Ion bombardment effects on nucleation of sputtered Mo nano-crystals in Mo/B4C/Si multilayers

Over recent years, the introduction of Mo/Si multilayers mirrors with different barrier layers for the interfaces has allowed increasing mirror reflectance, life and temperature stability. The effects of these very thin barrier layers on multilayer growth, such as interlayer formation and Mo crystallization, are not completely understood and deserve further study. This work shows, by using XRD and TEM analysis, that the crystallization thickness of the sputtered deposited Mo layers, when the boron carbide interlayer is present, increases from 2.0 nm to about 2.6 nm with respect to conventional Mo/Si multilayers. Furthermore some effects of ion energy bombardment on the nano-crystals formation and interlayer structure evolution have also been studied, showing an increase of preferential orientation for higher ion energies.