RuO2 thin films deposited by spin coating on silicon substrates: pH-dependence of the microstructure and catalytic...

RuO(2) thin films have been deposited on Si substrates by spin coating with precursor solutions having a pH varying between 1.4 and 4. X-ray diffraction and transmission electron microscopy analyses are used to determine correlations between the solution pH and the film microstructure. As the pH varies, the RuO(2) crystal sizes reach a minimum value then increase; the porosity increases at the substrate/film interface with formation of large cavities. The catalytic activity of these RuO(2) layers in the presence of flowing air-methane is analysed by Fourier transform infrared spectroscopy of the conversion of CH(4) into CO(2). The increasing porosity seems to improve the catalytic conversion rate of methane. Electrical impedance spectroscopy analyses show that the conductivity strongly depends on the thin-film microstructure and porosity.