |
| ISSN: | 1600-5775 |
| Popis: | Boron carbide and platinum are two suitable coating materials for X-ray mirrors at free-electron lasers worldwide. The achieved thickness uniformity for boron carbide is less than 1 nm peak-to-valley over 1500 mm mirror length. Large X-ray mirrors are required for beam transport at both present-day and future free-electron lasers (FELs) and synchrotron sources worldwide. The demand for large mirrors with lengths up to 1 m single layers consisting of light or heavy elements has increased during the last few decades. Accordingly, surface finishing technology is now able to produce large substrate lengths with micro-roughness on the sub-nanometer scale. At the Helmholtz-Zentrum Geesthacht (HZG), a 4.5 m-long sputtering facility enables us to deposit a desired single-layer material some tens of nanometers thick. For the European XFEL project, the shape error should be less than 2 nm over the whole 1 m X-ray mirror length to ensure the safe and efficient delivery of X-ray beams to the scientific instruments. The challenge is to achieve thin-film deposition on silicon substrates, benders and gratings without any change in mirror shape. Thin films of boron carbide and platinum with a thickness in the range 30–100 nm were manufactured using the HZG sputtering facility. This setup is able to cover areas of up to 1500 mm × 120 mm in one step using rectangular sputtering sources. The coatings produced were characterized using various thin-film methods. It was possible to improve the coating process to achieve a very high uniformity of the layer thickness. The movement of the substrate in front of the sputtering source has been optimized. A variation in B4C layer thickness below 1 nm (peak-to-valley) was achieved at a mean thickness of 51.8 nm over a deposition length of 1.5 m. In the case of Pt, reflectometry and micro-roughness measurements were performed. The uniformity in layer thickness was about 1 nm (peak-to-valley). The micro-roughness of the Pt layers showed no significant change in the coated state for layer thicknesses of 32 nm and 102 nm compared with the uncoated substrate state. The experimental results achieved will be discussed with regard to current restrictions and future developments. |
| Databáze: | OpenAIRE |
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