Oxidation of carbon on nickel-based metallic substrates: Implications for high-temperature superconductor coated conductors

Adhesion of thin films of epitaxial oxides to nickel-based metallic substrates is important for the successful development of high-temperature superconductor coated conductors. Detachment of epitaxial oxide buffer layers at the oxide/metal interface during either oxide growth or subsequent processing renders the conductor useless. In this study, thermal desorption spectroscopy (TDS) has been used to identify and understand one of the causes of buffer layer detachment, oxidation of carbon at the oxide-metal interface to form carbon monoxide. Results of TDS indicate that on the surface of a bare nickel-based alloy substrate, the rate of carbon oxidation depends on both the supply of carbon from the substrate and the supply of oxygen from the vapor. Sulfur at the surface of the alloy substrate reduces the rate of carbon oxidation. The effectiveness of various treatments of the bare substrate to eliminate CO formation and epitaxial oxide detachment has been demonstrated. TDS provides both a means to evaluate the kinetics of the oxidation reaction and a tool to assess the need and effectiveness of a substrate oxidation treatment.