Effect of chemical and ion-beam etching on the atomic structure of interfaces in YBa2Cu3O7/PrBa2Cu3O7 Josephson junctions

Abstract

The atomic structure of the interfaces of Josephson junctions formed by epitaxial YBa2Cu3O7/PrBa2Cu3O7/YBa2Cu3O7 triple-layer films was investigated by high-resolution transmission electron microscopy. The samples were fabricated by sputter deposition on surfaces which were etched ex situ either chemically, using a nonaqueous Br-ethanol solution, or by an Ar ion beam. In the interfaces produced after ion etching a thin intermediate layer with a thickness of a few nanometers was observed. The main part of this layer consists of cubic PrBa2Cu3O7 or YBa2Cu3O7 which is cation disordered. The interfaces formed during deposition on Br-ethanol-etched surfaces did not contain such an intermediate layer but exhibited high structural perfection similar to that of interfaces produced in situ. These observations permit a qualitative explanation of the difference in the electrical properties of junctions produced by these two techniques.