Scanning Microscopy


Positron-electron annihilation in condensed matter provides a way to investigate the electronic structure. the annihilation characteristics depending on the electronic structure of the environment sampled by positrons. The relatively recent production of intense low energy positron beams has made the study of surfaces with positrons possible. The near surface region can be studied by implantation of slow monoenergetic positrons via positron electron annihilation and, in addition. via positron diffusion length measurements. This is a powerful method to study vacancy type defects in the near surface region because positively charged positrons are normally very efficiently trapped by vacancy defects. The experiments reviewed in this tutorial paper show that, by using slow positron beams, one can study (i) vacancy profile defects in the near surface region, vacancy defects at interfaces, (ii) electron momentum density, electron density of states and magnetism at surface, and (iii) surface structure.

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