Positrons in Surface Physics

TL;DR

This paper reviews recent advances in surface physics using positron beams, highlighting techniques like RHEPD and PAES that provide high-precision surface analysis and elemental detection.

Contribution

It introduces novel positron-based methods for surface analysis, emphasizing their unique advantages and recent developments in the field.

Findings

RHEPD enables atom-level surface structure determination.

PAES offers layer-specific elemental analysis with minimal background.

Low-energy spin-polarized positrons probe surface electron polarization.

Abstract

Within the last decade powerful methods have been developed to study surfaces using bright low-energy positron beams. These novel analysis tools exploit the unique properties of positron interaction with surfaces, which comprise the absence of exchange interaction, repulsive crystal potential and positron trapping in delocalized surface states at low energies. By applying reflection high-energy positron diffraction (RHEPD) one can benefit from the phenomenon of total reflection below a critical angle that is not present in electron surface diffraction. Therefore, RHEPD allows the determination of the atom positions of (reconstructed) surfaces with outstanding accuracy. The main advantages of positron annihilation induced Auger-electron spectroscopy (PAES) are the missing secondary electron background in the energy region of Auger-transitions and its topmost layer sensitivity for elemental analysis. In order to enable the investigation of the electron polarization at surfaces low-energy spin-polarized positrons are used to probe the outermost electrons of the surface. Furthermore, in fundamental research the preparation of well defined surfaces tailored for the production of bound leptonic systems plays an outstanding role. In this report, it is envisaged to cover both, the fundamental aspects of positron surface interaction and the present status of surface studies using modern positron beam techniques.