Study on the phase transition dynamics of HfO₂-based ferroelectric films under ultrafast electric pulse

Abstract

Wake-up effect and fatigue in HfO 2 -based ferroelectric films are closely related to the phase transition dynamics of the film subjected to ultrafast electric pulses. Here, we establish a multiphase coexistence phase field dynamics model for HfO 2 -based ferroelectric films in the ultrafast time scale and study the effects of the amplitude, width and frequency of the electric pulse on the phase transition dynamics. Based on the simulation results, we obtain the analytical equation of the volume fraction of switched c-domains under low fields as a function of pulse duration. And we found that monoclinic phase can transform into ferroelectric c-domains under high amplitude electric field (E 2.8 MV cm −1 ). The electric pulse duration affects the film's retention properties. When the duration of the electric pulse is less than 1.2 ns or longer than 1.8 ns, the ferroelectric c-domains will respectively invert into other phases or increase cumulatively after removing the electric field. The frequency of cyclic pulse is related to the degree of wake up effect. The lower the pulse frequency is, the more obvious the 'wake up' effect is.

Electric-field-induced crystallization of Hf0.5Zr0.5O2 thin film based on phase-field modeling

“…It should be noted that the higher-order terms of Landau energy exclude the coupling between various variants of the ferroelectric phase and amorphous phase. This is because not considering it will not affect the main result [25].…”

Synergistic effect of Si concentration and distribution on ferroelectric properties optimization of Si:HfO2 ferroelectric thin films

“…In this paper, the multi-phase coexistence phase field model of hafnium-based ferroelectric films established in our previous research is extended to include the Si dopant [17,18].…”

“…where A 1 , A 2(o) , A 2(m) , A 3, and A 4 are Landau coefficients that depend on the concentration of Si, According to the method used in [18,19,21], we preliminarily constructed the basic functional relationship between Landau energy coefficient and doping concentration. Then, based on the experimental data of [8], the specific form of the Landau energy coefficient equation with Si concentration as the independent variable is determined, i.e.…”

“…For convenience, coefficients and variables in the above equations are nondimensionalized. The basic physical quantities for dimensionless process include the spontaneous polarization at the room temperature P = 0.45 µC cm −2 and length ∆l = 1 × 10 −9 m, and the dimensionless method can be found in [18]. The system size used in the simulations is 10∆l × 10∆l.…”

“…Since the film is constrained by two electrodes, the mechanical boundary conditions on the top and bottom interface of the film are set as µ 1 = µ 2 = 0. Furthermore, the electric potentials of the top and bottom interface of the film are taken as V 1 = V 2 = 0 [18,29].…”