| Ferroelectric thin film has become a popular research field because of its high storage density, fast reading and writing speed, low energy consumption and wide application range.In this field, the Bi4Ti3O12（BTO） ferroelectric thin films and BiFeO3（BFO） multiferroic films attract more attention due to lead free and better performance. In this paper, we prepared Bi3.25La0.75Ti3O12（BLTO） and Bi3.96Sb0.04Ti3O12（BSTO） ferroelectric thin films,Bi1.7Sb0.3Ti2O7/ BSTO composite films using a sol-gel technique on Pt / Ti / SiO2 / Si substrates. We also prepared Bi1-xNdxFeO3, BiFe1-y CoyO3 and Bi0.85Nd0.15Fe0.85Co0.15O3（BNFCO） multiferroic thin films using the same method. The structure and properties of these films were studied in detail.Ferroelectric devices has important value in aerospace because of the anti radiation characteristics. But the space environment is complex where exist various rays and they will inevitably cause effect on ferroelectric devices. In order to study the effects of radiation on ferroelectric thin films, we use BLTO ferroelectric thin film as the research object to carry out different dose of 60Co-γ ray irradiation. According to the performance before and after irradiation we found that the compactness and uniformity of the film surface were decreased after irradiation, the grain becomes irregular and smaller; thin film ferroelectric properties reduced, remanent polarization 2Pr and coercive field 2Ec were both decreased with the increasing of radiation dose, under the test electric field of 600kV/cm, 2Pr decreased from51.1μC/cm2 to 43.5μC/cm2, 37.4μC/cm2 and 23.7μC/cm2, 2Ec were also decreased from 178.3kV/cm to 165.1 kV/cm, 163.5 kV/cm, 149.2 kV/cm after irradiation; C-V curve became obvious asymmetry, and with the radiation dose increased the increase of asymmetry rate;Leakage phenomenon has been alleviated after irradiation, as the radiation dose increased leakage current density decrease; The BLTO film showed good anti fatigue after irradiation,and even after 1010 switch polarization cycle, there is little change in the remnant polarization.Bi4-xSbxTi3O12 ferroelectric thin films with different Sb3+ contents（0.03, 0.04, 0.05, 0.06,0.07） were prepared on Pt / Ti / SiO+2 / Si substrates. Through the comparative study of Bi1-xSbxTi3O12 and pure BTO ferroelectric thin films, it can be seen that when x=0.04, the film Bi3.96Sb0.04Ti3O12（BSTO） has better performance: the film shows good ferroelectric properties,in the applied voltage 35 V, the remanent polarization up to 87.6μC/cm2; At the same time the film BSTO shows good anti fatigue performance and low leakage current density.Doped Bi2Ti2O7 has stable phase, low leakage current and high dielectric constant excellent characteristics, is an ideal material for buffer layer. In this paper the Bi2-x SbxTi2O7 thin films with different Sb3+ content were prepared, and the characteristics of XRD, SEM,C-V curve and leakage current density of the thin films were analyzed. The results show that when x=0.3 the film Bi1.7Sb0.3Ti2O7 performance were better than other films. The Bi1.7Sb0.3Ti2O7 as a buffer layer fabricated Bi1.7Sb0.3Ti2O7/ BSTO composite films. Based on the ferroelectricity, fatigue resistance and leakage current characteristics were measured and characterized. It can be found that the saturation and the rectangle of the P-V loop are relatively good, indicating that the ferroelectric properties of the films have significantly improved; In the case of the remanent polarization is not changed, the coercive field is decreased; Leakage current density decreased by about two orders of magnitude; C-V curve occurred significantly improved.Bi1-xNdxFeO3, BiFe1-yCoyO3 and BNFCO series of multiferroic thin film were prepared on Pt / Ti / SiO2 / Si substrates, in which x and y values were 0.05, 0.10, 0.15 and 0.20,respectively. XRD, ferroelectric properties and leakage current density tests were performed on all thin films. The results show that both A site and B site doping did not change the crystal structure of BFO; In a certain Nd3+ doped range, the remnant polarization 2Pr of multiferroic thin film Bi1-xNdxFeO3 increased from 7.25μc/cm2 to 14.03μc/cm2, 26.21μc/cm2 and19.13μc/cm2 with the increase of Nd3+content. When the content of Nd3+is 0.15, 2Pr reaches a maximum value 26.21μc/cm2; Corresponding to different Co2+ content, the remanent polarization 2Pr of Bi Fe1-yCoyO3 multiferroic thin film were 9.1μc/cm2, 19.1μc/cm2,33.6μc/cm2 and 22.1μc/cm2. When the Co2+content is 0.15, the 2Pr value reaches the maximum value of 33.6μc/cm2; Nd3+ and Co2+ Co doped at both A and B sites, the remnant polarization 2Pr of BNFCO thin film reaches 49.7μc/cm2; No matter which way the films doped, the leakage current density compared to BFO, decreased by 4 to 5 orders of magnitude. |
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