Growth of α-Si3N4 nanobelts via Ni-catalyzed thermal chemical vapour deposition and their violet-blue luminescent properties

alpha-Si3N4 nanobelts were grown on a graphitic carbon felt via an improved Ni-catalyzed chemical vapor deposition (CVD) process. The as-prepared nanobelts were up to several millimeters long and 300-1200 nm wide exhibiting a unimodal diameter distribution with peak range at 500-600 nm. Ni originally mixed with Si partially evaporated and then condensed on the carbon felt surface, forming catalytically active centers which absorbed gaseous Si and N and accelerated the growth of alpha-Si3N4 nanobelts. The formation process is considered to be co-dominated by a vapour-liquid-solid (VLS) base-growth mechanism and a vapour-solid (VS) tip-growth mechanism. The former was responsible for the initial nucleation and the proto-nanobelt formation and successive base-growth along the [101] direction of alpha-Si3N4, and the latter additionally contributed the growth at tips. The formation of alpha-Si3N4 nanobelts instead of nanowires is attributed to the anisotropic growth in the width and thickness directions, dictated by the liquid Ni catalyst droplets, in particular, in the initial proto-nanobelt formation stage. The room-temperature photoluminescence spectrum showed that the as-synthesized alpha-Si3N4 nanobelts had a strong emission with two maximum peaks at 416 nm (2.98 eV) and 436 nm (2.84 eV) located in the violet-blue spectral range, making it a potential material for applications in LED and optoelectronic nanodevices.