Thickness dependence of ferroelectric domains in thin crystalline films

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Abstract
The thickness dependence of ferroelectric domains in thin free-standing BaTiO3 crystalline films has been studied by transmission electron microscopy. It is found that the widths of ferroelectric domains decrease as the film thickness decreases. This phenomenon may indicate that the ferroelectric properties of thin films are weakened due to surface relaxation effects, including lattice relaxation and a change of spontaneous polarization and charge compensation. The weakening of ferroelectric domains is suggested as a transition state from ferroelectric to paraelectric phase of the BaTiO3 thin film. The thickness of the surface relaxation layer of totally nonferroelectric film is on the order of 10 nm.