Formation Mechanism of Amorphous Silicon Nanoparticles Synthesized by Induction Thermal Plasma

Abstract

This study focus on the synthesis of amorphous silicon nanoparticles and understanding the formation mechanism. Counter-flow quenching gases with different flow rates were injected from downstream of the torch to understand the effect of quenching gas on the formation of silicon nanoparticles. Transmission electron microscopy show that nanoparticles with spherical shape and agglomerates consist of smaller particles were synthesized. X-ray diffraction analysis is used to calculate the amorphization degree, which is defined as fraction of amorphous silicon in the silicon nanoparticles including both crystal and amorphous. The obtained results show that higher quenching gas flow rate leads to smaller diameter with higher amorphization degree. Electron diffraction patterns reveal that nanoparticles with diameter less than 10 nm are amorphous and agglomerated together, while for the nanoparticles with diameter larger than 10 nm are crystal. The formation mechanism of amorphous silicon nanoparticles is explained by estimated nucleation temperature and experimental results. Consequently, silicon nucleates at about 2400 K and then silicon vapor condenses on the nucleus. Finally, smaller nanoparticles will keep amorphous phase, while nanoparticles with a larger diameter grow to form crystalline.

Effect of Methane Injection Methods on the Preparation of Silicon Nanoparticles with Carbon Coating in Induction Thermal Plasma

“…We reported a one-step formation method of carbon coated SiNPs with induction thermal plasma in a recent paper (Zhang et al, 2020). Induction thermal plasma is attractive to synthesize nanoparticles with high purity due to its advantages, such as high temperature (over 10 4 K), long residence time for precursors (several to hundreds of milliseconds), outstanding quenching e ect (10 3 -10 6 K/s), and electrodeless characterization (Tanaka et al, 2016;Zhang et al, 2021c). Previous studies already demonstrated the hydrocarbon decomposition processing and the subsequent surface reactions, which are in uenced by the ambient temperature of reaction chamber, can determine the formation of carbon coating as well as the coating properties (Zhang et al, 2021b).…”