Morphology instability of silicon nitride nanowires

We report that cylinder-shaped Si ₃N ₄ nanowires are not stable and can gradually transform into nanobelts via surface diffusion during high-temperature annealing. We demonstrate that such instability is driven by the requirements for reducing overall surface energy. The resultant nanobelts have the same width-to-thickness ratio, suggesting a stable morphology. A model in terms of surface energy is proposed to explain the formation of such stable morphology, which agrees well with experimental results. Our result suggests that instability could be a limiting factor for high-temperature applications of 1D nanostructures.