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The dipoles cancel each other out. In addition, the

The best ratio for the VDF content is between 50% and 80% 15 and the crystalline can be increased through annealing the material at a temperature above the Curie point and lower the melting point 15. Another for this work important ferroelectric properties are the dielectric nonlinearities ? which will be modeled after 13 as complex because of the conductivity of the amorphous parts and nonlinearity at the crystal parts. The amorphous parts are chains in between the parallel chains, but having no order 13. This leads to that the dipoles of the chain are distributed in a way that the force caused by the dipoles cancel each other out. In addition, the amorphous part makes no contribution to the remnant polarization still the amorphous parts are needed in small amounts. Furthermore, the samples must be thin films with a thickness not stronger 1?m. The reason is simply the needed electric fields are too high to work with bulk material.The growth of superlattices is a promising approach to create artificial materials with unique properties. Like described by Koehler 6 this is done by the combination of two or more materials with diffeerent electronic properties and lattice parameters in an alternating layer system while each layer has a thickness of several nanometers.As stated by Lichtensteiger et al. 7 it has been focused on perovskites during the past years due to their well known ferroelectric properties. Material combinations that has been researched on are for example BaTiO3/SrTiO3, KNbO3/KTaO3, PbTiO3/SrTiO3, PbTiO3/PbZrO3 and a so called tricolor superlattice of SrTiO3/BaTiO3/CaTiO3. The layers of the materials are grown by epitaxial deposition techniques such as pulsed laser deposition, sputtering or oxide molecular beam epitaxy.The created unique properties are varying dramatically between the different material combinations. In the case of BaCuO2/SrCuO2 superconductivity can be seen although none of the two materials is superconducting 8. The same can be observed in SrZrO3/SrTiO3 superlattices with respect to ferroelectricity 9. The above mentioned tricolor structure of SrTiO3/BaTiO3/CaTiO3 breaks the inversion symmetry which allows ferroelectricity 10. By varying the composition of the tricolor superlattice the ferroelectric properties are tunable. Superlattices consisting of more than one ferroelectric, for example PbTiO3/BaTiO3, are considered to be useful to study polarisation switching processes and domain dynamics 11, especially when the polarisation of the used ferroelectrics exhibits similar magnitudes, while the polarisation switching behaves differently. LaAlO3/SrTiO3 superlattices possess charge discontinuities at the LaO/TiO2. Theoretical Model of Electrostatic Coupling and Interface Intermixing interface, which form a conduction channel between the single layers consisting of nonferroelectric insulators. Combining a ferroelectric insulator and another insulator resulting in a similar conduction channel could lead to the tunability of ferroelectric coupling between superlattice layers 12.It becomes obvious that there are multiple ways to combine a wide range of materials in superlattices with a variety of different effects that can be studied. Moreover, they have an immense potential of being used for innovative applications. In the next passages the focus lies on superlattices where ferroelectric and paraelectric materials are combined since these multilayer systems seem to be realizable most easily with the well studied polymer PVDF and its copolymer P(VDF-TrFE).As a matter of fact, the behaviour of materials in superlattices differs from that in bulk material. The neighboring layers in influence each other in an electrical and a mechanical way. Additionally, intermixed layers can form at the interfaces between the layers. The formation of these intermixed layers can hardly be controlled and their properties are different from the adjacent layers, which may affect the behavior of superlattices.


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