铁电薄膜平均极化性质的研究

Study on the Average Polarization Property of Ferroelectric Film

应用Ginzburg-Landau-Devonshire(G-L-D)理论,研究由两种铁电材料组成的铁电双层膜系统的极化性质.通过引入的两个参量:参量α(描述铁电双层膜系统中两种铁电体的物理性能差异)和参量γ(描述铁电双层膜系统两种铁电体相变温度的差异),研究了不同的表面过渡层和双层膜系统厚度的条件下,铁电双层膜系统平均极化随这两个参量的变化情况.研究表明:参量α增大时,铁电双层膜系统的平均极化随之增大.当α取固定值时,平均极化随双层膜厚度L、表面自由能随位置变化的速度λ增大而增大;随着表面过渡层厚度Ls的增大而减小.参量γ增大时,铁电双层膜系统的平均极化减小.当参量γ取固定值时,平均极化随着表面过渡层厚度Ls的增大而减小;随着参量α、双层膜厚度L、表面自由能随位置变化的速度λ的增大而增大.

The polarization property of the ferroelectric bilayer film consisting of two different ferroelectric materials is studied by Ginzburg-Landau-Devonshire theory. Through two parameters introduced, that is, parameter a （ which describes the differences of physical property between two ferroelectrics in the ferroelectric bilayer film ）;parameter γ, （which describes the differences of ferroelectric phase transition temperature between two ferroelectrics in the ferroelectric bilayer film）. Accordingly, the variation of the average polariza- tion of ferroelectric bilayer film with these two parameters under different surfieial transition layer and bilayer film thickness is studied. The results indicate that the average polarization of ferroelectrie bilayer film will increase as the parameter α enhances. With α being a fixed value the average polarization will increase as the thickness L of the bilayer and the rate γ enhance, at which the surface free energy varies with position ; and the average polarization will decrease with the thickness Ls of surficial transition layer increasing. The average polarization of ferroelectric bilayer film will decrease as the parameter γenhances. With γbeing a fixed value, the average polarization will decrease with the thickness Ls of the surficial transition layer increasing; and it will increase as the parameter α, the thickness L of bilayer and the rate γ at which the surface free energy varies with position increase.