Growth Kinetics of Needle-like Silicon Wires Formed via the Zinc Reduction Reaction of Silicon Tetrachloride

We studied the growth kinetics of needle-like silicon wires formed in the reduction reaction of silicon tetrachloride (SiCl4) with zinc vapor. Real-time monitoring of the silicon wire growth was performed using a quartz tube reactor with a charge-coupled device (CCD) camera. The formation of silicon wires was observed when SiCl4 was mixed with zinc vapor; the wires grew at a constant rate, which reached 20 mm min–1. We did not prepare catalytic metal particles in the reactor; however, since zinc metal can form a liquid alloy with silicon at reaction temperatures of ca. 900–950 °C, we proposed that a vapor–liquid–solid (VLS) mechanism was responsible for the formation of the silicon wires. We consider that the zinc acted both as a reducing agent for SiCl4 and as a metal catalyst for the wire formation. On the basis of the VLS mechanism, a simple kinetic model for wire growth was proposed. Our model described the experimental data well, and the rate-limiting step for the wire growth is the gas-phase reduction of SiCl4. The activation energy for the wire growth was 2.8 × 102 kJ mol–1.