Structure analysis of a buried interface between organic and porous inorganic layers using spin-contrast-variation neutron reflectivity

This work demonstrates the advantage of spin-contrast-variation neutron reflectivity (NR) for the structure analysis of a buried interface in a bilayer film comprising organic and inorganic layers of acrylic urethane resin and methylated silica (MePDS), derived from methyl-group-substituted perhydropolysilazane. As the proton polarization P-H changed from 0 to +/- 24%, the NR curve of the bilayer film varied significantly. These NR curves were not reproduced using global fitting with a standard bilayer model. The oscillation in the NR curve at P-H = -24% was shifted slightly and non-negligibly from the fitting curve using the best-fit structure parameters for the curve at P-H = 0%. It was found from the shift of the oscillation that the density of the MePDS layer decreased within several nanometres of the interface, but the resin did not permeate the low-density MePDS layer.