Electrical investigation of thin ferroelectric films and nano structures

Today widely used ferroelectrics are investigated since the discovery of the ferroelectricity in Rochelle salt in 1920. The main property of ferroelectrics is appearance of spontaneous polarization at certain temperature, which direction can be changed by an external electric field. Ferroelectrics and related materials, such as ferroelectric relaxors, are widely investigated class of materials due to both scientific and engineering point of view. Real ferroelectric materials have internal electric fields due to finite size, charged defects, and inhomogeneities in the material. This is even more pronounced in thin films. These inevitable fields are often considered a hurdle, typically causing degradation of properties. Several recent studies showed strongly enhanced properties (piezoelectric, dielectric, photovoltaic) originating from internal fields, hinting that internal fields could be beneficial if properly addressed. This triggered to propose the present thesis, in which all attention was dedicated for understanding of internal fields in ferroelectrics. So, in this work, electrical investigation of thin ferroic films and nanostructures are presented. Here, heterostructure of Ba0.7Sr0.3TiO3/La0.8Sr0.2MnO3//SrTiO3 and Ba0.7Sr0.3TiO3/SrRuO3//SrTiO3 where investigated and also, 0.71Pb(Mg1/3Nb2/3)O3 – 0.29PbTiO3 single crystals and 0.67Pb(Mg1/3Nb2/3)O3 – 0.33PbTiO3 epitaxial thin films were analysed in a broad temperature and frequency ranges