Built-in voltage in thin ferroelectric PbTiO3 films: the effect of electrostatic boundary conditions

Abstract

We have studied the built-in voltage in heterostructures composed of ferroelectric PbTiO _3 and dielectric spacers of SrTiO _3 , grown on SrTiO _3 substrates with SrRuO _3 bottom electrodes. We used piezoresponse force microscopy to determine the domain structure of the samples and perform local switching experiments. By increasing the thickness of the SrTiO _3 spacer layers, we were able to tune the polarization configuration in the PbTiO _3 films by gradually going from a monodomain configuration to a polydomain one. The built-in voltage was found to be linked to the choice of electrodes and to the thickness of the spacer layer. The stability of artificially poled regions was also affected, with a faster back-switching for the samples with the thicker SrTiO _3 spacers. We have additionally compared samples with and without a top SrRuO _3 electrode, showing that a top electrode layer results in a stronger built-in voltage, responsible for a preferential monodomain configuration and a very fast back-switching of artificially poled regions.

Keywords

• ferroelectricity
• ultrathin epitaxial films
• interfaces
• piezo-force microscopy
• polarization
• electrostatic boundary conditions