SEMICONDUCTING PROPERTIES OF UNDOPED TIO2

Both electrical conductivity and thermopower were studied for undoped [001] oriented TiO2 single crystals within the temperature ranges 985- 1387 K and oxygen partial pressure 10(-15)-10(5) Pa. Using a Jonker-ty pe analysis the energy gap in TiO2 was determined (E-g = 3.09-1.33 x 1 0(-3) T/eV). It was shown that the transport of both electrons and ele ctron holes occurs according to the small polaron model. The electrica l properties determined in this work indicate that below and above 130 0 K, respectively, the predominant defects in TiO2 are doubly ionised oxygen vacancies and interstitial Ti4+ ions. (C) 1997 Elsevier Science Ltd.