X-Ray Scattering Studies of the CTR Interference Fringes in YBa₂Cu₃O_7-( Thin Films. W.J.Lin¹, P.D.Hatton¹, F.Baudenbacher², ¹ Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK, ² IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK

The morphology of YBa₂Cu₃O_7-( (YBCO) high-T_c superconducting thin films on SrTiO₃ substrates grown by pulsed laser deposition (PLD) technique have been studied by high resolution x-ray diffraction using synchrotron radiation. Fig.1 shows the crystal truncation rod (CTR) through the (001) thin film reflection. Fringes are clearly observed, which demonstrate the excellent quality of the film, due to the coherent interference between the surface and the interface of the thin film. However, because of the large thickness ((1200(), and the correspondingly large absorption, of the film, the interference fringes are suppressed and these were not found in low angle specular reflectivity scans Fig.2 shows the rocking curve of the (001) thin film reflection. It is clearly found that the peak is composed of a sharp specular reflection, coming from the perfect part of the film, and a broad, weak diffuse scattering, associated with the dislocation distribution. Similar results have been reported in high quality InGaAs/GaAs epilayers (J. Phys.D 28, A133, 1995). Our results demonstrate the excellent crystallography quality of the thin film high T_c oxide that can now be prepared by PLD.