Development of MoSi2/Si lamellar multilayer grating for the narrowband soft x-ray monochromator

Abstract

Multilayer mirrors (MLM) with narrow spectral bandwidth are important for X-ray spectroscopy and imaging experiments in order to improve the spectral resolution. To overcome the bandwidth limit of conventional multilayers, single order lamellar multilayer grating (LMG) is one of the most promising methods. Driven by the high resolution spectroscopy for the plasma diagnosis at E=~1keV, single order LMG based on MoSi2/Si multilayer is developed. The multilayer period is 5.0 nm, with the Si thickness ratio of 0.6. An LMG with 600 nm grating period and 1:2 line-to-space ratio is designed. As it works at the single order diffraction regime, the 0th order peak reflectance (in theory) of the LMG is 45.4% at E=1.2 keV, which is the same as the multilayer mirror. The bandwidth can be reduced by 3 times compared to the planar multilayer. To demonstrate this LMG structure, MoSi2/Si multilayers have been deposited using direct current magnetron sputtering. Deep reactive ion etching technique is under optimization in order to produce the multilayer grating structure with a high aspect-ratio of around 5.