Effect of insertion of B4C at the interface Mo / Be depending on the film order

In the present work, formation of an interface region in the multilayer periodic Mo/Be mirrors was studied using X-ray photoelectron spectroscopy. The impact of a barrier B4C layer on the interdiffusion at both interfaces of the Mo/Be mirror (Mo-on-Be and Be-on-Mo) was analyzed in details paying particular attention to the interaction of the barrier B4C layer with the Mo and Be layers and accompanying oxidation processes. It was established that the barrier B4C layer: i) reduces the total amount of the beryllides at the interfaces, compensating by the appearance of MoB; ii) limits the formation of the Be-rich MoBeα beryllide at the Be-on-Mo interface making this interface more sharp; iii) facilitates the formation of beryllium carbide Be2C at both interfaces; iv) partially protects the oxidation of the beryllium layer located under the Mo layer. Additionally, theoretical analysis of probable interface reactions and their products was performed. The results obtained within the framework of the proposed models correlate well with the experimental data. Despite the simplicity of the suggested approach it exhibits satisfactory predictive power that can be exploited for materials selection to improve interface quality of multilayered structures.