THE DIRECT EVIDENCE OF MICRO-TWINNINGS IN YBA2CU3O7-X THIN-FILMS FROMSURFACE X-RAY-DIFFRACTOMETRY

The first direct evidence of micro-twinnings in laser-ablated YBa2Cu3O 7-x thin films has been found using a high-resolution surface X-ray di ffractometer. The superconducting films were epitaxially grown by lase r ablation and their c-axes were perpendicular to the (100) SrTiO3 sub strate surfaces. The (308) and (038) peaks of the YB2Cu3O7-x thin film s were resolved quite clearly in rocking curves of the peaks, for the first time to our knowledge, to show that the films are twinned along the {110} directions on a microscopic scale. The experimental data of these twinned peaks, which are in excellent agreement with the theoret ical calculations, are presented, and the effect of the micro-twinning structure of the thin films on the X-ray diffraction intensity is dis cussed.