In-plane orientation of c-axis-oriented Bi2Sr2Can−1CunO2n+4+δ thin films on Nd:YAlO3 substrates

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Abstract
In‐plane orientation of thin‐film Bi2Sr2Can−1CunO2n+4+δ superconductors on Nd:YAlO3 is investigated in detail. Thin films of c‐axis‐oriented Bi2Sr2Can−1CunO2n+4+δ are grown in situ by molecular beam epitaxy with pure ozone as an oxidant. The in‐plane orientation of the films was observed by reflection high‐energy electron diffraction. A characteristic epitaxial relationship was found between Bi2Sr2Can−1CunO2n+4+δ (001) and Nd:YAlO3 (001), and as a result, Bi2Sr2Can−1CunO2n+4+δ was grown without the a‐b twinning structure, maintaining the relation Bi2Sr2Can−1CunO2n+4+δ [010] ∥Nd:YAlO3[100]. This relationship is found to be independent of the phases (n) of the films. Moreover, it is affected by the steps running parallel to Nd:YAlO3 [100]. With increase of the step density by changing the misorientation angle from (001) toward [010], the in‐plane orientation of Bi2Sr2Can−1CunO2n+4+δ is rotated by 90° around its c‐axis direction. The epitaxial relationship is discussed with respect to the anisotropic growth rate of Bi2Sr2Can−1CunO2n+4+δ films.