Medium Energy Ion Scattering

The Medium Energy Ion Scattering (MEIS) facility provides an instrument for materials characterisation that is accessible to industry and academia, separately or in collaboration.  The instrument is unique worldwide, being the only one of its kind to operate as a user facility. It thus offers an outstanding capability to UK researchers for the investigation of surface and near-surface phenomena using a technique that is sensitive to both the composition and structure of materials, with a depth resolution down to single atomic layer spacing. 

The ability to characterize materials in terms of their composition and structure with virtually monolayer resolution makes MEIS an ideal technique for the characterisation of surfaces, thin films and nanostructures. This has led to its application over a wide range of industrially important materials including catalysts, magnetic materials, metal alloys and semiconductors. Technologies to which MEIS has contributed include, high dielectric constant films for processor chips, GMR read/write heads for hard disc drives and corrosion protection for light alloys used in construction and transport.

 

Further Information

Medium energy (50 – 250 keV) beams of light ions (usually H⁺ or He⁺) are used to probe the surface and near surface region. The beam is incident on a sample target along a known direction and the energy and angle of the scattered ions are measured simultaneously using an electrostatic analyser with two-dimensional detector. Simple ‘billiard-ball’ mechanics determines the atomic mass of components of the target, whilst depth sensitivity arises due to the more subtle energy losses that occur as an ion passes through a solid. Structure determination is via the variation in scattered ion intensity that arises due to shadowing and blocking of the ions by atoms in the target along specific crystallographic directions.