“Electron-doped”; (Nd, Ce)2CuO4 (NCCO) superconductor thin films were prepared by post-annealing of metallic double-layer films of Nd(Ce) and Cu deposited onto (001) surface of SrTiO3 (STO) substrates in air at 600 to 1100°C. Cross-sectional high-resolution transmission electron microscopy (HRTEM) was used to observe the microstructure of the films. The formation of NCCO crystallites was observed at the film/STO interface, when the post-annealing temperature was higher than 700°C In spite of epitaxial growth of NCCO at the interface, thin films annealed at 700 to 900°C were polycrystalline. Single-crystalline NCCO films with epitaxial relation to STO substrate were obtained by postannealing between 900 and 1000°C. However, in the film annealed at 1050°C, many planar faults and also some buffer layers at the interface were observed in the NCCO crystals. The film annealed at 1100°C contained no NCCO crystal and a secondary phase was observed. From these findings the mechanism of the film growth is discussed.
