Raman spectra of diamondlike amorphous carbon films

Raman spectra of diamondlike amorphous carbon (a-C) films prepared under atmosphere with various hydrogen gas content have been measured as a function of excitation wavelength. The Raman spectral profiles vary with excitation wavelength depending on electronic absorption spectra associated with π-π* electronic transitions. Dependence of Raman spectra on excitation wavelength is interpreted in terms of π-π* resonant Raman scattering from aromatic rings with various sizes rather than polyene chains. The relative intensity of a 1400 cm−1 band against a 1530 cm−1 band is found to decrease with an increase of sp3 content in a-C films. It is shown that the relative intensity can be used as a parameter for sp3 content.