Surface hardness enhancement in ion-implanted amorphous carbon

The feasibility of producing carbon nitride has been studied by ion implantation into amorphous carbon. Thin films were formed with 100 keV N+ or 80 keV C+ ions al various target temperatures and ion doses. The apparent surface hardness measured by nanoindentation with load-displacement data shows an optimum value of 22.3 +/- 0.4 GPa with the ion dose of 2 X 10(17) N+/cm(2) implanted at -100 degrees C, while the hardness of the unimplanted amorphous carbon is 6.0 +/- 0.2 GPa. Self-implantation by carbon also produces similar hardness enhancement with a narrow temperature window. The maximum enhanced surface hardness is well correlated with the asymmetric diffuse peak at around 1500 cm(-1) in Raman spectroscopy. (C) 1996 American Institute of Physics.