Neutron reflectometry investigates the nanoscale structure of surfaces and thin films at interface between materials. Specular neutron reflection probes the structure in the direction normal to the surface and reveals the atomic composition profile across an interface or thin film, which need not have an ordered in-plane structure. Neutron reflectometry has traditionally been used to study many different kinds of interfaces from soap films at the air-water interface to buried solid-liquid and liquid-liquid interfaces, with some of the key application areas being soft condensed matter and biomacromolecules. On the other hand, polarised neutron neutron reflectometry is sensitive to magnetic structures at interfaces, leading to many applications in functional materials. Off-specular neutron reflection or grazing incidence small angle scattering occur when the surface has a two dimensional structure, with neutron spin-echo encoding offering an additional tool to access larger length scales.
Reflectometry is represented by the following instruments in the ESS reference suite :
• Horizontal sample reflectometer - for free liquid surfaces, soft and biological materials
• Vertical sample reflectometer - for solid samples and advanced materials using polarised neutrons
• Surface scattering instrument - for studies of 2-3D surface structures