Study of the Reflectivity and Microstructure of Mo/Be Multilayer Mirrors

The reflection coefficient and microstructure of Mo/Be multilayer mirrors are studied as functions of Gamma, i.e., the ratio of the Mo-layer thickness to the period dp. The thickness and period of the layers are studied using X-ray diffraction (wavelength 0.154 nm). Clearly defined high-intensity Bragg-reflection peaks indicate good reproducibility of the layer thicknesses over the depth of the multilayer structure and the high quality of interfaces. The reflectivity of the mirror at a wavelength of 11.4 nm is maximum 62% at Gamma = 0.42. It sharply decreases at higher and lower values of Gamma. Both Mo and Be layers at Gamma = 0.42 are polycrystals, which are studied using X-ray diffraction and Raman spectroscopy, respectively. It is also found that the sizes of crystallites almost coincide with the thicknesses of Be and Mo layers in the period.