Two-dimensional metal inclusions in a dielectric crystal

Highly aggregated color centers in crystals of a wide-band-gap calcium fluoride insulator heated in a reducing atmosphere of vapors of calcium metal cation (“additive coloration” of crystals) have been studied using spectroscopy and atomic-force microscopy methods. These centers are large aggregates of anion vacancies and electrons, which transform into metal structures. The evolution of these structures with increasing number of such components has been traced from individual particles with two-dimensional structure to large film fragments. It has been shown that fragments are concentrated in isolated planes {111}, which are cleavage planes of the crystal with high contents of highly aggregated centers.