DIRECT OBSERVATION OF THE INTERFACE STRUCTURE OF THIN YBA2CU3OX FILM (LESS-THAN-500 ANGSTROM) DEPOSITED ON SRTIO3(001) UTILIZING GRAZING-INCIDENCE X-RAY-DIFFRACTION

The structure near the interface of thin YBa2Cu3Ox films (<500 Angstrom) deposited on SrTiO3(001) with laser ablation was revealed utilizing grazing incidence x-ray diffraction. The structure consists of a layer with large crystal mosaicity just above the interface, a c-oriented tetragonal layer with lattice constants a=b=3.883+/-0.001 Angstrom, and a well textured but strained orthorhombic layer with lattice constants a congruent to 3.887 Angstrom, b congruent to 3.867 Angstrom in the middle, and a thin air-contaminated top layer. The thicknesses of the differently structured layers determined from x-ray reflectivity data are 50+/-4.7, 20+/-2.2, 200+/-5.5, and 12.56+/-0.14 Angstrom, from the interface to the top layer, respectively. Since there are no additional phases appearing in this system aside from those mentioned, we conclude that the him remains strained at a distance about 300 Angstrom above the interface.