Effects of interface roughness in a multilayer system on neutron reflectivity

The neutron reflectivity of a multilayer system with interface roughness is studied on the basis of the neutron optical method. The reduction of the specular reflection by the incoherent effect is taken into account by introducing imaginary phase factors in characteristic matrices. The modification of the optical potential by the coherent effect is considered by introducing an intermediate layer at each potential boundary, where the optical potential changes smoothly. Numerical calculation shows that the incoherent effect lowers the reflectivity on the whole, whereas the coherent effect reduces mainly the intensity of the second-or the higher-order Bragg peaks. It is found that these two effects explain experimental results reasonably well in cases of Ni/Ti multilayers.