Figure 5. Applying a voltage across the film/substrate interface.

Measurements of the average conductance between electrodes 1 and 7, plotted versus time when a voltage is applied between electrodes 4 and 4b using a battery (see Fig. 1 for the electrode configuration). Region (a): Applying 1.6 V, with the film at a higher potential than the substrate, moves oxygen ions from YSZ into the In₂O₃. This reduces the oxygen vacancy doping of the film, thus reducing the measured conductance. Region (b): When the battery is open-circuited, the conductance relaxes towards the initial value as the film's oxygen vacancy concentration returns to the equilibrium value determined by the temperature and pO₂. Region (c): Applying 1.6 V, with the substrate at a higher potential than the film, moves oxygen ions from In₂O₃ into the YSZ. This oxygen vacancy dopes the film, thus increasing the measured conductance. Region (d): Removing the battery again results in the measured conduction relaxing towards the starting value as the film oxygen vacancy concentration returns to that set by the temperature and pO₂. The measurements were taken at 330 °C with pO₂=1.5 torr.