Previous studies had shown that there was always an appreciable resistive tail below the bulk Tc value of EuBa2Cu3O7−δ and SmBa2Cu3O7−δ (RBCO) films deposited onto nearly perfect lattice-matched SrTiO3 substrates. This contrasted with the same films when deposited onto less well-matched substrates, such as LaAlO3, under similar conditions. Although the lattice match was poorer, these films exhibited a sharp resistive transition without any tail. The present work examined the evolution of precipitate density and intergranular coupling with increasing film thickness. This revealed that dislocations introduced by the release of strain affected the precipitation of off-stoichiometric phases. A model was proposed that indicated that such dislocations attracted off-stoichiometric phases and led to tower-like precipitates. These segregated potential impurities from grain boundaries. Thus, intergranular coupling of RBCO films grown onto LaAlO3 improved with increasing thickness. In the absence of precipitates, off-stoichiometric materials – present in the films on SrTiO3, coated each columnar grain.

Substrate Strain Effect of EuBa2Cu3O7-δ Film - Interplay between Dislocations, Precipitates and Superconductivity. Y.C.Liao, M.K.Wu, C.C.Chi: Physica C, 2004, 416[3-4], 95-107