Electrical properties of Schottky diodes on nano-porous TiO2 films

We have studied the electrical transport properties of nano-porous TiO2 films in laboratory air and dry nitrogen ambients. For the Pt/TiO2 Schottky barrier we find a barrier height of 1.7 eV, compatible with an electron affinity of 3.9 eV for the TiO2 films. Below similar to 300 K, tunneling transport through the barrier occurs, resulting in strong barrier lowering. The barrier lowering becomes more severe with increasing humidity, indicating that water adsorption induces a large surface state density. Time-resolved photoconductance decay measurements show that water adsorption also leads to a reduction of the electron drift mobility and the photoconductance. (C) 2000 Elsevier Science S.A. All rights reserved.