Solid-state Si-29 NMR analysis of amorphous silicon nitride powder

Solid-state Si-29 NMR techniques were used to characterize laser-synthesized silicon nitride powder prepared from the reaction of silane with ammonia, When the powder is exposed to water vapor, a hydrated layer rapidly forms at the surface. A comparison of Si-29 cross polarization (CP) and Bloch decay (BD)-MAS-NMR spectra revealed differences between surface and bulk compositions, CP-NMR identified Si-NHx (x = 1, 2) species with a chemical shift of -45 ppm in the as-synthesized (unexposed) powder. In BD-NMR spectra, the nitride resonance is observed at -48 ppm. For the hydrated powder, CP-NMR identified additional =Si-OH (Q(3)), =Si-(OH)(2) (Q(2)), and SiO2 (Q(4)) species present at the surface, The CP-NMR spectra were corrected for T-1 rho H relaxation effects and deconvoluted into individual components in order to extract quantitative measurements of the various species present.