Effect of the nitro­gen content of sputtering gas during Ni deposition on Ni/Ti periodic multilayers and neutron supermirror performance

Neutron supermirrors are indispensable in neutron research devices. Their performance has been improved using reactive magnetron sputtering. This study investigates the effects of nitro­gen content in a mixed sputtering gas during Ni deposition. Ni/Ti periodic multilayers with different d spacings and neutron supermirrors with m = 3 were prepared under different nitro­gen partial pressures. Comparison of samples prepared under two different nitro­gen contents (12 and 20%) showed that the interfacial roughness and the internal stresses of the periodic multilayer films with 20% nitro­gen were smaller, the interface diffusion of the supermirrors with 20% nitro­gen decreased, and the interface became clearer and more organized. Furthermore, the neutron reflectivity of the Ni/Ti supermirrors deposited under 20% nitro­gen was 0.89 at m = 3.05.