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Published online by Cambridge University Press: 01 February 2011
Microstructure studies of ultra-thin BaTiO3 thin films (2–10nm thick) show nano-domains having a width as small as one unit cell. Only 180° nano-domains and 90° domain-boundaries are formed in multi-domains structures. The domain-boundaries are formed at {111} twin boundaries. Most of the domains are oriented in parallel to the film plane but out-of-plane domains are also observed. The films exhibit ferroelectric behavior characterized by a polarization hysteresis loop. A remanent polarization of 3nC/cm2, coercive field of 0.7MV/cm were measured in vertical to the film plane. Temperature-dependent polarization measurements show two peaks of the dielectric constant at about 70°C and 110° C. These peaks are attributed to two Curie temperatures associated with the out-of plane and in-plane domain's orientation, respectively. The switching response of the nano-domains is relatively fast in the range of few nano seconds. The switching time decreases with increasing the applied electric field according to a power law dependence.