Template-Based Electroless deposition and TEM Analysis of TiO$_{2}$ Nanotubes*

We report on the fabrication of TiO$_{2}$ nanotubes using a template-based electroless deposition method. We used anodic aluminum oxide membranes of pore diameter $\sim $ 200 nm as the templates. The TiO$_{2}$ nanotubes were fabricated by first dipping the membranes into a titanium tetrafluoride solution at 60 \r{ }C for 30 minutes, and then annealing at 225 \r{ }C for 2 hours. The composition of the nanotubes was verified using the energy dispersive spectroscopy. We used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study the surface morphology of the nanotubes extracted after the membranes were dissolved. The nanotubes were found to be uniform along the length of the nanotube. For TEM analysis, an ion-milling technique was also used to produce a thin sample region so that the cross-section of the nanotubes remaining in their original pore channels could be directly imaged. The thickness of the TiO$_{2}$ nanotubes is about 50 nanometers, and could be controlled by varying the deposition time. Potential applications of these semiconducting TiO$_{2}$ nanotubes for forming nanostructured semiconducting interfaces will be discussed.