The microstructures of superconducting thin films, epitaxially grown onto symmetrical or asymmetrical 45° cubic ceramic bicrystalline substrates were investigated by means of transmission electron microscopy. The grain boundary of the asymmetrically tilted SrTiO3 substrate was straight, with a single (110)/(100) facet, while that of the symmetrical 45° bicrystalline substrate was wavy and contained many asymmetrical step-like (110)/(100) nanofacets. The grain boundaries of the superconducting films grown onto such symmetrical 45° bicrystalline SrTiO3 substrates were composed of only (110)/(100) facets and therefore meandered. All of the results indicated that the interfacial energy of asymmetrical (110)/(100) was lower than the symmetrical configuration (250)/(520) in the SrTiO3.

Microstructural Relationships between 45° [001] Tilt Bicrystal Substrates and Epitaxial Superconducting Films. Y.Wu, N.Inoue, T.Sugano, S.Adachi, K.Tanabe, N.Koshizuka, J.G.Wen: Physica C, 2001, 361[3], 221-6