arXiv subjects

Revanth Koduru

Publications and source records attributed to Revanth Koduru.

5 recordsLinked to original sources

arXiv2025

Reverse Designing Ferroelectric Capacitors with Machine Learning-based Compact Modeling

Machine learning-based compact models provide a rapid and efficient approach for estimating device behavior across multiple input parameter variations. In this study, we introduce two reverse-design algorithms that utilize these compact models to identify device parameters corresponding to desired electrical characteristics. The algorithms effectively determine parameter sets, such as layer thicknesses, required to achieve specific device performance criteria. Significantly, the proposed methods are uniquely enabled by machine learning-based compact modeling; alternative computationally intensive approaches, such as phase-field modeling, would impose impractical time constraints for iterative design processes. Our comparative analysis demonstrates a substantial reduction in computation time when employing machine learning-based compact models compared to traditional phase-field methods, underscoring a clear and substantial efficiency advantage. Additionally, the accuracy and computational efficiency of both reverse-design algorithms are evaluated and compared, highlighting the practical advantages of machine learning-based compact modeling approaches.

cs.ET↗

arXiv2025

Thickness Dependence of Coercive Field in Ferroelectric Doped-Hafnium Oxide

Ferroelectric hafnium oxide (${HfO_2}$) exhibits a thickness-dependent coercive field $(E_c)$ behavior that deviates from the trends observed in perovskites and the predictions of Janovec-Kay-Dunn (JKD) theory. Experiments reveal that, in thinner $HfO_2$ films ($<100\,nm$), $E_c$ increases with decreasing thickness but at a slower rate than predicted by the JKD theory. In thicker films, $E_c$ saturates and is independent of thickness. Prior studies attributed the thick film saturation to the thickness-independent grain size, which limits the domain growth. However, the reduced dependence in thinner films is poorly understood. In this work, we expound the reduced thickness dependence of $E_c$, attributing it to the anisotropic crystal structure of the polar orthorhombic (o) phase of $HfO_2$. This phase consists of continuous polar layers (CPL) along one in-plane direction and alternating polar and spacer layers (APSL) along the orthogonal direction. The spacer layers decouple adjacent polar layers along APSL, increasing the energy barrier for domain growth compared to CPL direction. As a result, the growth of nucleated domains is confined to a single polar plane in $HfO_2$, forming half-prolate elliptical cylindrical geometry rather than half-prolate spheroid geometry observed in perovskites. By modeling the nucleation and growth energetics of these confined domains, we derive a modified scaling law of $E_c \propto d^{-1/2}$ for $HfO_2$ that deviates from the classical JKD dependence of $E_c \propto d^{-2/3}$. The proposed scaling agrees well with the experimental trends in coercive field across various ferroelectric $HfO_2$ samples.

cond-mat.mtrl-sci↗

arXiv2024

Experimental Investigation of Variations in Polycrystalline Hf0.5Zr0.5O2 (HZO)-based MFIM

Device-to-device variations in ferroelectric (FE) hafnium oxide (HfO2)-based devices pose a crucial challenge that limits the otherwise promising capabilities of this technology. Although previous simulation-based studies have identified polarization (P) domain nucleation and polycrystallinity as key contributors to variations in HfO2, experimental validation remains limited. Here, we experimentally investigate variations in remanent polarization (PR) of Hf0.5Zr0.5O2 (HZO)-based metal-ferroelectric-insulator-metal (MFIM) capacitors across different set voltages (VSET) and FE thicknesses (TFE). Our measurements reveal a non-monotonic behavior of the standard deviation of PR with VSET peaking around coercive voltage (VC), which is consistent with previous simulation-based predictions. In the low- and high-VSET regions, PR variations are primarily dictated by saturation polarization (PS) variations, mainly originating from charge trap effects at the interface between the FE-dielectric (DE) layer and the polycrystallinity of FE. On the other hand, in the mid-VSET region peak, the PR variations are attributed to the VC variation, which comes from a combined effect of multi-domain (MD) P switching and polycrystallinity. Notably, sharp P switching associated with domain nucleation amplifies the variations, resulting in a peak of PR variations in this VSET range. Further, we observe that as HZO thickness (TFE) is scaled, the non-monotonicity in variations with VSET is reduced, primarily due to reduced domain nucleation and smaller grain sizes. We experimentally establish a strong correlation of PR with PS in the low- and high-VSET regions and with VC in the mid-VSET region across various TFE. Finally, our experimental findings are corroborated with simulations using a 3D phase-field model.

physics.app-ph↗

arXiv2024

Small Signal Capacitance in Ferroelectric HZO: Mechanisms and Physical Insights

This study presents a theoretical investigation of the physical mechanisms governing small signal capacitance in ferroelectrics, focusing on Hafnium Zirconium Oxide. Utilizing a time-dependent Ginzburg Landau formalism-based 2D multi-grain phase-field simulation framework, we simulate the capacitance of metal-ferroelectric-insulator-metal (MFIM) capacitors. Our simulation methodology closely mirrors the experimental procedures for measuring ferroelectric small signal capacitance, and the outcomes replicate the characteristic butterfly capacitance-voltage behavior. We delve into the components of the ferroelectric capacitance associated with the dielectric response and polarization switching, discussing the primary physical mechanisms - domain bulk response and domain wall response - contributing to the butterfly characteristics. We explore their interplay and relative contributions to the capacitance and correlate them to the polarization domain characteristics. Additionally, we investigate the impact of increasing domain density with ferroelectric thickness scaling, demonstrating an enhancement in the polarization capacitance component (in addition to the dielectric component). We further analyze the relative contributions of the domain bulk and domain wall responses across different ferroelectric thicknesses. Lastly, we establish the relation of polarization capacitance components to the capacitive memory window (for memory applications) and reveal a non-monotonic dependence of the maximum memory window on HZO thickness.

cond-mat.mtrl-sci↗

arXiv2023

Phase-field Simulations of Polarization Variations in Polycrystalline Hf0.5Zr0.5O2 based MFIM: Voltage-Dependence and Dynamics

In this work, we investigate the device-to-device variations in remanent polarization of Hafnium-Zirconium-Oxide based Metal-Ferroelectric-Insulator-Metal (MFIM) stacks. We consider the effects of polycrystallinity in conjunction with multi-domain effects in HZO to understand the dependencies of variations on static and dynamic voltage stimuli using our 3D dynamic multi-grain phase-field simulation framework. We examine the trends in variations due to various design factors - set voltage, pulse amplitude and pulse width and correlate them to the dynamics of polarization switching and the underlying mechanisms. According to our analysis, variations exhibit a non-monotonic dependence on set voltage due to the interplay between voltage-dependent switching mechanisms and the polycrystalline structure. We further report that towards the higher end of the set voltages, collapsing of oppositely polarized domains can lead to increase in variations. We also show that ferroelectric thickness scaling lowers the device-to-device variations. In addition, considering the dynamics of polarization switching, we signify the key role of voltage and temporal dependence of domain nucleation in dictating the trends in variations. Finally, we show that to reach a target mean polarization, using a pulse with lower amplitude for longer duration results in lower variations compared to higher amplitude pulse for a shorter duration.

physics.comp-ph↗