Fullerene onion formation by carbon-ion implantation into copper

We have performed high-dose carbon-ion implantations into copper substrates at high temperature with the objective of producing single crystalline diamond thin films. An important density of giant carbon onions has been identified in a turbostratic graphite layer formed on the copper surface. We have characterized these giant fullerenes (up to 1 mu m in diameter) by transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and electron energy loss spectroscopy (EELS), and we propose two possible mechanisms of formation of the carbon onions during the implantation process.