Chemical bath deposition of IrO₂ films on ITO substrate

A chemical bath is shown to deposit an IrO₂ film on an ITO substrate. The chemical bath is prepared by mixing an Ir precursor (Na ₃IrCl₆·xH₂O), an oxidizer (NaClO), a complexing agent (NaNO₂), and a complex agent/stabilizer (NaOH) in an aqueous solution at a molar ratio of 1:1.5:10:30. From the UV-vis absorption spectra, complexes such as [Ir(OH)₆]m^3-, [Ir(NO ₂)₄Cl₂]^3-, and [Ir(NO ₂)₃Cl₃]^3- are identified. These complexes are relatively stable, minimizing the undesirable homogeneous precipitation of IrO₂ nanoparticles in favor of the heterogeneous growth of the IrO₂ film on the ITO substrate. Diffraction patterns from the as-deposited IrO₂ film reveal an amorphous structure. In addition, profiles from X-ray absorption spectroscopy and X-ray photoelectron spectroscopy indicate that the oxidation state of the Ir in the as-deposited IrO₂ film is +4. Thermogravimetric analysis confirms the inclusion of 10 wt% hydrated water in the as-deposited IrO₂ film. Scanning electron microscope images reveal a continuous solid film with a smooth surface. The amorphous IrO₂ film becomes rutile IrO₂ phase after a mild heat treatment in air.