Experimental evaluation of enhancement of diffraction efficiency by overcoating diamond-like carbon (DLC) on soft X-ray laminar-type gratings

Imazono, Takashi; Koike, Masato; Nagano, Tetsuya*; Sasai, Hiroyuki*; Oue, Yuki*; Kuramoto, Satoshi*; Terauchi, Masami*; Takahashi, Hideyuki*; Notoya, Satoshi*; Murano, Takanori*; Gullikson, E. M.*

We have experimentally found that the diffraction efficiency of a Ni-coated grating can be improved by merely overcoating a high-density carbon film, i.e., diamond-like carbon (DLC), on the grating. The thickness of Ni and DLC layers were 30 nm and 23 nm, respectively. The diffraction efficiencies of the Ni grating with DLC overcoating was measured to be 26.9% at 6.76 nm at an incident angle of 87.07, which is about 90% of a simulation value of 29.7% and exceeds the measured efficiencies of the reference gratings, i.e., 16.9% for the Ni grating and 12.5% for the Au grating. This is the first experimental results of the enhancement of the diffraction efficiency by overcoating with a DLC on a conventional grating.