Ferroelectric Domains Evolotion And Optical Properties In BiFeO₃ Thin Films

Ferroelectric has many excellent properties, such as dielectric, ferroelectric, piezoelectricity, pyroelectric, photoelectric effect, acousto-optic effect and so on, It can be widely used in storage, sensors, optical and acoustic devices. Therefore, It is always the hot topic of research. BiFeO₃ is one of the most promising materials in ferroelectrics, and the domain structure of BiFeO₃ thin films will have a great influence on its properties, so it is very important to study the domain structure of ferroelectrics.BiFeO₃ thin film was prepared by pulsed laser deposition. The mophology, ferroelectric domains and photoelectric effect were characterized by a commercial atomic force microscope （AFM） with a piezoelectric force microscope （PFM） mode. This paper mainly focus on:（1） studied the domain evolution under external electrical and mechanical force, （2） measured the intrinsic conductive and photovoltaic effects at different temperature on the polarizaed area.For the domain evolution under electrical:when realise 180° polarization switching, the aligned domains may undergo 71°/109°/180° or 109°/71°/0° reversed paths. The mechanical switching of polarization paths are similar to the process of the electric field, At the same time, because of the intermediate state, which makes inversion barrier decrease, this explanation for the microscopic mechanism of fatigue has great significance.Conductive atomic force microscope（C-AFM） was used to characterize its conductive of its polarized domain, and we measured the photovoltaic effect of BiFeO₃ thin films. It was interesting to find that the Isc increases from 180 nA to 404 nA as the temperature increasing from 20℃ to 130℃.In summary, the swtching evolution of polarization have many intermediate states under mechanical and electrical control. Most importantly, we studied the photovoltaic behavior at different temperatures. These results were important for the understanding of domain evolution in ferroelectric films, the design of high performance storage and the application of photovoltaic devices at different temperature and polarization states.