Resonant Raman scattering from N-doped and Si-doped diamondlike amorphous carbon films

Abstract

We measured the Raman spectra of Si- and N-doped diamondlike amorphous carbon $(a\ensuremath{-}\mathrm{C}:\mathrm{H})$ films as a function of the excitation wavelength and found that the Raman spectral profiles of these samples varied with the excitation wavelength, depending on the optical band gap. The variation of Raman spectra with the excitation wavelength observed for Si- and N-doped $a\ensuremath{-}\mathrm{C}:\mathrm{H}$ films was interpreted in terms of $\ensuremath{\pi}\ensuremath{-}{\ensuremath{\pi}}^{*}$ resonant Raman scattering from ${\mathrm{sp}}^{2}$ carbon clusters having various sizes. Furthermore, it was found that the incorporation of Si into carbon network structures promoted the formation of ${\mathrm{sp}}^{3}$ carbon clusters whereas the incorporation of N atoms into carbon network structures promoted the formation of ${\mathrm{sp}}^{2}$ carbon clusters. A comparison was made between Stokes and anti-Stokes Raman spectra of glassy carbon and Si-doped $a\ensuremath{-}\mathrm{C}:\mathrm{H}$ film, and the peak-frequency shift of the main peak with the excitation energy for $a\ensuremath{-}\mathrm{C}:\mathrm{H}$ films. This comparison indicated that the double resonance Raman process contributed very little to the resonance Raman scattering from $a\ensuremath{-}\mathrm{C}:\mathrm{H}$ films consisting of a mixture of ${\mathrm{sp}}^{3}$ and ${\mathrm{sp}}^{2}$ carbon clusters.