DFG-RSF: Beryllium based multilayer optics for the EUV spectral range

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At our synchrotron radiation facility BESSY-II recently a new At-Wavelength Metrology Station has been set into operation with which optical components for soft x-ray radiation can be measured at their design wavelength. This station incorporates our 20 years of expertise in soft x-ray optics and technology and it has a cutting-edge performance with respect to its measuring capabilities. The At-Wavelength characterization technique is indispensable in particular for multilayer optical elements of which the optical performance is strongly wavelength-dependent. Such information cannot be obtained by any other method. We want to use this facility to develop a novel kind of multilayer optics with promising performance in the range of EUV radiation and beyond. In this project we want to cooperate with one of the world's largest multilayer facility at the Institute for Physics of Microstructure in Nizhny Novgorod (IPM-RAS) with which we have cooperated successfully since more than two decades. This institute will produce Beryllium-containing multilayers (Al/Be, Ru/Be, Mo/Be, Mg/Be,...) applying various sputter- and ion-beam assisted techniques of atomic engineering to provide smooth layers and sharp interfaces with negligible interdiffusion. Laboratory techniques such as AFM, Cu k-alpha diffractometry etc. will be applied for standard performance tests, while their final performance is characterized with synchrotron radiation by At-Wavelength Metrology, Resonant Reflectivity and Reflection-NEXAFS at the absorption edges of the constituting atoms for depth-selected chemical and elemental analysis. There are many applications of such multilayer structures, which will exceed the performance of existing ones (Mo/Si), for instance for the next generation of EUV nanolithography or for solar astronomy. Our interest in such a multilayer optics is twofold: (1) We want to develop new Be-ML optics with high reflectivity for polarization steering and control. (2) Since we are able to manufacture high-precision blazed gratings, we want to apply a multilayer coating on top of a grating. The diffraction efficiency then can be increased considerably. After successful demonstration of the Be-multilayer performance a large grating is planned to be coated with such a novel multilayer and implemented into a beamline at BESSY II.