Enhancement of diffraction efficiency of laminar-type diffraction gratings overcoated with diamond-like carbon (DLC) in soft x-ray region

Born is the critical trace element due to take the advantage of improving quenching characteristics in steel. Recently there is a great demand to detect the B-K emission band at around 6.76 nm more efficiently. To meet this demand we performed a feasibility study to enhance the diffraction efficiency of laminar-type diffraction grating based on a newly discovered physical phenomenon in the region of total reflection. The phenomenon is embodied as a transparent high-density material layer overcoated on a metal layer on grating grooves. The material should have intermediate diffractive index of vacuum and the metal layer. We found that high density diamond-like carbon (DLC) having a density of 3.1 g/cm3 is one of the best material and simulated the diffraction efficiency in a spectral region of 3.5-8.5 nm. The optimum thickness is 24 nm for an incidence angle of 87.0. Then the first order diffraction efficiency is expected to achieve up to 29.7 %, which is improved from 15.6 % for Ni or 14.1 % for Au, at 6.76 n