Growth of NdFeAsO Films by a Combination of Metal–Organic Chemical Vapor Deposition and Arsenic Diffusion Processes

NdFeAsO films have been grown by a two-step method. First, precursor films that contain a mixture of Nd and Fe oxides were grown by metal-organic chemical vapor deposition. Afterward, the arsenic is incorporated during annealing of these precursor films in the presence of a NdFeAsO_0.75F_0.25 pellet. The X-ray diffraction and the scanning electron microscopy show that the formation of the quaternary NdFeAsO phase is prevented by the stability of the rare-earth oxides and rare-earth oxyfluorides and that it is synthesized only if the annealing temperature is higher than 1050 ^°C. Although the pellet creates a reaction atmosphere to synthesize the superconducting phase, the fluorine is not incorporated into the quaternary NdFeAsO phase.