Raman ‘‘fingerprinting’’ of amorphous carbon films

We compare the Raman spectra and other macroscopic properties of nearly one hundred amorphous carbon films deposited at five research laboratories by a total of five different methods in search of correlations useful for both process control and basic understanding of the structure of these materials. For the full range of carbon-hydrogen alloys, including so-called ‘‘amorphous diamond,’’ hydrogenated ‘‘diamondlike’’ carbon, and plasma-polymers, a simple parametrization of the Raman spectrum in the usual 1000 cm−1 to 2000 cm−1 range can be used as a reliable predictor of hydrogenation and other properties (e.g., optical gap, hardness). Raman features in the 200 cm−1 to 1000 cm−1 range, a spectral region not usually reported for carbon films, may also be used as an indicator of hydrogenation. These growth method independent correlations greatly enhance the utility of Raman spectroscopy as a non-destructive characterization and process control tool.