The exfoliation of LiF implanted with alkali ions at low temperature

Abstract

Abstract 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 implanted ions determined by Rutherford Backscattering Spectrometry (RBS) shows the appearance of alkali ions at the crystal surface upon exposure to the air. Such a profile is explained by the crystal exfoliation resulting from an explosive reaction of the implanted layer, which has the properties of the bulk alkali metal. Scanning electron microscopy (SEM) indicates that the thickness of the detached crystal platelets corresponds to the penetration depth of the incident ions, so that the analysing beam detects in fact the implanted ions at the surface in the exfoliated regions.