Microstructural evaluation of bilayer film by transmission electron microscopy

The microstructure of SrTiO3/GdBa2Cu3O7-delta bilayer film grown on LaAlO3 substrate was studied by high-resolution transmission electron microscopy (HREM). The results showed that the GdBa2Cu3O7-delta film is epitaxially grown on the LaAlO3 substrate with c axis orientation. Planar defects, grain boundaries, moire patterns, a axis oriented GdBa2Cu3O7-delta and impurity particulates are found in the GdBa2Cu3O7-delta film. The SrTiO3 film was grown on the GdBa2Cu3O7-delta film with a columnar structure. However, some region of the SrTiO3 film is single crystalline, but with strain bands. The development of strain bands in the SrTiO3 film could be a result of lattice mismatch between GdBa2Cu3O7-delta and SrTiO3 films and the surface roughness of the GdBa2Cu3O7-delta film. In consequence, the dielectric properties of the strained STO film are greatly decreased compared to the bulk single crystalline STO.