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.