Deposition of SDC and NiO-SDC thin films and their surface morphology control by electrostatic spray deposition

The deposition of samaria-doped ceria (SDC, Sm0.2Ce0.8Ox) and NiO-SDC thin films on a SDC substrate was studied using the electrostatic spray deposition (ESD) technique. The precursor solution was prepared by dissolving the correct amount of Sm(NO3)3·6H2O, Ce(NO3)3·6H2O and Ni(NO3)2·6H2O into a mixture of ethanol (C2H5OH) and butyl carbitol (C4H9OC2H4OC2H4OH). The surface microstructure of as-deposited thin films was strongly influenced by the substrate temperature, solvent composition and precursor solution. The reticular film of SDC with high porosity could be successfully prepared at the deposition temperature ranging from 300 to 350 °C, a precursor solution of 0.005 mol/dm3 and a 50 vol.% of butyl carbital. The correlations between the surface morphology of as-deposited thin films and the physical properties of precursor solution could be approximately explained by the following equation [21]:d=G(ε)εε0QK1/3where d is the size of sprayed droplet, Q the flow rate of liquid pushed through the jet, ɛ the dielectric constant of liquid, ɛ0 the electrical permittivity of vacuum, and G(ɛ) is the function of ɛ.The as-deposited thin films were amorphous at the used deposition temperature (350 °C). Subsequently, the thermal treatments were done for ranging from 700 to 900 °C in air. As the result, the crystal structure transformed into the desired cubic fluorite one after the sample was annealed over 700 °C in the as-deposited SDC thin films and 900 °C in the as-deposited NiO-SDC thin films, respectively. To confirm the composition of the as-sintered SDC thin films, ICP-OES analysis was studied for the films annealed at 900 °C in air for 2 h. The observed chemical composition was found to be close to that of the precursor solution within experimental errors.