We have observed nonorthogonal twinning in thin him oxide perovskites.
This twinning geometry is equivalent to a 60 degrees rotation of the
twinned crystallites about the [111] direction in an [001] oriented fi
lm. This twinning is not detectable by the standard x-ray tests for fi
lm quality (a radial theta-2 theta scan and a phi scan at a chi of 45
degrees). In this study we observe this twinning in films of PbZrxTi1-
xO3, BaTiO3, and SrRuO3 grown by sputtering and MOCVD on MgO and SrTiO
3. These twins are observed in films deposited on a substrate with whi
ch there is a large lattice mismatch and in films that are deposited i
n an oxygen deficient environment. We propose that these twins result
from plastic deformation associated with misfit accommodation and disc
uss the twin geometry and the nature of the twin interface. (C) 1995 A
merican Institute of Physics.