The role of self-trapped excitons in radiation-damage processes in insulators

Abstract

We review current studies on defect formation induced by valence-electron excitation in insulators. Emphasis is placed on the role of self-trapped excitons in damage processes. First we classify the processes into a few cases, based on categorization of materials in terms of energy localization and on the density of excitation. Then defect formation in alkali halides, which is a typical example of single-excitation process, is discussed to clarify the origin of the dependence of the efficiency on materials. Finally, the effects of the density of excitation on defect formation are discussed, presenting some pieces of evidence that excitation of the self-trapped exciton and the interaction of free excitons and self-trapped excitons produce Frenkel pairs in materials which are highly resistive to single-excitation processes.