Computer Simulation Of The Fatigue Characteristics Of Ferroelectric Thin Films

Since the idea about ferroelectric memory were put forward in 1950s, extensive investigations have been carried out on this device. Ferroelectric thin film, which is characterized by its large remnant polarization, rapid switching and small leakage current etc., has been regarded as the best material for the facture of ferroelectric memory devices. However, this material is notorious of its fatigue character. That is, the effective polarization of ferroelectric thin film capacitance decreases greatly with the repetition of polarization reverse, then the decrease of effective polarization will depress the switching currents. Thus, the units of ferroelectric memory will output ambiguous '0' and '1' . The failure of reading and writing will lead to the lose of information at last. Since the fatigue character has greatly prevented the ferroelectric thin film from application in memory devices, it becomes more and more important to study the origination of this fatigue character and to resolve this problem.Monte-Carlo method has been widely used to simulate the physical process and this simulation can always get satisfactory results. In this thesis, the ferroelectric fatigue process was simulated using Monte-Carlo method by computer based on DLA model combined with Ising model. The results about the simulation of electric hysteresis loops, switching current curves and the formation process of ferroelectric domains under different defect concentrations, temperatures, electrical fields and frequencies were obtained. It was found that the reversal of polarization in ferroelectric thin film can be affected greatly by defects, temperature, and electrical field.The defects can facilitate the formation of ferroelectric domain core...