Temperature- and oxygen partial pressure-dependent electrical conductivityin nanoporous rutile and anatase

The dependence of the electrical conductivity (sigma) of sintered nanoporou s TiO2 (rutile and anatase) layers on temperature (T) and partial pressure of oxygen (p(O2)) has been studied by impedance spectroscopy for T up to 45 0 degrees C and p(O2) up to 10(-5) mbar. The diameter of the TiO2 nanoparti cles was changed between 5 and 60 nm. sigma is thermally activated with E-A =0.85 eV independent of the absolute value of sigma and depends on p(O2) by power law for p(O2)< 1-10 mbar. The electrical properties of reduced nanop orous TiO2 are determined by surface chemical reactions which lead to the f ormation of shallow donor and deep trap states. (C) 1999 American Institute of Physics. [S0003-6951(99)03551-2].