Self-induced preparation of TiO2 nanowires by chemical vapor deposition

• The novel preparation of single crystalline TiO2 nanowires is reported by APCVD.
• The optimum conditions for high aspect ratio TiO2 nanowires growth are studied.
• The formation of TiO2 nanowires comes along with the consumption of TiSi2.
• The nanowires grow along with the [001] direction.

High-density single-crystalline TiO2 nanowires are successfully fabricated on a TiSi2 layer using a new self-induced catalyst-free method by APCVD. The results show that the high aspect ratio nanowires with diameters of 20–50 nm and lengths of about 3 μm are obtained on a TiSi2 layer at 720 °C. The length of TiO2 nanowires increases with the preparation time until Ti is exhausted. The nanowires shape changes with the concentration of O2 and temperature. When the temperature is above 720 °C or the flux of O2 is over 6 sccm, the density and length of nanowires decrease under the combined effect of the increasing lateral surface diffusion and longitudinal growth. The formation of TiO2 nanowires comes along with the consumption of TiSi2, TiO2 nanowires grow along the [001] direction of the tetragonal rutile TiO2 crystal from the bottom, with the tip being pushed upwards. The growth process is proposed which is consistent with our experiment results.