Formation mechanism of amorphous silicon nanoparticles with additional counter-flow quenching gas by induction thermal plasma

The fabrication process of amorphous silicon nanoparticles by induction thermal plasma was studied by experiments and numerical simulations. Additional quenching gas was introduced as counter-flow to the plasma tail flame to enhance quenching effect. The flow rate of quenching gas ranged from 0 to 70 L/min. Amorphous silicon nanoparticles were confirmed by electronic diffraction analysis with random shapes and serious agglomerate, while the crystal particles had a totally different morphology of spherical and freestanding. The quenching rate was estimated on the basis of numerical results and increased from 3.2 × 10⁴ to 8.9 × 10⁵ K/s with quenching gas flow rate. The amount of amorphous silicon increased as quenching gas injection and should be attributed to the improved preparation of small nanoparticles (<5 nm). The above results suggested the formation of amorphous silicon in thermal plasma is controllable.