Abstract
Rafts of aligned, high aspect ratio TiO2 nanotubes were fabricated by an electrochemical anodization method and their axial electrical conductivities were determined over the temperature range 225-400 °C. Length, outer diameter and wall thickness of the nanotubes were approximately 60-80 ∝m, 160 nm and 30 nm, respectively. Transmission electron microscopy studies confirmed that the TiO2 nanotubes were initially amorphous, and became polycrystalline anatase after heat treatment at temperatures as low as 250 ϒC in air. The activation energy for conductivity over the temperature range 250 - 350 °C was found to be 0.87 eV. The conductivity values are comparable to those of nanocrystalline and nanoporous anatase thin films reported in literature.
Highlights
Titania is of tremendous interest for applications in photovoltaic devices such as solar cells[1,2] photo-catalysis[3,4] and photo-electrochemistry[5]
Titania is a key component of the dye-sensitized solar cell (DSSC)
In Figure 1 we present field emission scanning electron microscope (FESEM) images of
Summary
Titania is of tremendous interest for applications in photovoltaic devices such as solar cells[1,2] photo-catalysis[3,4] and photo-electrochemistry[5]. In several of these technological applications, understanding the temperature dependent conductivity is critical for understanding device performance, as well as to extract fundamental information on conduction mechanisms and activation energy for carrier transport.[10] To the best of our knowledge, this paper presents the first electrical conductivity measurements of titania nanotubes. After the anodization was complete, the TiO2 nanotubes, which comprised yellow flakes on both sides of the Ti foil, were washed with isopropyl alcohol and immersed in a diluted HCl (0.1 M) solution for 1 hr.
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