The thin film deposition technology for fabrication of the mirror optics for the Advanced Telescope for HighEnergy Astrophysics (ATHENA) has been established. Numerous coating process parameters impact the quality of the thin films. Defining a margin within the coating process parameter space, where the deposited thin film performs similar in X-ray reflectivity is key to avoid unforeseen risks within the coating process for the ATHENA flight optics production. In this work, we investigate the coating process parameter influence on the thin film properties with a focus on micro roughness, deposition rate and residual film stress when deposited under various process conditions. The thin films were produced by varying the following three coating process parameters: discharge power, discharge voltage and working gas pressure. The thin films were characterized using X–ray reflectometry at 3.4–10.0 keV. A main result of this work is that the residual stress of single layer iridium and boron carbide films can be reduced by a factor of approximately two, by increasing the working gas pressure while maintaining a high film quality.
The thin film coating technology for the European Space Agency mission, Advanced Telescope for High-Energy Astrophysics (Athena) has been established. The X-ray optics of the Athena telescope is based on Silicon Pore Optics (SPO) technology which is enhanced by the thin film coatings deposited on the reflective surface of the SPO plates. In this work, we present a literature study of the coating process parameter space and provide an overview of the thin film properties with a focus on micro roughness, chemical composition and wear resistance when deposited under various process conditions. We determined, that the thin film density depends strongly on the mobility of the adatoms on the substrate surface. Some coating process parameters, which have a significant impact on the adatom mobility are the discharge voltage, the working gas pressure and the substrate temperature.
We present the latest progress on the industrial scale coating facility for the Advanced Telescope for High-ENergy Astrophysics (ATHENA) mission. The facility has been successfully commissioned and tested, completing an important milestone in preparation of the Silicon Pore Optics (SPO) production capability. We qualified the coating facility by depositing iridium and boron carbide thin films in different configurations under various process conditions including pre-coating in-system plasma cleaning. The thin films were characterized with X-Ray Reectometry (XRR) using laboratory X-ray sources Cu K-α at 8.048 keV and PTB's four-crystal monochromator beamline at the synchrotron radiation facility BESSY II in the energy range from 3.6 keV to 10.0 keV. Additional X-ray Photoelectron Spectroscopy (XPS) measurements were performed with Al K-α radiation to analyze the composition of the deposited thin films.
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