Addendum: Solution epitaxy of polarization-gradient ferroelectric oxide films with colossal photovoltaic current

In this article, we reported a solution epitaxy of ferroelectric oxide films, focusing on singlecrystal film of PbTiO 3 on single-crystal Nb:SrTiO 3 substrate.We would like to provide additional information to further support its epitaxy and single-crystal character by electron backscattered diffraction (EBSD) and rocking curve analysis.Figure 1a presents a typical EBSD band contrast map of PbTiO 3 film in a relatively large area, and the uniform color of the inverse pole figure (IPF) map in the Z direction (IPF Z in Fig. 1b) demonstrates that PbTiO 3 film is a single crystal.Furthermore, the fullwidth at half maxima (FWHM) of the rocking curve (Fig. 1c) scanned around the (001) diffraction peak is only 0.028°, indicating a high-quality epitaxy of PbTiO 3 film on the substrates.