Connection between Si–N and Si–H vibrational properties in amorphous SiNx: H films

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Abstract
Amorphous SINx: H films have been prepared by r.f. glow discharge of SiH4–N 2–H2 mixtures at 300°C, and the dependence on x of the Si–N and Si–H absorption bands investigated by infrared absorption spectroscopy. The stretching absorption profiles due to Si–N bonds are reproduced by a superposition of three components with Gaussian shapes at around 750,840 and 960 cm−1, and a N-atom related Si–H absorption is observed at around 2100cm−1. The weak 750cm−1 band, observed at the lower levels of x, is assigned to isolated Si–N bonds. Clear changes in the dependence of these absorption bands on x are observed at around x = 0·5. Up to x = 0·5, the 840 and 2100cm−1 bands increase with x keeping a fixed peak wavenumber, and also giving agreement between the N and H contents estimated from the intensity of each band. This indicates selectively increased formation of N–Si–H bonds, responsible for both bands at 840 and 2100 cm−1. Above x = 0·5, the 960 cm−1 band occurs, and the peak wavenumbers of the 960 and 2100cm−1 bands increase with x. The intensities of the 840 and 960cm−1 bands increase with x, while that of the 2100cm−1 band decreases. This is interpreted as indicating formation of Si–N–Si·Nn and N–Si·Si·Nn bonds (840 cm−1), and of Nn–Si(–H) bonds (960 and 2100cm−1), brought about by further replacement by N atoms of the H and Si nearest neighbours to the Si site in N–Si–H bonds.