Growth of high-quality YBa2Cu3O7−x films on CeO2 buffer of mixed (001)/(111) orientation on sapphire
- 30 October 1995
- journal article
- research article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 67 (18) , 2723-2725
- https://doi.org/10.1063/1.114305
Abstract
High‐quality epitaxial YBa2Cu3O7−x (YBCO) thin films are grown on large area (1ub;‐21ubx02) sapphire (r‐cut) substrates buffered by CeO2 of mixed (001) and (111) orientation. It is shown that (001) and (111) CeO2 epitaxy on (1ub;‐21ubx02) sapphire is possible with further growth of well‐oriented (001) YBCO on both orientations of CeO2. In the case of (111) CeO2 one of the equivalent in‐plane trigonal directions, i.e., [10ub;‐21ubx], [ub;‐21ubx10], or [01ub;‐21ubx], is aligned along either [02ub;‐22ubx1], or [2ub;‐22ubx01] crystallographic axis of sapphire, which is indicated by the φ‐scan x‐ray diffraction pattern of the (115) CeO2 reflex. The resulting (001) YBCO film grown on the (001)/(111) CeO2 buffer reveals no disorientations in the a‐b plane other than conventional 90° twinning. The YBCO films exhibited very smooth surface and were free of screw dislocations. The high quality of the YBCO films is confirmed by the microwave surface resistance of Rs≤0.44 mΩ at 10 GHz and 77 K.Keywords
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