Structural variation of the interface-engineered layers in YBa2Cu3O7−δ thin films

Abstract The atomic structures of interface-engineered YBa 2 Cu 3 O 7− δ (YBCO)/plasma-treated YBCO/ a -axis YBCO `trilayer' samples have been observed by transmission electron microscopy. The microstructures are compared by changing the plasma treatment conditions. The detailed structure of the interface or the barrier layer varies both from sample to sample and from place to place in the same sample. It is found that the interface structure depends on both the accelerating voltage and the atmosphere for the plasma treatment. The interfaces under high accelerating voltages (700 and 500 V) are strained, while strain-free barriers with different crystal structures are formed by the treatment under lower accelerating voltages (350 and 200 V). In the sample prepared in the mixed atmosphere of argon and oxygen, a kind of cubic structure is found at the interface, while in the sample fabricated in pure argon, besides the cubic structure, BaCuO 2 and Y 2 O 3 are also observed in the interface.