A review of colour center and nanostructure creation in LiF under heavy ion irradiation

Abstract

A study of radiation damage in LiF crystals under irradiation with MeV–GeV energy ions, from 12C to 238U, at temperatures varying from 8 to 300 K, depending on the ion energy, energy loss and irradiation temperature, is presented. For light ions (12C, 14N) at low fluences, it is mainly color centers that are created. Increasing the fluence leads to the overlapping of tracks and the creation of more complex color centers, defect aggregates and dislocations. For ions with an energy loss above a threshold value (dE/dx = 10 keV nm−1) the tracks exhibit a central core damage region with a radius of 1–2 nm, surrounded by an extended halo which mainly contains single color centers. In this case, ion-induced nanostructuring is observed. Novel effects of radiation damage creation under ion irradiation at 8 K are observed. The role of energy loss and irradiation temperature in damage creation is discussed.

Formation of dislocations and hardening of LiF under high-dose irradiation with 5–21 MeV 12C ions

“…At comparable fluences, light ions create less pronounced changes in the structure and properties [5][6][7]. A difference in the damage produced by heavy and light ions manifests already in the structure of individual tracks.…”

“…In the studies of swift ion-induced damage, LiF crystals play an important role due to their high-radiation sensitivity and the significance for various applications (colorcenter lasers, dosimeters, etc. ) [3][4][5]. In contrast to many insulators, LiF does not amorphize even under a high dose of irradiation.…”

“…This property is characteristic for materials with a strong ionic bonding. Previous studies have shown remarkable SHI-induced changes of structure, optical, mechanical, and other properties in LiF [2][3][4][5][6][7][8][9]. At high-fluence irradiations, an accumulation of extended defects (dislocation loops and other aggregates of defects), nanostructuring, and substantial hardening were observed.…”

Accumulation of radiation defects and modification of micromechanical properties under MgO crystal irradiation with swift 132Xe ions

“…3, xenon ions create very low concentration of F2 centers (see optical density values at right ordinate) and, moreover, there is even decrease of the number of F2 centers (as well as F2/F ratio) at Φ ≥ 10 13 Xe/cm 2 . This result contradicts the case of LiF crystals, where comparable amount of F and F2 centers and nearly constant ratio of F2/F was detected under swift-ionirradiation up to saturation level different for N and Kr ions, when creation of more complex aggregates Fn became dominant [41,42]. Such difference in accumulation processes of F-type centers in MgO (EFD > Eg) and LiF (EFD < Eg) can be explained by different contribution of ionization and displacement mechanisms of radiation damage.…”

“…On the other hand, the creation efficiency of the simplest aggregateF2 centers is very low and demonstrates fluence dependence of complicated shape. The latter fact testifies to rather low (but still measurable, see below) in-volvement of ionization mechanisms (EE-related), responsible for effi-cient creation of aggregate centers at higher fluence in wide-gap ma-terials with EFD < Eg (in particular LiF [41,42]), in damage of MgO (EFD > Eg) under swift ion irradiation.…”