EXPERIMENTAL-EVIDENCE OF RESPUTTERING OF THE YTTRIA LAYER IN A YBA2CU3O7-X Y2O3 YBA2CU3O7-X TRILAYER FILM

Using transmission electron microscopy and energy dispersive x-ray spe ctroscopy analysis, the microstructure and composition of a YBa2Cu3O7- x/Y2O3/YBa2Cu3O7-x trilayer film deposited on MgO by off-axis sputteri ng at 670-degrees-C and 100 mTorr was investigated. The YBa2Cu3O7-x la yer in contact with the substrate was found to be mainly single phase. However, the top YBa2Cu3O7-x layer was embedded with 5-10 nm crystall ine Y2O3 (yttria) particles, which disturbed the local microstructure. The top YBa2Cu3O7-x layer also had barium copper oxide particles cove ring its surface. The partial decomposition of the top YBa2Cu3O7-x lay er may have been due to resputtering of the yttria layer which locally altered the deposition conditions. In particular, the oxygen pressure in the vicinity of the growing film may have increased due to sputter ing of the yttria layer by plasma gas atoms and the sputtered target a toms. As a result, deposition occurred under conditions away from the thermodynamic stability line.