Mobility of electronic charge carriers in titanium dioxide

The present work reports the mobility of electronic charge carriers for well-defined TiO2. The mobility terms were determined by using the electrical conductivity for high-purity TiO2, including both single-crystal and polycrystalline specimens. The concentrations of electronic charge carriers were derived from defect disorder diagrams. The determined data indicate that the transport of electrons and holes occurs according to the band model and the hopping model, respectively. The differences in the electrical conductivity data between the single-crystal and polycrystalline specimens are considered within two scenarios: (1) The difference is due to the mobility terms. This scenario indicates that (i) the mobility of electrons for polycrystalline specimens is larger than that for the single crystal, and (ii) the mobility of electron holes for polycrystalline specimens is smaller than that for the single crystal. (2) The effect is due to the concentration terms. The analysis of data according to this scenario indicates that the concentration of electrons in the n-type regime for polycrystalline specimen is larger than that in the TiO2 single crystal. The mobility and the concentration data are considered in terms of the effect of grain boundaries on the charge transport in polycrystalline TiO2. The obtained data indicate that the charge transport in polycrystalline specimens may be modified in a controlled manner by grain boundary engineering.