In-plane anisotropic transport properties observed in epitaxial Bi2(Sr,Ca)3Cu2Ox films grown on tilted (001)SrTiO3 substrate

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Abstract
We report on large in‐plane anisotropic transport properties observed in epitaxial Bi2(Sr,Ca)3Cu2Ox films grown on tilted (001)SrTiO3 substrate. By tilting the surface normal axis about 4° toward [111]SrTiO3, regular steps and terraces were formed on the substrate surface and perfect alignment of film b axis with incommensurate modulation along [110]SrTiO3 was realized. The film c axis was perpendicular to the (001)SrTiO3 terrace, thus the film c axis grew tilted 4° toward [111] from surface normal due to the surface inclination. In those epitaxial configurations, the in‐plane resistivity along the step direction(ρ[110]) involved the contribution from the c‐axis(ρc) component, and we observed the large resistivity anisotropy between a‐ and b‐ direction of the film. The transport along a axis(ρa) showed a low resistivity with metallic temperature dependence while the resistivity along the step direction(ρ[110]) was higher and semiconductive. The ratio of ρc/ρa ≊ 104 estimated in this experiment agrees well with the anisotropy observed in the bulk single crystal.