Kinetic study of the oxide-assisted catalyst-free synthesis of silicon nitride nanowires

TL;DR

This study investigates the oxide-assisted, catalyst-free synthesis of silicon nitride nanowires from silicon nanoparticles, revealing that intrinsic nitridation kinetics are temperature-independent and influenced by particle stacking effects.

Contribution

It provides new insights into the intrinsic kinetics of silicon nitridation without catalysts and highlights the impact of particle amount on reaction rates.

Findings

Nitridation rate depends on silicon particle amount.

Intrinsic kinetics are temperature-independent.

Particle stacking inhibits gas exchange and affects reaction.

Abstract

The synthesis of Si3N4 nanowires from the reaction of silicon nanoparticles with N2 in the 1200-1440 C temperature range is reported. The nitridation conditions are such that the reaction with nitrogen is favoured by the presence of silicon oxide in the particles and by the active oxidation of silicon without a catalyst. It is shown that the Si to Si3N4 conversion rate depends on the amount of silicon particles used in the experiments and that, in general, the reaction slows down for greater amounts. This trend is explained by particle stacking, which restricts the exchange of gases between the furnace atmosphere and the atmosphere around the inner particles. In a first stage, local oxygen partial pressure increases around the inner particles and inhibits nitridation locally. If the amount of reactant Si nanoparticles is small enough, this extrinsic effect is avoided and the intrinsic nitridation kinetics can be measured. Experiments show that intrinsic kinetics does not depend on temperature.