Chemical bath deposition of IrO2 films on ITO substrate

Abstract A chemical bath is shown to deposit an IrO 2 film on an ITO substrate. The chemical bath is prepared by mixing an Ir precursor (Na 3 IrCl 6 · x H 2 O), an oxidizer (NaClO), a complexing agent (NaNO 2 ), 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 ) 4 Cl 2 ] 3− , and [Ir(NO 2 ) 3 Cl 3 ] 3− are identified. These complexes are relatively stable, minimizing the undesirable homogeneous precipitation of IrO 2 nanoparticles in favor of the heterogeneous growth of the IrO 2 film on the ITO substrate. Diffraction patterns from the as-deposited IrO 2 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 IrO 2 film is +4. Thermogravimetric analysis confirms the inclusion of 10 wt% hydrated water in the as-deposited IrO 2 film. Scanning electron microscope images reveal a continuous solid film with a smooth surface. The amorphous IrO 2 film becomes rutile IrO 2 phase after a mild heat treatment in air.