Atomic-scale assessment of the crystallization onset in silicon carbonitride

Within the present study, atomic-scale electron microscopy investigation on the crystallization behavior of polysilylcarbodiimide-derived SiCN was performed. The as-prepared SiCN sample was found to be homogeneous and consisted of amorphous silicon nitride nano-domains dispersed within an amorphous, highly entangled graphene-like carbon matrix. Annealing of the sample at 1400°C induced a slight increase of the ordering of the carbon phase. Additionally, the crystallization onset of the silicon nitride has been observed for the first time. In the sample annealed at 1400°C small nano-clusters with average sizes of 0.8, 1.5 and 2.1nm (consisting of 30, 180 and 570 atoms, respectively; corresponding to Si₁₂N₁₈, Si₇₂N₁₀₈ and Si₂₂₈N₃₄₂) were imaged and assigned to α-silicon nitride. The crystallization of the amorphous silicon nitride phase into α-Si₃N₄ is thought to occur via diffusion of Si and N, which rely on the presence of large number of dangling bonds in the amorphous SiCN sample.