Non-catalytic vapor synthesis of millimeter-scale α-Si3N4 nanowires from oxidized silicon powders

• Si3N4 nanowires were first synthesized only through heating oxidized Si powders.
• The diameter of nanowires increased with change of oxygen content in Si powders.
• The nanowires grown from high oxygen-containing Si powders had high luminescence.
• Formation of α-Si3N4 nanowires followed an oxide-assisted growth mechanism.

Millimeter-scale single-crystalline α-Si3N4 nanowires were synthesized via heating oxidized silicon powders, without adding carbon and metal catalysts, at 1390 °C in N2 atmosphere based on an oxide-assisted growth process. The crystal structure, morphology and photoluminescence property of synthesized nanowires were investigated. With changing oxygen content of silicon powders from 3.28 wt% to 24.97 wt% by pre-oxidation, the average diameter of as-grown Si3N4 nanowires increased from 210 nm to 365 nm, however, the crystallized α-phase and [101] growth direction have not altered. The α-Si3N4 nanowires grown from the pre-oxided silicon powders have higher room temperature photoluminescence property than ones from the as-received silicon powders.