Heteroepitaxial PbTi O3 film on an Nb-doped (001) cubic SrTi O3 substrate was fabricated by hydrothermal epitaxy at 200 °C. Piezoresponse force microscopy and x-ray Θ rocking curves confirmed that the film showed a caca multi-domain structure even though it did not undergo a cubic paraelectric (PE) to tetragonal ferroelectric (FE) phase transition. After heat treatment of this film at 600 °C, we observed the  surface band within the a -domain, which was formed through the PE to FE phase transition. We also found that a  surface band existed along the (1 1- 1) plane within the a -domain. We predicted that the  surface band would be monoclinic phase due to the interaction of two different variants of a -domains in the presence of a c -domain in the heteroepitaxial PbTi O3 film.