Surface superstructure of Arc(+)-bombarded highly oriented pyrolytic graphite during recrystallization

The recrystallization process of highly oriented pyrolytic graphite (HOPG) surface bombarded by argon ions with an ion energy of 2.0-2.5 keV at doses of 2-5x10(16) ions/cm(2) was examined by scanning tunneling microscopy. The hillocks formed by the ion bombardment of HOPG coalesced to form larger gr ains with increasing annealing temperature. Three types of ringlike superst ructures of (root 3 x root 3)R30 degrees of graphite were found on the curv ed surface of the grains after annealing in the temperature range of 1823-2 673 K. The specimen surface became flat above 2773 K, where the ringlike su perstructure disappeared and the triangular structure of graphite appeared in its place. The effect of the curved surface of the grains on the formati on of the ringlike superstructure during graphitization is discussed. (C) 1 999 American Vacuum Society. [S0734-211X(99)04406-6].