ATTAINMENT OF PHASE EQUILBRIUM IN MULTILAYERS

Structural, phase and chemical stabilities of multilayers Mo-Si, MOSi2- Si, W-Si, WSi2-Si, Cr-Sc, W-Sc, Mo-B4C, Mo−(B+C), Mo2B5-B4C, Cr3C2-C, TiC-C, Ti-Be and others were studied in 300-1100°C temperature range by small-angle and large-angle X-ray diffraction scattering and electron microscopy methods. The structural instability (crystallization of amorphous Si, C, MOSi2, WSi2, MoC, MoB2, Mo2B5, B and Cr3 C2 and recrystal-lization of polycrystal Mo, W, Sc, MoSi2, WSi2, Mo2B5 and MoC layers) as well as the phase instability (transformation of MoSi2 lattice from hexagonal to tetragonal modification) are responsible for the degradation of multilayers due to the development of the interface roughness and mechanical stresses. The chemical instability (formation of MoSi2 and WSi2 silicides at interfaces of Mo-Si and W-Si multilayers, Mo2C and MoC carbides and MoB2 and Mo2B5 borides in Mo-(B+C) multilayers, TiBe12 in Ti-Be ones) influences critically chemical composition profile, layer thicknesses and a period of multilayers. Formation of chemical compounds accompanied by an amorphization of polycrystal layers (growth of amorphous Mo2C and MoC carbides instead of polycrystal Mo at about 450 °C and the subsequent substitution of polycrystal molybdenum carbides on amorphous borides MoB2 and Mo2B5 at 700-800 °C in Mo-(B+C) multilayers) promotes the smoothening of interfaces. This effect of the chemical instability can be used for an improving of the X-ray reflectivity of multilayers.