Orthorhombic splitting and chemical etching of Ba2YCu3O7-δ crystal surfaces

The authors find by transmission electron diffraction (TED) that the orthorhombic splitting of the upper surface layers (<1 μm) of single crystal Ba2YCu3O7-δ (YBCO) is reduced, differing by 10 to 30 percent from the bulk value. They also find by transmission electron microscopy (TEM) 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 either Br/ethanol or HclO4/NaClO4 the poor quality surfaces can be removed