Extensive studies have been done on local ferroelectric properties of Pb(Zr,Ti)O3 (PZT) thin films with a scanning force microscope. It is interesting to look into whether the relaxation behavior of charges and polarization in PZT systems can be generalized to other ferroelectric materials. In this study, we have explored two representative materials Bi3.25La0.75Ti3O12(BLT) and PbMg1/3Nb2/3O3-PbTiO3(PMN-PT). The former is well-known as fatigue-free and the latter is relaxor-type and known as a material with a large piezoelectric coefficient. Fatigue-free ferroelectric BLT thin films on Pt/TiOx/SiO2/Si(100) and SrRuO3/SrTiO3(100)substrate were fabricated by multiple coating of solution and crystallization process. The control of local ferroelectric polarization and crystalline orientation are important issues in fabrication of nonvolatile storage devices using the BLT thin films. Local electrical properties of the BLT films are measured with a scanning force microscope. Topography and electro-static microscopic imaging have been performed at room temperature where the films are in the ferroelectric state. From the measurements, various relaxation and poling phenomena are observed and models to explain the distribution of surface charges. Relaxor ferroelectric PMN-PT thin films were grown by a sol-gel method. Poling and imaging were performed in a number of regions on the films surface sized with subsequent statistical analysis of the obtained data. Surface charges and poling behavior appear to have a relation with relaxor behavior of the materials, which is defined as frequency-dependent phase transition in ferroelectric materials. Polarization-electric field hysteresis loops are observed and dependent on the sweeping frequency due to relaxation dominated properties of the films.
[REF] T. Y. Kim, J. H. Lee, Y. J. Oh, M. R. Choi, and W. Jo, Appl. Phys. Lett. 90, 082901 (2007). |