Modeling the roles of oxygen vacancies in thin film ferroelectric memory

The role of oxygen vacancies in thin ferroelectric film is modeled and the corresponding ferroelectric properties are numerically simulated using Ising Model. The octahedral cage of a perovskite cell is distorted in the presence of oxygen vacancy. Thus the originally symmetric potential for the titanium ion is now asymmetric due to the distortion. In the Monte Carlo simulation, the Hamiltonian of the dipole system is modified by this distorted potential. The latter also affects the probability of the flipping a dipole as well as the coupling between the neighboring dipoles. These oxygen vacancies are modeled to be randomly distributed at the electrode/film interfaces. Experimental results in frequency response, amplitude dependence, fatigue and distorted hysteresis loops are numerically reproduced