  Thin films of PbTiO3, a classical ferroelectric, have been grown under
tensile strain on single-crystal substrates of DyScO3. The films, of only 5nm
thickness, grow fully coherent with the substrate and show no crystallographic
twin domains, as evidenced by synchrotron x-ray diffraction. A mapping of the
reciprocal space reveals intensity modulations (satellites) due to
regularly-spaced polar domains in which the polarization appears rotated away
from the substrate normal, characterizing a low symmetry phase not observed in
the bulk material. This could have important practical implications since these
phases are known to be responsible for ultrahigh piezoelectric responses in
complex systems.
