Simultaneous in situ and ex situ growth of ultra-long Si3N4 nanobelts with different optical properties

Abstract

In situ and ex situ growth of ultra-long Si₃N₄ nanobelts (NBs) was simultaneously achieved via an effective method with the raw materials of graphite, nanosilicon and nanosilica. In situ growth of ultra-long Si₃N₄ NBs on the surface of the powder mixture resulted in a cross-section of 30–50 nm in thickness and 100–250 nm in width, and a length that can grow up to several millimeters. The width and thickness of the NBs obtained on the inner walls of the crucible, namely ex situ growth of Si₃N₄ NBs, are in the range of 200–500 nm and 50–200 nm, respectively. A vapor–solid (VS) mechanism was proposed for the growth mode of the in situ growth of Si₃N₄ NBs, while VS and vapor–liquid–solid (VLS) mechanisms simultaneously existed in the growth of the Si₃N₄ NBs obtained on the inner walls of the crucible. This method provides an effective way of preparing Si₃N₄ NBs on an industrial scale. The room-temperature photoluminescence (PL) spectra show that the synthesized α-Si₃N₄ NBs both had two strong emissions peaks, but the PL spectrum of the ex situ NBs shows an obvious red-shift compared to that of the in situ NBs, making it a potential material for applications in special optoelectronic nanodevices.