High efficiency diffraction grating overcoated with oxide film for 5-20nm region

Koike, Masato; Nagano, Tetsuya*

Boron (B) in the steel material can greatly contribute to the improvement of the quenching property by the addition in a few tens ppm level. Taking this advantage the automotive steel sheets becomes possible lighter remains maintained strength. However, in the steelmaking process, accurate control of the B addition quantity in ppm level is needed. Also there is a strong demand for detailed electronic structure analysis for boron compounds. The authors have found a unique method based on a new physical phenomenon, which can dramatically increase the diffraction efficiency of the laminar type diffraction grating coated with a metal single-layer film such as gold around B-K emission line (6.76 nm). This phenomenon, in the grazing incidence area where causes the total reflection, can be appeared by overcoating with a transparent and high density layer having a certain thickness on the metal coated grating grooves. For the overcoating layer, it is desirable to have an intermediate refractive index in vacuum and the metal layer. From this standpoint we did a search on the oxide films which are generally used as optical coating. Consequently, TiO, CeO, etc., were found to be promising candidates to meet this criterion. The results of numerical calculation shows that the diffraction efficiency of both TiO and CeO is 22% at 6.76 nm and it is a significant improvement from 15.6% and 14.1% for Ni and Au, respectively.