Fullerene and onion formation under electron irradiation of boron-doped graphite Original Research Article

The formation of single- and multi-shelled fullerene-type cages and onion-like nanoscale structures has been achieved in situ during electron irradiation of graphitic BxC1−x (x≤0.2) in a high resolution electron microscope. Once formed, the curled and closed structures were found to be quite stable to irradiation-induced damage. The B/C ratio was typically in the range of 0.02–0.10, as confirmed by electron energy loss spectroscopy using a 0.5 nm diameter electron probe. Unlike the quasi-spherical fullerene shape observed in pure carbon, the 2-D images of the boron-doped smaller fullerene-type cages resembled hexagons, and those of the larger curled objects revealed a polyhedral faceted shape suggestive of B-induced buckling of C-based curled structures. Similar to pure carbon onions, a dramatic shell spacing reduction for innermost layers compared to outermost layers was found in the B-doped multi-shelled curled and closed structures, indicating the possibility of B-doped diamond formation in the cores. The fullerene and onion morphology and some aspects of their formation and stability are discussed.