Structural and thermal stability of B₄C/Ru multilayers with carbon barrier layers

Analysis of the chemical interaction between B₄C and Ru layers in multilayer structures depending on the thickness ratio (Γ) was carried out using X-ray photoelectron spectroscopy, X-ray diffraction and X-ray reflectometry. The results showed significant interlayer interaction with the formation of ruthenium borides, and it was found that an increase in the thickness of the B₄C layer (a decrease in the Γ parameter) leads to the appearance of borides of different stoichiometries. The introduction of a carbon barrier layer at the Ru-on-B₄C interface resulted in significant suppression of ruthenium boride formation. The thermal stability of the B₄C/Ru system was also studied upon annealing at 400 °C for 1 hour before and after the introduction of the carbon barrier layer. It was shown that the introduction of a carbon barrier layer at the Ru-on-B₄C interface increases the thermal stability of the system, which makes this system more suitable for use in optical systems exposed to long-term radiation. The obtained results are important for the development of highly efficient multilayer mirrors used in EUV lithography and X-ray optics.