Epitaxial growth study of Bi2(Sr,Ca)3Cu2Ox films on cleaved MgO substrates

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Abstract
In situ epitaxial growth of Bi2(Sr0.6Ca0.4)3Cu2Ox films by ion beam sputtering on cleaved MgO substrates was studied. The crystallographic structures were analyzed by in situ reflection high‐energy electron diffraction, a four‐circle x‐ray diffractometer, and a scanning electron microscope. While the epitaxial films on polished MgO substrates commonly showed the fourfold symmetry, epitaxial films having twofold symmetry were grown on cleaved MgO substrates and the films contained two types of equivalently misoriented domains. The epitaxial relationship between these domains and cleaved MgO substrates was such that the b axis of each domain deviated approximately ±13° from [010]MgO where the cleavage steps ran along [100]MgO. The step edges seemed to play an important role in the occurrence of the twofold epitaxial relationship, where the incommensurate modulation tended to align its direction so as to avoid the step edges.