Structure of epitaxial BiPbSrCuO films grown at low temperatures

Abstract

Bi 2Sr 2Ca n Cu n+1 O 2 n+6 ( n=0, 1, 2) oxide superconductor films have a strong tendency to c-axis-oriented growth, though non- c-axis-oriented films are desirable from a standpoint of coherence length for the layered tunnel junction device applications. Here we examine possibility of non- c-axis-oriented film growth in Bi2201 ( n=0) phase (including Pb-doped Bi2201 (BiPb2201) phase). The reason of the use of these systems is that they have wider stable regions in growth temperature and composition than those of the other two phases ( n=1, 2). For Bi2201 films, only c-axis-orientation was observed irrespective of substrate temperature and substrate orientation. On the other hand, for BiPb2201 films, we found unknown new phase formation at narrow substrate temperatures around 520°C. Film growth direction of this phase is affected by substrate orientation, and the film orientation is presumably to be (0 0 1) on SrTiO 3 (STO) (1 1 0) substrates and (1 0 0) on STO (1 0 0) substrates, which was revealed by means of 4-circle X-ray diffractometory.