DIRECT HIGH-RESOLUTION ELECTRON-MICROSCOPY OBSERVATIONS OF SPUTTERED A-AXIS ORIENTED YBA2CU3O7 FILMS PREPARED BY A SELF-TEMPLATE METHOD ON SRTIO3 SUBSTRATES

A-axis oriented YBa2Cu3O7 films grown on a SrTiO3 substrate with and without the template layer have been studied by high-resolution electron microscopy. The self-template layer was found to be very effective to obtain highly crystalline a-axis oriented YBa2Cu3O7 film. A disordered cubic perovskite structure with a lattice parameter of 3.85 angstrom was found in the template layer which could be a good seed for further growth of a-axis film. In the film without the self-template layer, YBa4Cu3Ox cubic perovskite with lattice parameter 4.08 angstrom was observed to have grown at the interface as an island growth. Moreover, some faulted c-axis film at the very beginning of the template layer was observed even at the rather lower deposition temperature of 640-degrees-C.