Two-dimensional superstructure in the (001) plane of Bi2[Ca,Sr]3Cu2O8+δ thin films

Abstract
Thin films of Bi‐Ca‐Sr‐Cu‐O showing superconductivity above 100 K have been made by electron beam evaporation with oxygen post‐annealing. The major superconducting phase, Bi2[Ca,Sr]3Cu2O8+δ (Tc ∼85 K), is oriented epitaxially with the (100)SrTiO3 substrate. In addition to the one‐dimensional incommensurate superstructure along the b axis, which is characteristic of this phase, we have observed by transmission electron microscopy a two‐dimensional incommensurate superstructure in the ab plane with a different periodicity and a different orientation relationship to the subcell.