The research status and device potential of ferroelectric thin films

Some of the problems of fabricating thin films of mixed oxide ferroelectrics possessing electrical properties comparable to those of the bulk material are discussed. It is shown that crystallographic disorder and non-stoichiometry can lead to anomalous behavior in dielectric properties such as permittivity and loss. If care is taken to produce homogeneous and well-crystallized structures, polarization reversal effects closely similar to those characteristic of the bulk ferroelectric can be obtained. In particular, the crystalline anisotropy of polarization and optical properties in epitaxial bismuth titanate films follows closely that observed in single crystals. Moreover, bulk-type electro-optic switching behavior is observed in these structures, offering good prospects of using them as display media. The optimization of ferroelectric properties for capacitors, memories and displays is discussed and some of the new device potentialities for ferroelectric films in general are evaluated.