Structural analysis of a Mo/Si multilayered x-ray mirror by x-ray diffraction

Abstract

A molybdenum-silicon multilayer structure for use as a soft x-ray mirror has been fabricated using a magnetron sputtering system and studied through XRD (X-ray diffraction) of Cu K-alpha (1.54 Angstrom) radiation. The angular positions, the relative intensities, the widths of the Bragg primary and secondary peaks in the XRD pattern are sensitive to structural parameters such as the unit thickness (bilayer thickness), the thickness ratio of composite materials, the degrees of interdiffusion and the roughness at the interfaces. The effects of each structural parameter on the XRD pattern have been investigated. The results show that the angular positions of the Bragg primary peaks are sensitive to the bilayer thickness and that the pattern of the secondary peaks around the low-order Bragg primary peaks are sensitive to the thickness ratio. It is also found that the major effect of interfacial diffusion is the reduction of the intensities of the high-order Bragg primary peaks and that the roughness is responsible for the broadening of the widths of the Bragg primary peaks and the increase of the intensities of the Bragg secondary peaks relative to those of the primary ones. The above results were applied to analyze experimental XRD data to draw the structural parameters of a molybdenum-silicon multilayer soft X-ray mirror.