Creation and clustering of Frenkel defects at high density of electronic excitations in wide-gap materials

Abstract

A complex nature of the dependence of the intensity of intrinsic or impurity emission on the excitation density by single electron pulses is determined by the existence or absence of self-trapped holes and/or excitons in ZnS, BaF2, MgO, BeO and Al2O3. A powerful electron (300keV) or ion (Au, U, ∼2GeV) irradiation of pure and doped LiF, MgO and Al2O3 crystals induces the optical absorption, certain high-temperature annealing stages of which appear only under high LET conditions. Swift-ion-irradiation causes drastic changes in the spectrum of fundamental reflection of LiF, especially in the region of the exciton resonance. The irradiation providing high density of electronic excitations (LET>20keV/nm) leads not only to the creation of stable Frenkel defects but also to the excitation of a whole group of crystal ions, thus, causing the creation of bivacancies, lithium and fluorine interstitials as well as their associations/clusters.