MESOSCOPIC-RANGE ORDER IN AMORPHOUS BIPBSRCACUO FILMS AND ITS EVOLUTION DURING CRYSTALLIZATION

Atomic structure and conductivity of amorphous and crystalline films p repared by cathode sputtering of Bi-2223 targets onto (100) MgO substr ates were studied in the range of substrate temperatures t(s) between 20 and 450 degrees C. The clusterized, mesoscopic-scale structure of a morphous films is metastable; its crystallization may yield a wide ran ge of structures, depending on t(s) and annealing temperature. In the amorphous films, the clusters are composed of (11l)perovskite layers d eficient in Cu-O planes, which results in the formation of two-phase c rystalline films. Crystallization at low temperature (460 degrees C) f avors orientations typical of clusters, while high-temperature anneali ng (865 degrees C) yields (001)-oriented films exhibiting superconduct ing transition at T-c = 110 K.