High pressure annealing of defects induced by ion implantation on graphite

The aim of this work was to investigate, by Raman spectroscopy, the effect of high pressure on the annealing of the surface disorder induced by hydrogen, carbon and nickel ion implantations on graphite samples. In the case of H implantation, the induced disorder decreased after annealing at 650 degreesC for 7.7 GPa. For C implantation, the defect annealing started at 500 degreesC for 7.7 GPa, while in the case of Ni implantation, it started at 850 degreesC for the same pressure. For the three cases studied, there was practically no annealing effect for temperature treatments in vacuum up to 1100 degreesC, The results indicated that high pressure plays an important role in the defect annealing, accelerating the graphitization process, probably due to the large volume of the defective ion implanted phase. Despite the annealing at high pressure being conducted deep inside the thermodynamic region of stability of diamond? the graphite phase was recovered, indicating that the nucleation barrier for diamond is indeed very high as compared to graphite. (C) 2001 Elsevier Science B.V. All rights reserved.