Thermal evaporation growth and the luminescence property of TiO2 nanowires

Single crystalline TiO2 nanowires have been successfully grown on alumina substrates using a high-frequency (350 KHz) dielectric heater at 1050 °C by a two-step of thermal evaporation method without using any catalyst. The first step is to form the high surface energy TiO2 seeds on the low surface energy alumina substrates. The second step is to grow the single crystalline TiO2 nanowires on the alumina substrates by the vapor-solid (VS) mechanism. The field emission electron microscopy (FESEM) image showed a uniform diameter of 60-90 nm and length of hundreds of nm to 2 μm for the TiO2 nanowires. The high-resolution transmission electron microscopy (HRTEM) image showed that the TiO2 nanowires are of single crystalline rutile structure. The luminescence properties were investigated by cathodoluminescence (CL) in FESEM. The result is surprising in that the TiO2 nanowires are of rutile phase, but the luminescence properties similar to the bulk TiO2 of anatase phase.