Preferred alignment of twin boundaries in YBa2Cu3Ox thin films and YBa2Cu3Ox/PrBa2Cu3Ox superlattices on SrTiO3

Abstract
The structure of YBa2Cu3Ox thin films and YBa2Cu3Ox/PrBa2Cu3Ox superlattice films grown on (00L) SrTiO3 substrates has been studied using x‐ray diffraction and transmission electron microscopy. The films consist of four symmetry‐equivalent domains related by mutually perpendicular (hh0) and (hh̄0) twin boundaries. One twin orientation is often highly favored over the other. We have correlated this in‐plane symmetry breaking with small miscuts of the substrate surface towards the [HH0] direction and propose that interfacial steps act as nucleation sites for twins. Thus, by controlling the surface normal, a technique is described for producing films containing aligned twin boundaries.