Superconducting properties of YNdBaCuO and NdBaCuO thin films deposited by dc sputtering
We report on fabrication of Y/sub 1/Nd/sub x/Ba/sub 2-x/Cu/sub 3/O/sub 7-/spl delta// and Nd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 7-/spl delta// thin films deposited by high oxygen pressure dc sputtering. The structural properties are investigated by X-ray diffraction while Scanning Tunneling Microscopy (STM) has been used to determine the surface morphology. The critical temperature and the critical current density are obtained by transport and inductive measurements. The microwave properties have been studied at 19.8 GHz by a dielectric resonator technique. For both compounds highly epitaxial c-axis thin films are routinely obtained on SrTiO/sub 3/ and LaAlO/sub 3/ substrates. Depending on the deposition conditions, films characterized by surface resistance comparable of even better than YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// have been obtained, with a substantial improvement of the structural properties and of the surface morphology. The role played by the Nd/Ba substitution on the growth and on the superconducting properties is discussed.