THE EXFOLIATION OF LIF IMPLANTED WITH ALKALI IONS AT LOW-TEMPERATURE

The implantation of alkali ions in LiF at liquid nitrogen temperature leads to the formation of a continuous metallic layer according to an insulator-metal transition. Due to the precipitation of the implanted ions, this metastable phase relaxes near room temperature giving rise to the formation of a granular layer. The depth distribution of the im planted ions determined by Rutherford Backscattering Spectrometry (RES ) shows the appearance of alkali ions at the crystal surface upon expo sure to the air. Such a profile is explained by the crystal exfoliatio n resulting from an explosive reaction of the implanted layer, which h as the properties of the bulk alkali metal Scanning electron microscop y (SEM) indicates that the thickness of the detached crystal platelets corresponds to the penetration depth of the incident ions, so that th e analysing beam detects in fact the implanted ions at the surface in the exfoliated regions.