Engineering 180° ferroelectric domains in epitaxial PbTiO₃ thin films by varying the thickness of the underlying (La,Sr)MnO₃ layer

Epitaxial ferroelectric thin films of PbTiO₃ (PTO) grown on top of nominally La_0.7Sr_0.3MnO₃ (LSMO) submicron hillocks on Nb-doped SrTiO₃ (100) substrate were investigated by means of scanning transmission electron microscopy. 180° ferroelectric domains were observed in the c-axis oriented PTO films. The formation and configuration of ferroelectric domains and domain walls were found to exhibit strong correlation with the thickness of the underlying LSMO hillocks. The domain walls start at the locations of the hillocks where the LSMO layer has a thickness of about 3nm. Our results demonstrate that controlling the thickness variation (shape) of the LSMO hillocks can manipulate the position and density of the ferroelectric domain walls, which are considered to be the active elements for future nanoelectronics.