Growth of rutile TiO₂ nanorods on anatase TiO₂ thin films on Si-based substrates

Synthesis of titania (TiO₂) nanorods on various substrates has recently attracted attention for energy and environmental applications. Herein, we report growth of nanostructured TiO₂ on Si(111) and glass borosilicate substrates by a two-step method. A thin film of anatase TiO ₂ was first laid down by spin coating and annealing, followed by the growth of rutile TiO₂ nanorods with a hydrothermal method. To understand the role of the polycrystalline anatase TiO₂ seed layer, we selected a relatively high temperature for the hydrothermal reaction, e.g., 175 °C at which no rutile TiO₂ nanorods could grow without the precoated anatase TiO₂ layer. The morphology and microstructure of both the polycrystalline anatase and rutile nanorod layers were characterized by electronmicroscopy and x-ray powder diffraction. Such a two-step fabrication method makes it possible to grow TiO₂ nanorods on almost any substrate.