Surface and interface structure of Nd1.2Ba1.8Cu3Oy epitaxial films studied by grazing incidence X-ray diffraction

High quality, very flat Nd1.2Ba1.8Cu3Oy thin films have been grown by sputtering on TiO2 terminated SrTiO3 (100) single crystals and their surface structure have been determined by using Grazing Incidence X-ray Diffraction (GIXD) technique, employing synchrotron radiation. A 52 unit cells film presents a double terminated surface composed by a complete and ordered Cu(1)-O plane and a disordered Cu(1)-O plane partially covered by a BaO layer, in full agreement with scanning tunneling microscopy data. A preliminary comparison between the structure of 8 and 52 u.c. NdBCO films will be presented.