Growth of untwinned Bi2Sr2Ca2Cu3Ox thin films by atomically layered epitaxy.

We report the growth of untwinned epitaxial thin films of Bi-Sr-Ca-Cu-O by atomically layered heteroepitaxy on SrTiO3 substrates. These films are c-axis oriented as-layered and do not exhibit 90° in-plane defects, i.e., a-b ‘‘twinning.’’ By misorienting the surface normal from {100} by approximately 4° towards <111>, the cubic symmetry of the {100} surface is adequately broken to completely align the b axis of the superconducting film with respect to the substrate. Reflection high-energy electron diffraction patterns observed during growth and post-growth x-ray diffraction analysis indicate that the incommensurate structural modulation occurs along the same direction as the step edges. [ABSTRACT FROM AUTHOR]