Synthesis of hierarchical heterostructure of Si₃N₄/Si

Three-dimensional Si-based hierarchical heterostructures with the assistance of catalyst Fe have been synthesized by CVD process. It is found that the major stem wires are single-crystalline Si, and the side branches are single-crystalline Si₃N₄ nanowires. A plausible two-stage growth mechanism has been proposed for the formation of these uniquely stacked structures. Firstly, Si stems are formed via VS mechanism. Secondly, the catalyst Fe deposited onto the surfaces of the stem and then serves as the nucleate and growth sites for the formation of Si₃N₄ nanowires. The photoluminescence (PL) spectrum of the product shows a strong blue light emission centered at 413 nm with a shoulder at 440 nm under excitation at 360 nm.