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 hydrog en, carbon and nickel ion implantations on graphite samples. In the case of H implantation, the induced disorder decreased after annealing at 650 degr eesC for 7.7 GPa. For C implantation, the defect annealing started at 500 d egreesC for 7.7 GPa, while in the case of Ni implantation, it started at 85 0 degreesC for the same pressure. For the three cases studied, there was pr actically no annealing effect for temperature treatments in vacuum up to 11 00 degreesC, The results indicated that high pressure plays an important ro le in the defect annealing, accelerating the graphitization process, probab ly due to the large volume of the defective ion implanted phase. Despite th e annealing at high pressure being conducted deep inside the thermodynamic region of stability of diamond? the graphite phase was recovered, indicatin g that the nucleation barrier for diamond is indeed very high as compared t o graphite. (C) 2001 Elsevier Science B.V. All rights reserved.