Development of spin-contrast-variation neutron reflectometry for structural analysis of multilayer films*

The spin-contrast-variation neutron reflectometry technique was developed for the structural analysis of multilayer films. Polarized-neutron reflectivity curves of film samples vary according to their proton polarization (P_H). The P_H-dependent reflectivity curves of a polystyrene monolayer film were precisely reproduced using a common set of structural parameters and the P_H-dependent neutron scattering length density of polystyrene, ensuring that these curves are not deformed by inhomogeneous P_H but can be used for structural analysis. Unpolarized reflectivity curves of poly(styrene-block-isoprene) films were reproduced a lot of models. The global fit of the P_H-dependent multiple reflectivity curves severely restrict the models. In this manner, the spin-contrast-variation neutron reflectometry technique determines the structure of multiple surfaces and interfaces of film samples while excluding the incorrect structure that accidentally accounts for a single unpolarized reflectivity curve only.