Facile conversion of silicon nitride nanobelts into sandwich-like nanosaws II: growth mechanism and optical properties

In a previous paper (G.F. Guo et al., Appl. Phys. A, 2009), the microstructures of sandwich-like nanosaws have been revealed clearly. Here, the growth mechanism and optical properties of Si3N4 sandwich-like nanosaws were further investigated. It is assumed that the growth atmosphere with a large amount of *N (active nitrogen) from the decomposition of NH3 would be the key factor for the formation of sandwich-like nanosaws during the catalyst-assisted pyrolysis of the polymeric precursors. From the characterizations of TEM together with the systematic composition analysis, we found that a large excess of nitrogen element occurred in the central “soldering” region as well as high density defects, which induced the asymmetric growth of nanoteeth on the original nanobelt sidewall, forming into a sandwich-like nanosaw morphology. The unique optical properties of sandwich-like nanosaws could be attributed from the presence of a large amount of nitrogen dangling bond defects in the central “soldering” region, and a new optical band-gap model was proposed for the interpretation of the photoluminescence spectra.