Simulation of characteristics of phase transitions in ferroelectric thin films

Characteristics of phase transition in ferroelectric thin films are studied using the time dependent Ginzburg–Landau equation. Properties such as the spontaneous polarization, Curie temperature, critical thickness and susceptibility are investigated as a function of the extrapolation length, film size and the misfit strain. For free-standing PbTiO3 thin film, the supercooling and superheating temperatures can be separately determined from the spontaneous polarization changes, under temperature heating-up and cooling-down conditions, respectively. When the film grown on compressive substrate, clamped effect on film may cause film made of first-order ferroelectric material to undergo a second-order transition. In addition, we have also comprehensively analyzed the effects of film size, the extrapolation length and substrate on characteristics of phase transitions. For free standing PbTiO3 film, the different of superheating and supercooling temperature is insensitive to the film thickness and extrapolation length. The decrease of extrapolation length would not decrease the Curie temperature, but also decrease the critical thickness of the ferroelectricity. When film is thinner, the effect of the extrapolation length is larger on the change of the Curie temperature.