The role of ultra-thin carbon barrier layers for fabrication of La/B4C interferential mirrors: Study by time-of-flight secondary ion mass spectrometry and high-resolution transmission electron microscopy

Time-of-flight secondary ion mass spectrometry and high-resolution transmission electron microscopy study is reported on depth profiling of 375 nm-thick multilayer La/B4C interferential mirrors produced by magnetron sputtering for X-ray radiation at the wavelength of 6.7 nm. The introduction of ultra-thin (0.5 nm) carbon barrier layer inside each period of ca. 7.5 nm suppressed the broadening of interface regions, decreased the width of La and B profiles and as a result improved the reflectance of mirrors. Depending on the layers' sequence (La/C/B4C or La/B4C/C upward the Si substrate), two different mechanisms-chemical interaction and reaction diffusion, were employed for qualitative explanation of the obtained results. (C) 2015 Elsevier B.V. All rights reserved.