Direct quantitative detection of the sp(3) bonding in diamond-like carbon films using ultraviolet and visible Raman spectroscopy

The bonding in a series of unhydrogenated amorphous carbon films has been a nalyzed quantitatively using Raman spectroscopy excited by laser light in b oth the visible and ultraviolet regions of the spectrum. The asymmetry of t he peak near 1550 cm(-1) in the visible Raman spectra is correlated with th e percentage of sp(3) bonding in the films. The ultraviolet Raman spectra e xhibit two broad Raman peaks at 1650 and 1100 cm(-1), due to sp(2) and sp(3 ) vibrational modes, respectively. The former is a resonance feature associ ated with a large proportion of paired sp(2) sites, while the latter is a w eighted phonon density-of-states for the distorted random network of sp(3) sites. The position and relative intensity of the two peaks are shown to be strongly correlated with the percentage of sp(3) sites in the films, provi ding a reliable measure of sp(3) bonding which is both semiquantitative and nondestructive. (C) 2000 American Institute of Physics. [S0021-8979(00)048 10-6].