Received: August 30, 2007

In Final Form: October 9, 2007

Abstract:

Free-standing porous anodic alumina (PAA) templates are used for fabrication of dense, uniform, highly ordered, and well-aligned arrays of TiO₂ nanotubes on various substrates, including glass, Si, and flexible polyimide films, via atomic layer deposition (ALD). A large-area free-standing PAA template (>4.5 cm²) is first attached onto the substrate with support of a protective layer of poly(methyl methacrylate) (PMMA) applied on its top. UV-ozone treatment is then employed to completely remove the PMMA layer, keeping the large-area template intact. TiO₂ nanotube arrays with atomic layer control of wall thickness are prepared via ALD on the template. The TiO₂ nanotube arrays with varying wall thickness show size-dependent optical adsorption behaviors. Anatase TiO₂ nanotubes are formed by annealing in air above 300 C. Our method can easily create highly ordered TiO₂ nanotube arrays on a wide range of substrates without causing chemical contamination and changing surface morphology on the substrates. The prepared TiO₂ nanotube arrays show good contact with the substrate, which is of great importance in device applications.

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