INFLUENCE OF THE IMPLANTATION PARAMETERS ON THE MICROSTRUCTURE OF CARBON ONIONS PRODUCED BY CARBON ION-IMPLANTATION

We study the influence of implantation parameters (temperature, implan ted dose, and current density) on the microstructure of carbon onions produced by carbon ion implantation into silver substrates held at ele vated temperature. Carbon onions are synthesized only for temperatures higher than 400 degrees C. An increase of the average diameter of the onions as well as a structure presenting less defects are observed wh en the temperature increases from 500 to 800 degrees C. For implantati on doses varying from 5 x 10(16) cm(-2) to 5 x 10(17) cm(-2), we obser ve an increase of the average diameter, spherical onions with a very s harp distribution in size being obtained for doses less than or equal to 10(17) cm(-2). We also vary the current density of the carbon ion b eam from 2 to 45 mu A cm(-2), but this parameter does not induce any v isible microstructural evolution of the onions. From the results prese nted here, one can now carry out studies related to the evolution of t he physical properties of well defined size carbon onions having a con trolled amount of defects. (C) 1998 American Institute of Physics. [S0 003-6951(98)04844-X].