The microstructure of transition boundaries in multilayer Mo/Be systems

The microstructure of the Mo/Be multilayer periodic system has been investigated using the methods of reflectometry, diffractometry, and EXAFS spectroscopy. It is found that, in the Mo/Be system, a mixed zone with different compositions are formed at the interfaces. On the Mo-on-Be and Be-on-Mo interfaces, mixed zones with a composition similar to МоВе$_{22}$ and МоВе$_2$ are formed, respectively. After thermal annealing for 1 h, the structure of transition interfaces in the multilayer system remains stable. Upon further annealing, diffusion processes occur, leading to the formation of the other compound (МоВе$_2$ instead of МоВе$_{22}$); however, the period of the structure remains unchanged. Such a behavior explains the increase in the reflectance of Mo/Be mirrors after 1-h annealing and its subsequent decrease for a longer annealing time.