NEUTRON REFLECTION FROM FACETED SURFACES

Diffuse scattering, often taken as evidence that a surface is rough on very small length scales, can also arise when neutrons (or X-rays) ar e reflected from a surface composed of many smooth facets. For a surfa ce composed of facets misoriented with respect to the average surface, the diffuse scattering displays a fringe at a wave vector transfer pe rpendicular to the surface that is equal to twice the critical wave ve ctor. The damping of the specular reflectivity does not follow the usu al Nevot-Croce form for such a faceted surface. A surface morphology o f this type can explain data we have obtained by reflecting neutrons f rom several different samples including one of polished silicon.