X-ray zone plates fabricated using electron beam lithography and reactive ion etching

A Fresnel zone plate, a focusing element that operates using diffraction, is a promising candidate for x-ray optical elements since the index of refraction of all materials in this region is slightly less than unity. In this report, a new fabrication method for zone plates using electron beam lithography and reactive ion etching is described. By this method, it is possible to obtain a high resolution zone plate with a large aspect ratio. Focusing characteristics of fabricated zone plates are measured by synchrotron radiation. At the wavelength of 9 nm, the spot size of 2 μm is obtained at the focal point of 100 mm.