Preparation of silica nanowires using porous silicon as Si source

► Layered porous silicon has been prepared by electrochemical etching process. ► Without the assistant metal catalyst, abundance silica nanowires have been grown in the cracks. ► The mechanism has been discussed and the induced stress may play an important role in the growth of silica nanowires. This very paper is focusing on the preparation of silica nano-wires via annealing porous silicon wafer at 1200°C in H2 atmosphere and without the assistant metal catalysts. X-ray diffraction, X-ray energy dispersion spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy and selected area diffraction technology have been employed for characterizing the structures, the morphology and the chemical components of the nano-wires prepared, respectively. It is found that the diameter and the length of the nano-wires were about 100nm and tens micron, respectively. Meanwhile, it is also necessary to be pointed out that silica NWs only formed in the cracks of porous wafers, where the stress induced both by the electro-chemical etching procedure for the porous silicon preparation and nanowires growth procedure is believed to be lower than that at the center of the island. Therefore, a stress-driven mechanism for the NWs growth model is proposed to explain these findings.