Transport anisotropy of in-plane c-axis aligned a-axis oriented YBa₂Cu₃O_x thin films

The temperature dependence of resistivity, ρ{variant}_b and ρ{variant}_c, is measured for a perfectly in-plane c-axis aligned a-axis oriented YBa₂Cu₃O_x thin film. In-plane alignment of the film is confirmed by X-ray ø-scan (in-plane rotation) diffraction and reflection high-energy electron diffraction (RHEED) measurements. X-ray ø-scan measurements and RHEED patterns reveal that the thin film has a twofold symmetry with no 90° domains, showing the c-axis for the film is aligned in-plane. Resistivity-temperature curves for both c- and b-directions show metallic behavior with a T_C of 90.5 K. Resistivity in the c-axis direction at 290 K is 5.5 mΩcm, which is about eleven times larger than that of 500 μmΩcm for the b-axis direction. The resistivity anisotropy is in the same order as the coherence length. The temperature differential of normalized resistivity, d(ρ{variant}(T)/ρ{variant}(300))/dT, in the b-axis direction (2.8x10^-3/K) is 2.5 times larger than that in the c-axis direction (1.1x10^-3/K). This result clearly shows that the carrier transport in the b-axis direction is more metallic than that in the c-axis direction.