Physicochemical characterization of sputtered iridium oxide

In the present work we characterize sputtered iridium oxide films (SIROF) by differential scanning calorimetry (DSC), x-ray, and impedance spectroscopies. We show that a crystallization transition occurs at ca, 230 °C, and suggest a bilayer model for the sputtered film. The transition results in a crystalline mixture of iridium metal and iridium oxide; this suggests a decomposition-crystallization process of the type 2Ir2O3 ⇉ Ir + 3IrO2. In the bilayer model proposed by us, the layer closer to the substrate would reflect the combined influence of the sputtering conditions and of the substrate, while the properties of the second layer depend on the sputtering conditions alone. The bilayer structure is supported by results obtained by impedance spectroscopy.