Limitations to Electrical Probing of Spontaneous Polarization in Ferroelectric-Dielectric Heterostructures

Abstract

An accurate estimate of the ferroelectric polarization in ferroelectric-dielectric stacks is important from a materials science perspective, and it is also crucial for the development of ferroelectric based electron devices. This paper revisits the theory and application of the PUND technique in Metal-Ferroelectric-Dielectric-Metal (MFDM) structures by using analytical derivations and numerical simulations. In an MFDM structure the results of the PUND technique may largely differ from the polarization actually switched in the stack, which in turn is different from the remnant polarization of the underlying ferroelectric. The main hindrances that prevent PUND measurements from providing a good estimate of the polarization switching in MFDM stacks are thus discussed. The inspection of the involved physical quantities, not always accessible in experiments, provides a useful insight about the main sources of the errors in the PUND technique, and clarifies the delicate interplay between the depolarization field and the charge injection and trapping in MFDM stacks with a thin dielectric layer.

Interplay Between Charge Trapping and Polarization Switching in BEOL-Compatible Bilayer Ferroelectric Tunnel Junctions

“…The plotted curves are obtained by integrating the difference in P-U and N-D currents, which should provide an estimate of the switched polarization without influence of leakage and displacement currents. It should be pointed out that this does not necessarily correspond entirely to the polarization switching current, as highlighted recently [26]. From Figure 2(b) it is clear, nonetheless, that the switched charge is larger for CMP devices.…”

Analytical Procedure for the Extraction of Material Parameters in Antiferroelectric ZrO2

“…The timescale of the voltage pulses in these experiments (now comparable to the t ρ ), and the relatively thick DE were on purposely chosen to minimize the role of charge injection and trapping [17]. Therefore, our simulations neglect trapping, which has been shown to be instead important in quasi-static measurements for FE-oxide stacks having a thin DE layer [25], [37]. Fig.…”

“…In Section IV, we will illustrate several comparisons between simulations and experiments aimed at a validation of the extraction procedure for the anisotropy constants of ZrO 2 . All simulations were carried out by using the solver for the multidomain LGD equations that has been already discussed in [19], [24], and [25]. In this section, we recall only a few aspects of the simulation framework, which are relevant for the cases at study in this article.…”

“…For an AFE or an FE material consisting of n D domains, as shown in Fig. 2, the dynamics of the polarization P i in each domain is described by the following equations [19], [24], [25]:…”

Ferroelectric based FETs and synaptic devices for highly energy efficient computational technologies

“…Fig. 5(a), for example, it has been argued that, if charge injection in the dielectric stack is not accounted for, simulation results predict P-V hysteretic curves much narrower and more tilted than their experimental counterpart [38], [39]. Hence, in these devices, the interplay between the charge trapping, the stabilization and the compensation of the ferroelectric polarization becomes quite delicate [40].…”