Fabrication of nanowire-nanotube hybrid arrays in porous aluminum oxide membranes

Fabrication of ordered nanowire-nanotube hybrid arrays embedded in porous anodic aluminum oxide (AAO) membranes is demonstrated. Arrays of TiO$_{2}$ nanotubes were first deposited into the pores of AAO membranes by an electroless sol-gel technique. For subsequent electrochemical deposition of Co nanowires into the TiO$_{2}$ nanotubes, a thick Au layer was first evaporated on one surface of the membrane to serve as the cathode. Co nanowires were then electrochemically deposited into the TiO$_{2}$ nanotubes through the other surface to form the hybrid nanowire-nanotube arrays. SEM and TEM measurements showed a high Co nanowire filling factor and a clean interface between the Co nanowires and the TiO$_{2}$ nanotubes. The TiO$_{2}$ nanotubes were found to be composed of nanometer sized TiO$_{2}$ crystals, while the Co nanowires were polycrystalline with Co crystal size comparable to the nanowire diameter. This technique can be extended to the fabrication of hybrid arrays of various materials. This work was supported by DOE No. DE-FG02-07ER46450, NSF No. DMR-0606529, and the Robert A. Welch Foundation A-0514.