A phenomenological approach for the Id/Ig ratio and sp3 fraction of magnetron sputtered a-C films

Amorphous carbon coatings (a-C and a-C:H) less than 100 nm thick were deposited on KBr, and silicon wafer substrates via magnetron sputtering of a graphite target in argon, argon/hydrogen and argon/nitrogen atmospheres. Electron energy loss spectroscopy (EELS) analysis was used to quantify the sp2/sp3 bonding in the films. Free-standing films of amorphous carbon were produced by sputtering onto compressed KBr pellets and then floating off in distilled water for EELS study. Raman spectroscopy was used to measure the peak intensity ratio of the D-band to that of the G-band (Id/Ig). This showed that the sp3 fraction is inversely proportional to the band ratio Id/Ig. At the same time, the G-band peak position Pg decreases while the sp3 fraction increases.