XRD and TEM characterization of cuprate thin films epitaxially grown on SrTiO₃ (0 0 1) vicinal surfaces

We report X-ray diffraction and transmission electron microscopy of YBa₂Cu₃O₇ (YBCO) and NdBa₂Cu₃O₇ (NBCO) thin films grown by pulsed laser deposition on SrTiO₃ (0 0 1) vicinal surfaces (SrTiO₃, STO). Most YBCO films tend to grow parallel to the geometrical surface: YBCO (0 0 1) planes are parallel to the substrate surface rather than to STO (0 0 1) planes. On the contrary, NBCO tends to follow the STO (0 0 1) planes. The tetragonal to orthorhombic phase transition upon cooling induces twinning in both materials. The twins appear to have better defined interfaces in YBCO than in NBCO. While the two twin variants [1 1 0] and [1 1̄ 0] are present in YBCO, only one occurs in NBCO films. This selectivity of twin orientation might be useful in device applications.