Nanoferroelectric domains in ultrathin BaTiO3 films

The microstructure and electrical properties of ultrathin ${\mathrm{BaTiO}}_3$ films (2–7 nm thick) have been studied. Multidomain structures having 180° domains and 90° domain boundaries were observed by high resolution transmission electron microscopy. The domains, which have a width as small as one unit cell, are mostly oriented in parallel to the film plane. The film exhibits ferroelectric behavior characterized by polarization hysteresis loops and Curie temperature. The leakage current, switching time, and fatigue characteristics of the films are also reported.