Structural characterization of a-axis oriented YBa₂Cu₃O_x films grown by liquid phase epitaxy

YBa₂Cu₃O_x films on low-misfit La_xNd_1-xGaO₃ (110) substrates grown by liquid phase epitaxy (LPE) are investigated in the as-grown state by X-ray diffraction, polarized optical microscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM). The preferred orientation axis of the film normal to the substrate surface is the a-/b-axis with twins, as observed by θ/2θ-scan, polarized optical micrographs, and cross-sectional view TEM images. In-plane alignment of the c-axis in the films is confirmed by X-ray φ-scan and plane-view TEM images. Defects running perpendicular to the c-axis direction were clearly observed in the plane-view TEM images. These defects consist of excess CuO chains localized in the BaO-BaO interlayers forming (CuO)_n layers, similar to that in Y₂Ba₄Cu₈O_x (248 phase).