Effective removal procedure of residual carbon in CeO2−x films fabricated via MOD method

Abstract

The influence of annealing atmosphere with different CO2 concentrations on the texture and morphology of CeO2−x films grown on bi-axially textured Ni–W substrates by metal-organic deposition (MOD) method has been investigated and the optimal film processing condition to achieve residual carbon removal in CeO2−x buffer layer has been determined. We have found that the CeO2−x films fabricated in Ar–4% H2 with less than 5% CO2 have strong c-axis texture and high crystallinity. However, a few of micro-cracks and even some large grains are observed on the surface of CeO2−x films annealed in annealing atmosphere with high CO2 content due to the variation of tensile stress and accumulation of carbonate. The CeO2−x film fabricated in (Ar–4% H2)–0.5% CO2 displays a moderate improvement in out-of-plane texture as compared to the substrate texture. And it shows a smoother and denser surface morphology as well as a smaller grain size in comparison to the CeO2−x prepared in Ar–4% H2. The sharper drop of C signal of CeO2−x film grown in (Ar–4% H2)–0.5% CO2 than that prepared in Ar–4% H2 points to an effective removal procedure of residual carbon by introducing CO2 to annealing atmosphere. The present results demonstrate a viable approach for the production of high-quality buffer layer with little residual carbon for coated conductors.