Fabrication of superconducting Nd2−xCexCuO4±δ films by automated dc sputtering technique

Abstract

Superconducting electron-doped Nd2−xCexCuO4±δ films have been successfully prepared on (001) SrTiO3 substrates by an automated dc sputtering system. The composition of the samples has been measured by wavelength dispersive spectroscopy, and the crystalline structure has been investigated by high resolution X-ray diffraction technique. Measurements by backscattered electrons has been also used in order to deeply analyze the microstructure of the samples. We have found that the quality of the films is highly sensitive to the deposition conditions and that the superconductivity is reached only after suitable heat treatments at temperature above to 850°C in an oxygen-reducing atmosphere. The films deposited with the optimized conditions show a high degree of epitaxial growth, moreover an increase of c lattice parameter is found in all the superconducting samples. X-ray reflectivity measurements on thin films by using synchrotron radiation proved that smooth surfaces (roughness less than 2nm) and neat interfaces characterize the films through the whole thickness.