What Can we Learn from off-Specular Neutron Reflection?

Abstract

ABSTRACTThis paper provides a brief introduction to the subject of off-specular neutron scattering by rough interfaces. Such scattering can be calculated using the distorted-wave Born approximation (DWBA) in which the neutron wavefunctions for a system with smooth interfaces are used as the basis for perturbation theory. Although it has been applied successfully to model the scattering from rough surfaces, the DWBA has several quantitative and qualitative limitations, some of which are described in this paper. When it is applied to multilayer systems, the DWBA correctly predicts a number of qualitative features of the diffuse scattering, including fringes of scattering that result from correlations between the roughnesses of neighbouring interfaces. A remarkable feature of diffuse neutron reflection is the range of length scales within a surface or interface that is probed. This is illustrated here by data obtained with a self-assembled multilayer of organic molecules where distances between 500 Å and 3 μm parallel to the layers are probed.