Theoretical Analysis For Ferroelectric Thin Films Hysteresis Loop

Ferroelectric thin films possess the excellent properties such as ferroelectric, piezoelectric, pyroelectric, electro-optic, acousto-optic and nonlinear optical and so on, which aroused widely concern of scholars. With the continuous improvement of the thin films technology, researchers have develop abundant ferroelectric thin film Integrated (example:capacitors, non-volatile ferroelectric random access memory, etc.), which have expansive prospects. Due to the birth and development of integrated electrical iron, people pay more attention to the design and simulation of integrated circuit which consists of ferroelectric thin films and semiconductor. Hysteresis loop is an important characteristic of ferroelectrics, and a lot of research has been done to explore the mathematical model, however, up to now there is no a brief and physical meaning model.The main work of this paper is to summarize and analyze the classic ferroelectric hysteresis loop experimental phenomena and various explanations, combine the ferroelectric polarization reversal mechanism, and establish a reasonable ferroelectric hysteresis loop model.There are lots of factors that affect the ferroelectric hysteresis loop, such as doping, annealing temperature, annealing atmosphere, reverse voltage and electrodes, etc. Therefore, the ferroelectric hysteresis loop obtain from different experiments are different, some saturated, some unsaturated, some symmetry and some non-symmetry. The previous models either lack the necessary physical basis, or do not have general applicability. In this paper the unit cell is equivalent to dipole based on macroscopic feature (hysteresis loop) and microstructure of ferroelectric. After analyzing the dipole polarization reversal mechanism in an applied electric field, a new ferroelectric thin films'hysteresis loop model is established which make use of the basic principles of statistical physics. In the modeling process, the method extract the dipole shift probability function in the applied electric field from previous experimental results, and the function is processed by Fourier transform to obtain the correct fitting parameters.The paper uses the model established to simulate the hysteresis loop in different doping, annealing condition, reverse voltage and electrode, and compare the experiment result with the existing ones. It is easy to find that the simulation result of model in this paper essentially corresponds with the experiment data. The simulation result shows that the model not only applies to the saturation polarization and non-saturated polarization, but also applies to symmetrical and asymmetric hysteresis loop, which prove that the model has excellent general applicability. In addition, owing to the fewer parameters, the model in this paper is briefer and easier than existing ones.