Investigation On Electrical Properties Of Sr Doped BiFeO₃-based Films

With the increase of sensors, resonators, drive, non-volatile memory, the ultrasonic transducers and other ferroelectric thin film electronic component demand, the preparation of low-cost, high-life, multi-functional integrated ferroelectric thin film materials is highly attention by researchers. In recent years, BiFeO3 (BFO), as an ideal environment-friendly lead-free multiferro-materials, because of its excellent ferroelectric, piezoelectric and ferromagnetic properties, is expected to replace Pb(Zr,Ti)O3(PZT) in the future in micro-electromechanical systems, which will be widely used.Currently, many factors still restrict the application of BFO thin film. On the one hand, the preparation process of BFO film is still not mature enough, BFO thin film prepared a performance of instability and the performance is not good; on the other hand, during the preparation of BFO thin film, since the atmosphere and other reasons, easy fluctuations in Fe valence (mainly trivalent iron is reduced to ferrous iron, valence decrease) occurs, in order to achieve price equilibrium would aerobic vacancy generation, which will allow leakage problem film samples prepared intensifies, thereby affecting the film other aspects of performance prepared, such as ferroelectric properties. Therefore, researchers become research focus on further optimization of the preparation process, doping, and build a multi-layer structure by means of improved performance BFO film.In this paper, using the sol-gel method, layers by layer of the annealing process, a series BFO-based film with different parameters have been prepared. Through a series of studies, we have draw several conclusions.(1) The amount of excess Bi have a greater impact on the structure and properties of BFO thin film samples. Explore the best percentage of excess Bi, when Bi excess of 10mol%, the presence of film samples prepared in morphotropic phase boundary(PPB), near the MPB, the phase structure of the film has a greater activity, which will help to improve the properties of the film samples. when the applied electric field of 600 kV/cm, the leakage current density is 7.8×10-7A/cm2, when the applied frequency of 105 Hz, the dielectric constant is 208, the dielectric loss film is 0.042.(2) Through systematic research on the BSFMOX thin films, investigate the best dosage of Sr is 2mol%, the best annealing temperature is 525℃, BSFMOx=2moi% prepared residual polarization strength is 90.129 μ C/cm2 with a coercive field of 282.37kV/cm at measured electric field value of 800kV/cm, the leakage current density is 4.5×10-7A/cm2 at applied electric field of 350kV/cm,the test frequency is 105Hz, the dielectric constant and the dielectric loss is 232,0.190, respectively.(3) Using Sr2Bi4Ti5O18 (SBTO) films and BSFMO films to construct two-layer structure, reduces the leakage current density of BSFMO film sample. Also found that organizations build a double, making a rectangle of the film samples prepared and residual polarization value decreases.As innovation, in the aspect of analysis mechanism, That the freedom of movement oxygen vacancy (Vo2-) or substituted bismuth strontium ion (SrBi3+2+)’rather than (SrBi3+2+)-(Vo2-) is the carrier of the transmission leakage contributes to the film. The leakage current and multiferroic properties of BiFeO3-based films are significantly improved by Sr doping and forming the double-layered structure, open a new idea of the preparation of thinner films, which can pave the way for the development of future microelectronic devices.