Non-orthogonal twinning was observed in thin films of oxide perovskites. This twinning geometry was equivalent to a 60 rotation of the twinned crystallites about the [111] direction in an [001]-oriented film. This twinning could not be detected by using standard X-ray tests of film quality. Here, the twinning was observed in films which had been grown by sputtering and metalorganic chemical vapor deposition onto MgO and SrTiO3. The twins were observed in films that had been deposited onto a substrate for which there was a large lattice mismatch, and in films that had been deposited in an O-deficient ambient. It was proposed that these twins resulted from a plastic deformation that was associated with misfit accommodation.

K.P.Fahey, B.M.Clemens, L.A.Wills: Applied Physics Letters, 1995, 67[17], 2480-2