The broadband x-ray supermirrors have been designed, fabricated and studied experimentally. They are intended for operating in the photon energy range from 12.4 to 20keV at the fixed grazing incident angle of 0.5°. The choice of material pairs composing a non-periodic multilayer structure is considered from the maximum achievable reflectivity and the layer structure stability. Tungsten and silicon are selected, which have the great index contrast in this energy range and are suitable for fabrication with the use of the vested coating system. The interface width determined by transmission electron microscopy (TEM) lies in the range of 0.4~0.6nm. Following a theoretical approach including analytical and numerical techniques, the designed multilayer mirrors have a practically constant reflectivity of about 24% in the desired photon energy range. The multilayers were deposited onto polished silicon substrates by a high vacuum DC magnetron sputtering system and were characterized by x-ray diffractormeter (XRD) at 8.0keV. The experiments show that the sample has about 10% reflectivity in a wide angular range; The roughness of the interface for both tungsten on silicon layer and silicon on tungsten layer was estimated to be about 0.5nm. Oscillations in the reflectivity curve proved to be larger than the expected ones. They may be caused by the random variation of the layer thickness, as well as the interdiffusion between two materials. Possibilities for further improvements of wideband multilayer mirrors are analysed as well.

Date Published: 1 February 2006
PDF: 6 pages
Proc. SPIE 6034, ICO20: Optical Design and Fabrication, 603417 (1 February 2006); doi: 10.1117/12.668136

Published in SPIE Proceedings Vol. 6034:
ICO20: Optical Design and Fabrication
James Breckinridge; Yongtian Wang, Editor(s)