Growth of TiO2 nanorods by two-step thermal evaporation

The unique morphology of TiO2 nanorods grown in a two-step thermal evaporation process under a controlled atmosphere was observed. The first step attempts to form TiO2 seeds with a higher surface energy on the alumina substrate with lower surface energy; the second step is the growth of the TiO2 seeds gradually to form nanorods. Field emission scanning electron microscopy and Raman spectrometry were used to elucidate the morphology and the characteristic spectra, respectively. The nanorods were composed of nanobricks. The nanorods were 70–150nm in diameter and up to 2μm long, respectively. High-resolution transmission electron microscopy demonstrated that an individual nanorod exhibits a twin structure with a body-centered tetragonal rutile phase, and grows in the [110] direction. Its optical response shows a broad blue emission peak at ∼418nm as cathodoluminescence analysis.