Abstract
Solid state phase transformations of diamond- and graphite-like allotropies in the C-B-N system into single- or multi-layer Russian doll type fullerene cages were observed in-situ in a JEM-3000F field emission 300 kV high resolution transmission electron microscope during intense electron irradiation. Electron flux densities were up to 10 times higher than those under normal imaging conditions. Irradiation experiments were run on synthetic diamond single crystals, graphitic B-doped carbon, hexagonal, rhombohedral and turbostratic BN. In contrast to conventional fullerene synthesis from the gas phase, solid state phase transformation proceeds by curling and winding of the graphene-like layers followed by atomic rearrangement into entirely closed shells due to the drastic increase in thermal and irradiation-induced diffusion and elimination of dangling bonds. Ab-initio and tight binding scheme total energy calculations of fullerene stability were carried out to construct 3-D structural models.