Forty-five degree oriented YBa₂Cu₃O_7−x/MgO interface structures studied by high-resolution electron microscopy

Abstract

Films of YBa 2 Cu 3 O 7Àx (YBCO) grown on (001) MgO substrates by liquid phase epitaxy in an oxygen atmosphere were investigated by high-resolution electron microscopy. The in-plane orientation of the films with respect to the substrates was [110] YBCO //[100] MgO . Two kinds of interface structures were observed from high-resolution electron microscope images. It was determined that in one kind of interface structure the initially formed layer of YBCO on MgO is the CuO layer, while in the other it is the BaO layer followed by a CuO layer. In the latter case, a thin layer of Cu 2 O is first formed on MgO as a linkage between YBCO and MgO.

Intrinsic structure and thermal stability of YBCO thin film

“…Figure 4(a) shows the HRTEM image of the atomic configuration in the vicinity of the interface between film B and the MgO substrate, and the inset displays the diffraction pattern showing that the in-plane epitaxial orientation is 45 • . The amplified part from the interface, as shown in figure 4(b), indicates that there are two unexpected rows of atoms between MgO and the BaO-CuO-BaO blocks of Y123, which is deduced to be the Cu 2 O phase [20]. This HRTEM work revealed that the terminal layer of film B (45 • oriented) is Cu 2 O, which does not belong to the YBCO lattice.…”