Evolution of Structure,Phase Composition,and X-Ray Reflectivity of Multilayer Mirrors Mo–(B + C) after Annealing at 250–1100°C

Structural, phase, and chemical stabilities of x-ray multilayer mirrors Mo–(B + C) with periods in the range 8–11.5 nm were studied at temperatures of 250–1100°C by small-angle and large-angle x-ray diffraction and electron microscopy methods. Two amorphizations at ~450 and ~750°C and two crystallizations at ~650 and ~850°C of Mo-based layers were observed, which were due to the formation of the molybdenum carbides MoC (hex), γ-MoC, and Mo₂C instead of the metal Mo, and to the formation of the molybdenum borides MoB₂ and Mo₂B₅ instead of molybdenum carbides, respectively. Both amorphizations of Mo-based layers were accompanied by smoothing of interfaces and by an increase of the multilayer x-ray reflectivity at λ = 0.154 nm. Both crystallizations of Mo-based layers promoted the development of interface roughness and a decrease of multilayer x-ray reflectivity. The destruction of Mo–(B + C) multilayers at ~ 1100°C was caused by the recrystallization of Mo₂B₅ layers.