In-situ Epitaxial Growth Of YBCO Thin Films And Its Orientation Controlling

The high quality YBa2Cu3O 7 ??(YBCO)thin films are key materials for various electronic applications. For example, the c-axis orientation are preferred in devices where large transport currents are required to be passed along the film surface; the a-axis orientation are useful in some intrinsic Josephson junctions. Beside of out-of-plane orientation, the in-plane orientation of YBCO is also vitally important to the superconducting properties of YBCO thin films. .In this paper, we employed the Pulsed Laser Deposition (PLD) technique to prepare various out-of-plane oriented films on the single-crystalline MgO (100) substrates, including a-axis films, c-axis films and (103) oriented films, etc., and analyzed the relationship between the deposition conditions and the orientation of films by adjusting of depositing temperature and the pressure of oxygen. Further more, we discussed the mechanism which caused the phase transformation.On the premise of high c-axis orientation, we have also prepared several in-plane oriented films successfully. The in-plane orientation is detected by using XRD pole figure and ? scanning. The results showed that the most YBCO films are eightfold symmetry in the pole figures, which means there are large-angle grain boundaries existed in the films. However, with carefully selection of depositing parameters, it is possible to obtain only fourfold symmetry in the films, where all YBCO grains are arranging in one orientation. We made some interpretations for the mechanism of the in-plane growth,In summary, we have prepared high quality YBCO films, which were textured in both out-of-plane and in-plane by in-situ PLD method. The possible mechanism of in-plane orientation growth was given based on the experimental and interface energy theory.