Photoluminescence in low defect density a-C:H and a-C:H:N

Films with paramagnetic defect density ∼1017 cm−3 of hydrogenated amorphous carbon (a-C:H) and nitrogenated and hydrogenated amorphous carbon (a-C:H:N) were grown on an earthed electrode of a radio-frequency (RF) driven plasma enhanced chemical vapour deposition system. The photoluminescence spectra had two bands at 562 nm (2.20±0.05 eV), and 612 nm (2.05±0.05 eV). The intensity of the 612 nm band increased relative to the intensity of the 562 nm band with increasing incorporation of nitrogen. Fourier transform infra-red spectroscopy results indicated there is also an increase in the CN triple bond fraction. The 612 nm band is attributed to π∗−π transitions within a CN triple bond cluster.