Structural study of electrochemically synthesized TiO2 nanotubes via cross-sectional and high-resolution TEM

The as-grown structure of electrochemically synthesized titania nanotubes is investigated by a combination of cross-sectional and high-resolution transmission electron microscopy (TEM). The analysis reveals a preferred growth direction of the nanotubes relative to the substrate surface and the presence of a thin barrier oxide layer that exists between the metal substrate and the nanotubes. High-resolution TEM images also provide information about the morphology of the metal/oxide and oxide/nanotube interfaces, and the crystallinity of the different layers. In addition, compositional analysis performed via energy dispersive X-ray spectroscopy (EDS) indicates that there are differences in oxygen and titanium concentrations between nanotubes and barrier oxide. The experimental observations obtained from these analysis techniques provide additional insights about the tube formation process.