Suppression of corrugated boundaries in multilayer Fresnel zone plate for hard X-ray synchrotron radiation using cylindrical slit

Corrugated zone roughness of a circular Cu/Al multilayer Fresnel zone plate (FZP) was successfully suppressed. Such a zone corrugation was often observed in the concentric multilayers prepared using a conventional sputtering apparatus. The zone corrugation is a consequence of the oblique component of the deposition flux (i.e. shadowing effect). We therefore set a cylindrical slit (a linear slit on the surface of a stainless steel cylindrical shield) between the target and the substrate in order to eliminate the oblique flux. As a result, the zone corrugation was not observed using a scanning ion microscope (SIM).