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Total-reflection high-energy positron diffraction (TRHEPD) for structure determination of the topmost and immediate sub-surface atomic layers

Total-reflection high-energy positron diffraction (TRHEPD) has recently been developed to investigate the surface structure (atomic geometry) and surface properties of materials. It is the positron (the antiparticle of the electron) counterpart of reflection high-energy electron diffraction (RHEED). Depending on the glancing angle of incidence, positrons are totally reflected from the surface or shallowly penetrate into the bulk of the sample solid. Thus, it is possible to obtain information about the topmost and immediate sub-surface layers without the background effect of the bulk. In this review, this distinctive feature of the TRHEPD process and some of the results on surface structures and characteristics are described.