Atomic structures of surface and interface in (Hg,T1,Pb)-based superconductors studied by high-resolution electron microscopy

Atomic structures of surface and interface in (Hg,Tl, Pb) -based superconductors were investigated by high-resolution electron microscopy. The interfaces observed in TI-based superconductors have the disordered region with similar to 1 nm thickness, which would be suitable for barrier layers for tunneling junctions. Although the {001} planes of (Hg,Tl)-based oxides are fairly stable, most of the {100} planes are unstable, and atomic rearrangement was often observed. However, the HREM image of Hg0.5Tl0.5Ba2CuO5 {100} showed the stable Ba-O-Ba layer at the surface, and oxygen atom positions were determined. The present study indicates that the surfaces of the Hg- and TI-based superconductors are strongly dependent on the crystallographic planes and crystal structures. (C) 2002 Elsevier Science Ltd. All rights reserved.