Structural characterization of ion implanted pyrolytic graphite

Raman spectroscopic and optical microscopic studies have been made to analyze the structure of highly oriented pyrolytic graphite (HOPG) modified by 150 keV N+ implantation. Raman spectra showed that the graphite structure was disordered and polyacetylene-like carbon (PALC) was generated in the ion implanted surface layer. Volume fractions of PALC estimated by multicomponent Raman spectral analysis, increased with increase of fluence below 1 x 10(16) ions/cm(2) of N+ implantation. The volume fraction of the PALC increased with decrease of the target temperature. By optical microscopic observation, clear sub-millimeter cracks were found on the specimens implanted with above 1 x 10(15) ions/cm(2) at the target temperature of about 25 degrees C. The crack area enlerged with increase of N+ fluence. For the specimens with fluence of 1 x 10(16) ions/cm(2), the clear cracks appeared on the specimens implanted below 200 degrees C. The crack area enlerged with decrease of the target temperature. It was obvious that the enlergement of the crack area correlated positively to the increasing of the volume fraction of PALC. (c) 2007 Elsevier B.V. All rights reserved.