EELS STUDY OF THE IRRADIATION-INDUCED COMPRESSION OF CARBON ONIONS AND THEIR TRANSFORMATION TO DIAMOND

The irradiation-induced self-compression of carbon onions and their tr ansformation to diamond crystals are studied in situ by electron energ y loss spectroscopy at high specimen temperature in a high-voltage ele ctron microscope. Plasmon peaks in the low-loss region and the carbon K edge with the near-edge fine structure exhibit characteristic change s during irradiation. The spectra show the increasing electron density and the gradual change from sp(2) to sp(3) character of bonding durin g the self-compression of carbon onions. The spectra of the diamond co res correspond closely to those of cubic high-pressure diamonds. (C) 1 998 Elsevier Science Ltd. All rights reserved.