In-plane alignment of a-axis oriented YBa2Cu3Ox thin films

The in-plane orientation of a-axis oriented YBa2Cu3Ox thin films on SrLaGaO4 (100) substrates is studied by φ-scan (in-plane rotation) x-ray diffraction, reflection high energy electron diffraction, and planar-view transmission electron microscopy measurements. It is revealed that the thin films exhibit a twofold symmetry, indicating independent b- and c-axis orientations in the surface plane. There are no 90° domains, and the c-axis of a-axis oriented YBa2Cu3Ox thin films on SrLaGaO4 (100) is aligned to the [001] direction of the substrate azimuth. The resistivity in the c-axis direction at 290 K is 5.5 mΩ cm, about eleven times larger than that in the a-axis direction. The temperature differential of normalized resistivity, d[R(T)/R(300)]/dT, in the c-axis direction (1.1×10−3 K−1) is smaller than that in the b-axis direction (2.8×10−3 K−1).