Ba2YCu3O7−δ crystal surface layers: Orthorhombic splitting, dislocations, and chemical etching

Abstract We find by transmission electron diffraction that the orthorhombic splitting of the upper surface layers ( 2 YCu 3 O 7− δ is reduced, differing by 10 to 30 percent from the bulk value. We also find by transmission electron microscopy that in general the surfaces are of inferior quality and, thus, not representative of the bulk. These results have important consequences for those experiments that probe only the upper surface layers. By etching with Br/ethanol and HClO 4 /NaClO 4 the poor quality surfaces are removed.