Intrinsic Nature of Negative Capacitance in Multidomain Hf_0.5Zr_0.5O₂‐Based Ferroelectric/Dielectric Heterostructures

Abstract

Harnessing ferroelectric negative capacitance in Hf0.5Zr0.5O2‐based thin films is promising for applications in nanoscale electronic devices with ultralow power dissipation, due to their ultimate scalability and semiconductor process compatibility. However, so far, it has been unclear if negative capacitance is an intrinsic material property of ferroelectric Hf0.5Zr0.5O2, or if it is an extrinsic effect caused by specific domain configurations and lateral domain wall motion as seen in perovskite ferroelectrics. Here, symmetric and asymmetric Hf0.5Zr0.5O2/Al2O3‐based ferroelectric/dielectric heterostructures are investigated to understand the relationship among depolarization, interfacial charge, domain formation, and negative capacitance. To achieve this, detailed electrical characterization is combined with structural data, analytical modeling, and numerical simulations. The findings suggest that negative capacitance in these ferroelectric/dielectric heterostructures is an intrinsic property of the Hf0.5Zr0.5O2 layer, which has important implications for potential applications. Furthermore, it is experimentally observed that the energy barrier for polarization switching in Hf0.5Zr0.5O2 is largely independent of the domain configuration and layer thickness, which confirms recent predictions by first principles calculations.

Double S‐Shaped Polarization – Voltage Curve and Negative Capacitance from Al2O3‐Hf0.5Zr0.5O2‐Al2O3Triple‐Layer Structure

“…First, if the minimum domain width is 50 nm, a stable NC state appears, and a single symmetric S-curve is obtained, as shown in Figure 7d. However, as confirmed in the previous study, [5] the symmetric double S-curve is obtained for the 5-nm domain width, as shown in Figure 7e. In this case, the homogeneously depolarized state is no longer a stable NC state, but the antiparallel domain configuration coincides with the lower energy state.…”

“…In the symmetric MIFIM model (with the same negative charge at the upper and lower I/F interfaces, as assumed in the previous study [ 5 ] ), different results are obtained depending on the minimum effective domain width, as shown in Figure 7d,e. First, if the minimum domain width is 50 nm, a stable NC state appears, and a single symmetric S‐curve is obtained, as shown in Figure 7d.…”

“…In this respect, the same 3D simulation of the LGD model was performed in more depth using the fitting parameters identified in the study. [ 5 ]…”

“…The original (theoretical) suggestion of the NC effect from the FE layer in the ferroelectric/dielectric (FE/DE) stacked structure was based on the phenomenological 1D Landau‐Ginzburg‐Devonshire (1D‐LGD) model. [ 1,3,5,7–13 ] In this model, the negative curvature of the Landau‐type internal energy versus polarization ( U–P ) curve of the FE material near P ≈0 was suggested to be responsible for the NC effect. However, it cannot incorporate the multidomain and domain wall (DW) effects, almost universally observed in any FE thin films.…”

Ferroelectric Hafnium Oxide Films for In‐Memory Computing Applications

“…As shown in Figure 9b, the shift of polarization hysteresis loop along the E axis is the so‐called imprint effect, which appears during the fabrication process. [ 71 ] And the imprint is the main cause of retention loss. The main reasons of imprint are the lack of oxygen vacancy formation at the electrode/ferroelectric layer interface leading the formation of a built‐in electric field, which pin the domains caused by the oxygen vacancies.…”