Smoothing of interfaces in ultrathin Mo/Si multilayers by ion bombardment

Abstract

Mo/Si multilayers with a bilayer thickness of 2.6 nm are produced by electron beam evaporation in ultrahigh vacuum for soft X-ray optical applications. High reflectivities resulting from constructive interference in the stack are limited by the optical constants of the materials and by the quality of the interfaces. Smoothing of the boundaries is obtained by bombardment of the deposited layers with Ar + ions. The smoothness of the interfaces is controlled during the deposition by in situ measurement of the reflectivity for the C K radiation of the stack and after completion of the stack by means of a grazing X-ray reflection set-up with Cu Kα radiation. The soft X-ray reflectivity is measured with a laser-induced plasma light source.