## Abstract

We studied the structure and optical properties of ${\mathrm{B}}_{4}\mathrm{C}/\mathrm{Mo}/\mathrm{Y}/\mathrm{Si}$ multilayer systems. Using extended x-ray absorption fine structure measurements at the Y and Mo K-edge, the structure of the subnanometer thick Y layer and the underlying Mo layer were analyzed. It was found that even a 0.2 nm thick Y layer significantly reduced silicon diffusion toward Mo, thus reducing Mo silicide formation. Hard x-ray reflectometry showed that the difference in average interface roughness of the ${\mathrm{B}}_{4}\mathrm{C}/\mathrm{Mo}/\mathrm{Y}/\mathrm{Si}$ multilayer structure compared to Mo/Si and ${\mathrm{B}}_{4}\mathrm{C}/\mathrm{Mo}/{\mathrm{B}}_{4}\mathrm{C}/\mathrm{Si}$ multilayer structures was negligible. Soft x-ray reflectometry showed optical improvement of ${\mathrm{B}}_{4}\mathrm{C}/\mathrm{Mo}/\mathrm{Y}/\mathrm{Si}$ with respect to Mo/Si and ${\mathrm{B}}_{4}\mathrm{C}/\mathrm{Mo}/{\mathrm{B}}_{4}\mathrm{C}/\mathrm{Si}$ multilayer structures.

© 2012 Optical Society of America

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