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 ∼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.