Abstract

High performance normal incidence multilayer optics has been required for water-window wavelengths raging from 2.33 to 4.37 nm, at which soft x-ray microscope can be expected for living cells. Various fabrication studies have been reported with multilayer structures of W/Sc, W/B₄C, and so on. However, high reflectance enough to be practically used has not been obtained, because surface roughness, imperfections of interfaces and atomic-scale controllability of layer thickness are technical issues to be solved in these wavelengths. We have developed novel metal oxide multilayers with amorphous titanium oxide and aluminum oxide fabricated by atomic layer deposition technique, which can preferably prevent from making an alloy at the interface. This technique makes it possible to control the film thickness on an atomic scale due to self-limiting adsorption mechanism in surface chemical reactions.

© 1998 IEEE