Fluctuation-Induced Tunneling Conductivity in Nanoporous TiO2 Thin Films
SJ Konezny and C Richter and RC Snoeberger and AR Parent and GW Brudvig and CA Schmuttenmaer and VS Batista, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 2, 1931-1936 (2011).
The electronic mechanisms responsible for dark conductivity in nanoporous TiO2 thin films remain only partially understood, although they control the efficiency of charge transport in a wide range of technological applications. Measurements in the 78-335 K temperature range show DC conductivity values spanning over 4 orders of magnitude, with a high-temperature Arrhenius dependence that gradually changes into a temperature-independent plateau at low temperatures. We show evidence that a fluctuation-induced tunneling conductivity (FITC) mechanism is fully consistent with the experimental data. Quantitative agreement is demonstrated for the entire temperature range (T = 78-335 K) with a FITC model parametrized according to atomistic models of nanoporous TiO2 and the characterization of the films by X-ray diffraction and scanning electron microscopy measurements. These findings suggest that dark DC conductivity in nanoporous TiO2 films depends strongly on the properties of the junctions linking the constituent nanoparticles.
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