Synthesis and variable temperature electrical conductivity studies of highly ordered TiO2 nanotubes

Abstract

Rafts of aligned, high aspect ratio TiO 2 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 µm, 160 nm and 30 nm, respectively. Transmission electron microscopy studies confirmed that the TiO 2 nanotubes were initially amorphous, and became polycrystalline anatase after heat treatment at temperatures as low as 250 °C 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.

Nanotubular Cr-doped TiO 2 for use as high-temperature NO 2 gas sensor

“…This potential barrier arises due to trapping of electrons by pre-adsorbed oxygen and subsequently developing a depletion region on the surface [35,36]. This is noticeable in our measurement that Cr-doped TiO 2 NTs showed higher values of resistance R=≈800 MΩ than R=≈5 kΩ of un-doped TiO 2 NTs at 500 °C.…”

“…7 (bottom). In contrast, the thinner depletion layer will yield larger potential barrier height with at the temperature range of 250°C -350°C which may be controlled by oxygen partial pressures [36,37]. Depending on the oxygen partial pressure, activation energies E A for nanocrystalline TiO 2 were reported to be E A =0.85 eV for the pressure range 1 mbar<p(O 2 )<10 3 mbar, as well as E A =0.013 eV at p(dry air)=4×10 −6 mbar, E A =0.31 eV at p(dry air)=1 mbar and E A =0.69 eV at p(dry air)=10 mbar [37,38].…”

Organometallic Titanium Oxides Obtained by Low-Pressure Plasmas of Water on Titanium Tetrapropoxide

“…[1] H. Porthault, ger, "Synthesis of LiCoO 2 Thin cess," Journal of thermally activated at 300˚C was calculated as 10 −6 S/m, with activation energy of 0.87 eV [18]. In TiO films, conductivity was calculated as 10 −9 S/m with activation energy in the 0.76 -1.55 eV interval [19].…”

Influence of the size-controlled TiO2 nanotubes fabricated by low-temperature chemical synthesis on the dye-sensitized solar cell properties

“…For high photovoltaic performance of DSSC, there have been significant research efforts to discover the nature of this device, which usually consists of anode electrode materials, sensitized dye, electrolyte, and counter electrode. Because anode electrode materials require nanoscale and highly crystalline semiconductors with large surface area for the adsorption of sensitized dyes, various one-dimensional (1D) nanostructured TiO 2 materials such as nanowire [5], nanorod [6][7][8][9][10], and nanotubes [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] have gained much attention.…”

“…In general, TiO 2 NTs are synthesized for the electrodes of DSSC by the electrochemical anodic oxidation method [3,8,[11][12][13] or the low-temperature chemical synthesis route [2,14], and their various tailoring structures and morphological features were investigated and determined depending on their method of synthesis. Vertically oriented TiO 2 NT arrays made by anodization of titanium in fluoride-based baths have precisely oriented nature of the NT array and excellent electron percolation pathways.…”