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

Abstract

α-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 α-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 α-Si₃N₄, and the latter additionally contributed the growth at tips. The formation of α-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 α-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.