Investigating the possible origin of Raman bands in defective sp2/sp3 carbons below 900 cm−1: Phonon density of states or double resonance mechanism at play?

Multiwavelength Raman spectroscopy (325, 514, 633 nm) was used to analyze three different kinds of samples containing sp2 and sp3 carbons: chemical vapor deposited diamond films of varying microstructure, a plasma-enhanced chemical vapor deposited hydrogenated amorphous carbon film heated at 500 °C and highly oriented pyrolytic graphite exposed...