STRUCTURAL INVESTIGATION OF XENON-ION-BEAM-IRRADIATED GLASSY-CARBON

Raman spectroscopy, cross-sectional transmission electron microscopy, and electron-energy-loss spectroscopy have been used to monitor the io n-beam-induced transformation in glassy carbon irradiated with 320-keV Xe ions to doses between 5 X 10(12) and 6 X 10(16) ions/cm2. It Was f ound that (i) the ion beam amorphizes the glassy carbon structure; (ii ) the amorphization is accompanied by a compaction of the glassy carbo n from an initial density of 1.55 to 2.2 +/- 0.2 g/cm3 ; and (iii) app roximately 15% of the graphite-like bonds in glassy carbon are convert ed to diamondlike bonds in the amorphization process. The transformati on of glassy carbon to an amorphous state occurs in two distinct stage s as a function of ion dose. For damage levels up to 0.2 displacements per atom (dpa) the effect of the ion beam is to decrease the average graphitic crystallite size. Above 0.2 dpa, disorder in bond length and bond angle away from ideal graphitic threefold coordination occurs le ading to complete amorphization at high doses. The amorphization, comp action, and presence of almost-equal-to 15% sp3 bonds in the implanted layer of glassy carbon results in a surface layer which is significan tly more resistant to abrasion than as-grown glassy carbon.