Raman scattering fromsp2carbon clusters

Raman spectra of B ion-implanted glassy carbon (GC) and hydrogenated amorphous carbon (a-C:H) films have been measured as a function of polarization direction of the scattered light and excitation wavelength. Raman bands of GC implanted heavily with a fluence of more than 5×${10}^{15}$ B ions/${\mathrm{cm}}^2$ and a-C:H films show a frequency-independent depolarization ratio, suggesting the existence of ${\mathit{sp}}^2$ carbon clusters in these samples. It was found that Raman spectra of GC implanted heavily with a fluence of more than 5×${10}^{15}$ B ions/${\mathrm{cm}}^2$ varied with the excitation wavelength. From a comparative study of the heavily implanted GC and a-C:H films, the variation of the Raman spectra with the excitation wavelength observed for the heavily implanted GC is interpreted in terms of π-${\mathrm{\pi }}^{\mathrm{*}}$ resonant Raman scattering from ${\mathit{sp}}^2$ carbon clusters having various sizes.