Raman scattering from ion-implanted graphite

Ion-implanted graphite is studied by Raman scattering. Highly oriented pyrolytic graphite is implanted with ⁷Li, ⁹Be, ¹¹B, ¹²C, ³¹P, and ⁷⁵As ions at 100 keV normally incident upon the c face. Ion fluences in the range 1 ×{} 10¹⁴ to 2.5 ×{} 10¹⁶ ions/cm² are used. The lattice damage upon implantation is monitored by observation of the disorder-induced Raman line at {~} 1355 cm^-1 in the first-order spectra and at {~} 2970 cm^-1 in the second-order spectra. The Raman results indicate that an abrupt transformation to an amorphous surface layer occurs at a critical fluence which varies with the mass of the implanted ion. Results for first- and second-order Raman spectra are also presented for the same ion-implanted samples upon isochronal vacuum annealing at various annealing temperatures, showing a partial restoration of the graphite ordering. The second-order Raman spectra are even more sensitive than the first-order spectra to the creation of lattice damage by ion implantation and to the subsequent partial restoration of lattice order by annealing.