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

Abstract

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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> 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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C. Although the pellet creates a reaction atmosphere to synthesize the superconducting phase, the fluorine is not incorporated into the quaternary NdFeAsO phase.