Substrate dependence of the deposition behavior of CeO2 buffer layer prepared by MOCVD method

Buffer layers such as CeO2 and Yb2O3 films for YBCO coated conductors were deposited on (100) SrTiO3 single crystals and (100) textured Ni substrates by a metal organic chemical vapor deposition (MOCVD) system of the hot-wall type. The substrates were moved with the velocity of 40 cm/hr. Source flow rate, Ar/O2 flow rate and deposition temperature were main processing variables. The degree of film epitaxy and surface morphology were investigated using XRD and SEM, respectively. On a STO substrate, the CeO2 film was well grown epitaxially above the deposition temperature of 450 degrees C. However, on a Ni substrate, the XRD showed NiO (111) and (200) peaks due to Ni oxidation as well as (111) and (200) film growth. For the films deposited with O2 gas as oxygen source, it was found that the NiO film was formed at the interface between the buffer layer and the Ni substrate. The NiO layer interrupts the epitaxial growth of the buffer layer. It seems that the epitaxial growth of the buffer layer on Ni metal substrates using O2 gas is difficult. We are considering a new method avoiding Ni oxidation with H2O vapor instead of O2 gas.