Positron Annihilation Spectroscopy

Abstract

Positron annihilation spectroscopy (PAS) has in recent years become an increasingly valuable tool for the study of the electronic and defect struc­ tures of materials. Owing to the ability of the positron to annihilate from a variety of specific states in solids, ranging from an extended state in a defect-free lattice to highly localized states in lattice defects, PAS can yield unique information regarding various properties of materials. The unique aspects of PAS arise from the fact that the positron-electron pair annihilation process, which proceeds by the emission of y rays, can yield detailed information regarding both the electron density and the electron momenta in the region from which the positron annihilates. The physical basis of positron annihilation in condensed matter and the applications of PAS to the study of solids have been extensively reviewed elsewhere (1-4). In addition, several reviews of various aspects of the application of PAS to the study of electronic structure (5-10) and defects in materials (1 1-20) have been published. The present paper is intended as a brief introduction to positron annihilation, and its recent literature, and to the applications of PAS in the area of materials science, with particular emphasis on metals and alloys. As such, this review will use selected examples from the literature to discuss some recent advances in this relatively new research area as well as some of the future potential of PAS for the study of materials. The present work is based, in part, on a previous short review (20) by this author.