Raman spectroscopy on amorphous carbon films

The origin and interpretation of the Raman features of amorphous (hydrogenated) carbonfilmsdeposited at room temperature in the region of 1000–1700 cm−1 is discussed in this paper. Possible interpretations of the linewidths, positions of the ‘‘G’’ graphite peak and ‘‘D’’ disordered peak, and their intensity ratios are examined using results obtained from magnetron sputtered and magnetic field enhanced plasmadepositedfilms. It is shown that even small ‘‘clusters’’ of condensed benzene rings (cluster size below 20 A) in carbonfilms can explain the observed Raman scattering. Besides the care that should be taken in the correct interpretation of Raman results, the utility of Raman scattering in obtaining an estimate of cluster sizes in amorphous (hydrogenated) carbonfilms is discussed. Carbonfilms prepared by magnetron sputtering show two additional Raman features at 1180 and 1490 cm−1 in addition to the G and D peaks. It is shown that a correlation exists between the 1180 cm−1 peak and the sp 3 content in the films.