Measurement of oxygen transport kinetics in epitaxial La2NiO4+δ thin films by electrical conductivity relaxation

The oxygen transport kinetics of mixed ionic and electronic conducting La2NiO4 thin films made by pulsed laser deposition (PLD) were measured using the electrical conductivity relaxation (ECR) technique. Since the film thickness is ∼ 3000 Å, the oxygen transport kinetics are controlled by the surface exchange rate. The experimental data are not well described by the usual single time constant model for oxygen surface exchange, but a good fit is obtained using two independent time constants. This model implies that the La2NiO4 film consists of two independent regions with different exchange rates that correspond to two different film microstructures.