| Popis: |
Ion-implanted graphite is studied by Raman scattering. Highly oriented pyrolytic graphite is implanted with $^{7}\mathrm{Li}$, $^{9}\mathrm{Be}$, $^{11}\mathrm{B}$, $^{12}\mathrm{C}$, $^{31}\mathrm{P}$, and $^{75}\mathrm{As}$ ions at 100 keV normally incident upon the $c$ face. Ion fluences in the range 1 \ifmmode\times\else\texttimes\fi{} ${10}^{14}$ to 2.5 \ifmmode\times\else\texttimes\fi{} ${10}^{16}$ ions/${\mathrm{cm}}^{2}$ are used. The lattice damage upon implantation is monitored by observation of the disorder-induced Raman line at \ensuremath{\sim} 1355 ${\mathrm{cm}}^{\ensuremath{-}1}$ in the first-order spectra and at \ensuremath{\sim} 2970 ${\mathrm{cm}}^{\ensuremath{-}1}$ 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. |
