A simulation-based study of variability of remnant polarization $\left (P_r \right)$ in a multi-granular 3-D ultra-thin ferroelectric (FE) capacitor is presented in this paper. The Poisson Voronoi Tessellation Diagram (PVD) is used for the nucleation of grains in the FE region, which corresponds to the physical growth mechanism. The PVD algorithm implemented in MATLAB is coupled with TCAD simulations, to trace the ferroelectric hysteresis loop. It is found that the grains which have linear profile of $P_r$ show larger variability in the FE hysteresis loop, compared to the grains, which follow the Gaussian distribution of $P_r$. Additionally, the impact of dielectric content in the FE grains is analyzed. It is seen that the dielectric grains cause very large amount of variability in the FE hysteresis loop. An increase in the dielectric grains also leads to a loss in the retentivity of the hysteresis loop.
Transient negative differential capacitance (NC), the dynamic reversal of transient capacitance in an electrical circuit is of highly technological and scientific interest since it probes the foundation of ferroelectricity. In this letter, we study a resistor-ferroelectric capacitor (R-FeC) network through a series of coupled equations based on Kirchhoff's law, Electrostatics, and Landau theory. We show that transient NC in a R-FeC circuit originates from the mismatch between rate of free charge change on the metal plate and that of bound charge change in a ferroelectric (FE) capacitor during …
This paper investigates the thermodynamic driving force of transient negative capacitance (NC) in the series circuit of the resistor and ferroelectric capacitor (R-FEC). We find that the widely used Landau-Khalatnikov (L-K) theory, that is, the minimum of the Gibbs free energy, is inapplicable to explain the transient NC. The thermodynamic driving force of the transient NC phenomenon is the minimum of the difference between the elastic Gibbs free energy and the electric polarization work. The appearance of the transient NC phenomenon is not due to the widely accepted view that the ferroelectri…
In this study, we propose a measurement technique for evaluating ferroelectric polarization characteristics in ferroelectric field-effect transistors (FeFETs). Different from standard metal/ferroelectric/metal capacitors, the depletion and inversion phenomena in semiconductor substrates have to be carefully taken into account when evaluating the ferroelectric properties using fast voltage sweep as input. The non-equilibrium deep depletion is found to be the limiting factor for the accurate evaluation of ferroelectric properties in metal/ferroelectric/semiconductor capacitors. By connecting the…
In this letter, the transient behavior of a ferroelectric (FE) metal-oxide-semiconductor (MOS) capacitor is theoretically investigated with a series resistor. It is shown that compared to a conventional high-k dielectric MOS capacitor, a significant inversion charge-boost can be achieved by a FE MOS capacitor due to a steep transient subthreshold swing (SS) driven by the free charge-polarization mismatch. It is also shown that the observation of steep transient SS significantly depends on the viscosity coefficient under Landau's mean field theory, in general representing the average FE time re…
The negative capacitance (NC) stabilization of a ferroelectric (FE) material can potentially provide an alternative way to further reduce the power consumption in ultra-scaled devices and thus has been of great interest in technology and science in the past decade. In this article, we present a physical picture for a better understanding of the hysteresis-free charge boost effect observed experimentally in metal-ferroelectric-insulator-metal (MFIM) capacitors. By introducing the dielectric (DE) leakage and interfacial trapped charges, our simulations of the hysteresis loops are in a strong agr…
Half of the energy is always lost when charging a capacitor. Even in the limit of vanishing resistance, half of the charging energy is still lost--to radiation instead of heat. While this fraction can technically be reduced by charging adiabatically, it otherwise places a fundamental limit on the charging efficiency of a capacitor. Here we show that this 1/2 limit can be broken by coupling a ferroelectric to the capacitor dielectric. Maxwell's equations are solved for the coupled system to analyze energy flow from the perspective of Poynting's theorem and show that (1) total energy dissipation…
Epitaxial ferroelectric Hf0.5Zr0.5O2 films have been successfully integrated in a capacitor heterostructure on Si(001). The orthorhombic Hf0.5Zr0.5O2 phase, [111] out-of-plane oriented, is stabilized in the films. The films present high remnant polarization Pr close to 20 μC/cm2, rivaling with equivalent epitaxial films on single crystalline oxide substrates. Retention time is longer than 10 years for writing field of around 5 MV/cm, and the capacitors show endurance up to 1E9 cycles for writing voltage of around 4 MV/cm. It is found that the formation of the orthorhombic ferroelectric phase d…
Designing high endurance Hf0.5Zr0.5O2 capacitors through engineered recovery from fatigue for non-volatile ferroelectric memory and neuromorphic hardware
Tunable Defect Engineering of Mo/TiON Electrode in Angstrom-Laminated HfO$_2$/ZrO$_2$ Ferroelectric Capacitors towards Long Endurance and High Temperature Retention
Since the recent discoveries, ferroelectric nematics became of upmost interest due to their outstanding ferroelectric properties. In this work, we prepared a series of polar molecules revealing a ferroelectric nematic phase (NF) with a very high dielectric constant (>104). A new motif, which differs from previously reported molecular structures, was optimized to support the NF phase. For all homologues the NF phase was observed directly on the cooling from the isotropic phase and ferroelectric behaviour was investigated by dielectric spectroscopy, second harmonic generation, polarization curre…
In this paper, the multi-domain nature of ferroelectric (FE) polarization switching dynamics in a metal-ferroelectric-metal (MFM) capacitor is explored through a physics-based phase field approach, where the three-dimensional time-dependent Ginzburg-Landau (TDGL) equation and Poisson's equation are self-consistently solved with the SPICE simulator. Systematically calibrated based on the experimental measurements, the model well captures transient negative capacitance in pulse switching dynamics, with domain interaction and viscosity being the key parameters. It is found that the influence of p…
This paper reports the fatigue and retention behavior for Al1-xBxN thin films, a member of the novel family of wurtzite ferroelectrics, with an emphasis on the role of capacitor architecture. By modifying the capacitor architecture, and thus thermal and electrical boundary conditions, we create insight regarding the relative importance of intrinsic and extrinsic contributors to the degradation tendencies. Our experiments suggest that bipolar cycling of metal (Pt/W)/Al0.93B0.07N/W/Al2O3 film stacks first induced wake-up, then a region of constant switchable polarization. On additional cycling, …
In this work, we analyze the ferroelectric (FE) domain-wall (DW) induced negative capacitance (NC) effect in Metal-FE-Insulator-Metal (MFIM) and Metal-FE-Insulator-Semiconductor (MFIS) stacks. Our analysis is based on 2D phase field simulations. Considering HZO as the FE material, we study 180 FE domain formation in MFIM and MFIS stacks and their voltage-dependent DW motion. Our analysis signifies that, when FE is in multi-domain (MD) state with soft-DW, the stored energy in the DW leads to non-hysteretic NC effect in FE, which provides an enhanced charge response in the MFIM stack, compared t…
