ABSTRACTWe have identified longitudinal and transverse optical modes of Si-N bond in vibrational absorption spectrum of hydrogenated amorphous silicon nitride thin films. The locations of longitudinal optical resonances coincide with transverse mode of Si-O and closely neighbor bending modes of N-H, Si-H2 bond. Furthermore, the conventionally assigned asymmetric and symmetric stretching modes of Si-N bond are merely transverse modes of Si-N bond. Features of pure longitudinal vibrational modes can be revealed by subtracting appropriately scaled transverse mode components from the vibrational absorption spectrum. Analysis of the longitudinal spectrum indicates that, in addition to their association with Si-N bond, the density of the peak located at about 1215 cm−1 is also well correlated to hydrogen and nitride content in the film, while the density of the peak located at about 880 cm−1 is closed related to silicon density in the film. Peak located at about 1040 cm−1 is the longitudinal mode associated with Si-N bond.
Observation of “fast” and “slow” decay processes in oxygen-doped hydrogenated amorphous silicon nitride thin films
