Stefan Slesazeck

• Dr.-Ing.
• Senior Researcher at NaMLab GmbH

The pristine state of hafnium based ferroelectric devices exhibits various unwanted properties, such as imprint and peak splitting, which diminish with bipolar cycling. The incorporation of a niobium oxide layer at different positions in metal-ferroelectric-metal and metal-ferroelectric-insulator-metal stacks is used to modify the pristine state of...

This manuscript presents the first and simplest ever‐reported electrical cell, which leverages one memristor on Edge of Chaos to reproduce the three‐bifurcation cascade, marking the entire life cycle from birth to extinction via All‐to‐None effect of an electrical spike, also referred to as Action Potential, across axon membranes under monotonic mo...

Ferroelectric tunnel junctions (FTJs) are a class of memristor which promise low-power, scalable, field-driven analog operation. In order to harness their full potential, operation with identical pulses is targeted. In this paper, several weight update schemes for FTJs are investigated, using either non-identical or identical pulses, and with time...

The roadmap is organized into several thematic sections, outlining current computing challenges, discussing the neuromorphic computing approach, analyzing mature and currently utilized technologies, providing an overview of emerging technologies, addressing material challenges, exploring novel computing concepts, and finally examining the maturity...

Fluorite‐structured ferroelectrics are one of the most promising material systems for emerging memory technologies. However, when integrated into electronic devices, these materials exhibit strong imprint effects that can lead to a failure during writing or retention operations. To improve the performance and reliability of these devices, it is car...

The well‐developed high‐k technologies ease the integration complexity for HfO2‐based ferroelectric (FE) devices in the complementary metal‐oxide semiconductor processes. Sputtered HfxZr(1‐x)O2 (HZO) FEs have proven their thermal compatibility in back‐end‐of‐line (BEOL) integration processes with high remanent polarization (Pr) and a high cycling e...

In artificial neural networks, the “synaptic weights” connecting the neurons are adjusted during the training. Beyond silicon, functionalizing the back‐end‐of‐line (BEOL) of CMOS circuits with novel materials is a key enabler for deploying neural network accelerators. The hardware implementation of the synaptic weights requires linear and reprogram...

The discovery of ferroelectricity in hafnia has revolutionized the field and brought industry applications closer than ever. One of the most interesting aspects of hafnia compared to other ferroelectric materials is the possibility of scaling film thicknesses down to the 10 nm regime and even below. However, going significantly below 10 nm poses so...

Ferroelectric hafnium and zirconium oxides have undergone rapid scientific development over the last decade, pushing them to the forefront of ultralow-power electronic systems. Maximizing the potential application in memory devices or supercapacitors of these materials requires a combined effort by the scientific community to address technical limi...

While technologically challenging, the integration of ferroelectric thin films with graphene spintronics potentially allows the realization of highly efficient, electrically tunable, nonvolatile memories through control of the interfacial spin–orbit driven interaction occurring at graphene/Co interfaces deposited on heavy metal supports. Here, the...

Computing systems are becoming more and more power-constrained due to unconventional computing requirements like computing on the edge, in-sensor, or simply an insufficient battery. Emerging Non-Volatile Memories are explored to build low-power computing circuits, and adders are one among them. In this work, we propose a low-power adder using a Fer...

Due to the voltage driven switching at low voltages combined with nonvolatility of the achieved polarization state, ferroelectric materials have a unique potential for low power nonvolatile electronic devices. The competitivity of such devices is hindered by compatibility issues of well‐known ferroelectrics with established semiconductor technology...

The presented measurement procedure in (Engl et al., 2023) is used to characterize the degradation of the hysteresis-free charge amplification in unipolar operation of stabilized negative capacitance capacitors. Two degradation processes, namely, remanent switching of domains and a change in the internal electric bias field, can be shown with this...

This article (DOI: 10.1002/inf2.12380) comprehensively reviews the recent progress in artificial synaptic and spiking neuron devices for neuromorphic computing based on (Hf,Zr)O2‐based ferroelectrics. The actual human brain consists of neurons, axons, and synapses. Simply explain their functions, neurons communicate with each other via electrical e...

Reconfigurable field effect transistors are an emerging class of electronic devices, which exploit a structure with multiple independent gates to selectively adjust the charge carrier transport. Here, we propose a new device variant, where not only p-type and n-type operation modes, but also an ambipolar mode can be selected solely by adjusting a s...

Event-based neuromorphic systems provide a low-power solution by using artificial neurons and synapses to process data asynchronously in the form of spikes. Ferroelectric Tunnel Junctions (FTJs) are ultra low-power memory devices and are well-suited to be integrated in these systems. Here, we present a hybrid FTJ-CMOS Integrate-and-Fire neuron whic...

A continuous exponential rise has been observed in the storage and processing of the data that may not curtail in the foreseeable future. The required data processing speed and power consumption are restricted by the buses between the logic and memory devices that are characteristic of the von Neumann computing architecture. Bio‐mimicking neuromorp...

HfO2-based ferroelectric tunnel junctions (FTJs) exhibit attractive properties for adoption in neuromorphic applications. The combination of ultra-low-power multi-level switching capability together with the low on-current density suggests the application in circuits for massive parallel computation. In this work, we discuss one example circuit of...

In this paper, the self-heating effect for multi-finger fully depleted SOI nMOSFETs is investigated. The layout parameters of the transistor are varied, and the conductance-based method is used for the extraction of the thermal resistance. An empirical-based scalable thermal resistance model that accounts for geometrical layout parameters is develo...

Direct integration of ferroelectric Hf0.5Zr0.5O2 (HZO) on the inert surface of graphene is challenging. Here, using nucleation layers to promote atomic layer deposition of HZO was investigated. Different metals were deposited as nucleation layers via dc sputtering. Ta, which oxidizes in air to form a sub-stoichiometric oxide, was compared to Pt, wh...

A measurement technique is presented to quantify the polarization loss in ferroelectric thin films as a function of delay time during the first 100s after switching. This technique can be used to investigate charge trapping in ferroelectric thin films by analyzing the magnitude and rate of polarization loss. Exemplary measurements have been perform...

A measurement technique is presented to quantify the polarization loss in ferroelectric thin films as a function of delay time during the first 100s after switching. This technique can be used to investigate charge trapping in ferroelectric thin films by analyzing the magnitude and rate of polarization loss. Exemplary measurements have been perform...

Emerging nonvolatile memory technologies are attracting interest from the system design level to implement alternatives to conventional von-Neumann computing architectures. In particular, the hafnium oxide-based ferroelectric (FE) memory technology is fully CMOS-compatible and has already been used for logic-in-memory architectures or compact terna...

Ferroelectric field effect transistor (FeFET) memory has shown the potential to meet the requirements of the growing need for fast, dense, low-power, and non-volatile memories. In this paper, we propose a memory architecture named crossed-AND (C-AND), in which each storage cell consists of a single ferroelectric transistor. The write operation is p...

Modern computation based on the von Neumann architecture is today a mature cutting-edge science. In the Von Neumann architecture, processing and memory units are implemented as separate blocks interchanging data intensively and continuously. This data transfer is responsible for a large part of the power consumption. The next generation computer te...

This manuscript provides a comprehensive tutorial on the operating principles of a bio-inspired Cellular Nonlinear Network, leveraging the local activity of NbOx memristors to apply a spike-based computing paradigm, which is expected to deliver such a separation between the steady-state phases of its capacitively-coupled oscillators, relative to a...

In this work advanced TCAD (Technology Computer Aided Design) modeling will be used aiming at investigating the potentiality of Negative Capacitance (NC) devices in non-conventional application domains (e.g., radiation detection). A device-level approach to simulate the electrical characteristics of ferroelectric Hf0.5Zr0.5O2 (HZO) has been develop...

Crystalline materials with broken inversion symmetry can exhibit a spontaneous electric polarization, which originates from a microscopic electric dipole moment. Long-range polar or anti-polar order of such permanent dipoles gives rise to ferroelectricity or antiferroelectricity, respectively. However, the recently discovered antiferroelectrics of...

Novel non-volatile memory devices based on ferroelectric thin films represent a promising emerging technology that is ideally suited for neuromorphic applications. The physical switching mechanism in such films is the nucleation and growth of ferroelectric domains. Since this has a strong dependence on both pulse width and voltage amplitude, it is...

The shift towards a distributed computing paradigm, where multiple systems acquire and elaborate data in real-time, leads to challenges that must be met. In particular, it is becoming increasingly essential to compute on the edge of the network, close to the sensor collecting data. The requirements of a system operating on the edge are very tight:...

This work aims to investigate the suitability of innovative negative capacitance (NC) devices to be used in High Energy Physics experiments detection systems, featuring self-amplified, segmented, high granularity detectors. Within this framework, MFM (Metal-Ferroelectric-Metal) and MFIM (Metal-Ferroelectric-Insulator-Metal) structures have been inv...

Ferroelectric field effect transistor (FeFET) memory has shown the potential to meet the requirements of the growing need for fast, dense, low-power, and non-volatile memories. In this paper, we propose a memory architecture named crossed-AND (C-AND), in which each storage cell consists of a single ferroelectric transistor. The write operation is p...

Ferroelectricity is a material property that can be used for binary information storage and as such is promising for adoption in non-volatile memories. Ferroelectric materials feature two non-zero spontaneous polarization states that can be reversed by application of an external electrical field. Already in 1952 first realizations of ferroelectric...

In this letter, p-type ferroelectric field-effect-transistors (FeFETs) based on HfO2 and embedded in GlobalFoundries 28 nm bulk high-k metal gate (HKMG) technology (28SLPe) are systematically investigated and compared to their n-type counterparts. We show that the two device types, based on Si channel, exhibit a symmetric memory window (MW) and ver...

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 fer...

In this article, we review the recent progress of ferroelectric field-effect transistors (FeFETs) based on ferroelectric hafnium oxide (HfO2), ten years after the first report on such a device. With a focus on the use of FeFET for nonvolatile memory application, we discuss its basic operation principles, switching mechanisms, device types, material...

Ferroelectric field-effect transistors (FeFETs) with a single gate structure and using the newly discovered ferroelectric hafnium oxide as an active material are attracting considerable interest for nonvolatile memory devices. However, such FeFETs struggle to achieve a large separation between the two logic states (memory window, MW) because of the...

Although technologically challenging, the integration of ferroelectric thin films with graphene spintronics potentially allows the realization of highly efficient, electrically tuneable, non-volatile memories. Here, the atomic layer deposition (ALD) of ferroelectric Hf$_{0.5}$Zr_${0.5}$O$_2$ (HZO) directly on graphene (Gr)/Co/heavy metal (HM) epita...

Doping of HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin films is a powerful means for stabilizing ferroelectricity in this material. Yet, the amount of doping is critical to achieving the best ferroelectric response. This article investigates the impact of the Si doping content on th...

Emerging non-volatile memories are getting new interest in the system design community. They are used to design logic-in-memory circuits and propose alternatives to von-Neuman architectures. Hafnium oxide-based based ferroelectric memory technology, which is fully compatible with CMOS technologies is particularly interesting for logic-in-memory des...

Ferroelectric tunneling junctions (FTJ) are considered to be the intrinsically most energy efficient memristors. In this work, specific electrical features of ferroelectric hafnium-zirconium oxide based FTJ devices are investigated. Moreover, the impact on the design of FTJ-based circuits for edge computing applications is discussed by means of two...

Ferroelectric tunnel junctions (FTJ) based on hafnium zirconium oxide (Hf1-xZrxO2; HZO) are a promising candidate for future applications, such as low-power memories and neuromorphic computing. The tunneling electroresistance (TER) is tunable through the polarization state of the HZO film. To circumvent the challenge of fabricating thin ferroelectr...

Modern computation based on the von Neumann architecture is today a mature cutting-edge science. In this architecture, processing and memory units are implemented as separate blocks interchanging data intensively and continuously. This data transfer is responsible for a large part of the power consumption. The next generation computer technology is...

Crystalline materials with broken inversion symmetry can exhibit a spontaneous electric polarization, which originates from a microscopic electric dipole moment. Long-range polar or anti-polar order of such permanent dipoles gives rise to ferroelectricity or antiferroelectricity, respectively. However, the recently discovered antiferroelectrics of...

Local activity is the capability of a system to amplify infinitesimal fluctuations in energy. Complex phenomena, including the generation of action potentials in neuronal axon membranes, may never emerge in an open system unless some of its constitutive elements operate in a locally active regime. As a result, the recent discovery of solid-state vo...

Ferroelectrics are a class of materials that possess a variety of interactions between electrical, mechanical, and thermal properties that have enabled a wealth of functionalities. To realize integrated systems, the integration of these functionalities into semiconductor processes is necessary. To this end, the complexity of well-known ferroelectri...

The main focus of this paper is the presentation of reliable methods for the determination of the optimum coloring of a graph, commonly known in the literature as vertex coloring problem. It has been shown that networks of capacitively coupled oscillators can be used to solve vertex coloring problems. In this paper we address the negative impact of...

Scaling of planar HfO2-based ferroelectric capacitors is investigated experimentally by varying the capacitor area within five orders of magnitude, under the scope of a limited thermal budget for crystallization. Both Hf0.5Zr0.5O2 (HZO) and Si-doped HfO2 (HSO)-based metal/ferroelectric/metal capacitors with a 10 nm dielectric film thickness and TiN...

Ferroelectric hafnium oxide (HfO2) has been extensively studied for over a decade, especially as a CMOS-compatible material in emerging memory applications. Most recently, it has gained a lot of attention for being applied in the field of beyond von-Neumann computing. The specific nature of different nonvolatile storage elements, particularly ferro...

Negative capacitance in ferroelectric materials has been suggested as a solution to reduce the power dissipation of electronics beyond fundamental limits. The discovery of ferroelectricity and negative capacitance in the widely used class of HfO2-based materials has since sparked large research efforts to utilize these effects in ultra-low power tr...

Accumulative switching (AS) in ferroelectric field-effect transistors (FeFETs), which takes place under a train of subcritical voltage pulses, represents not only a concern in terms of disturbs for classical nonvolatile memory but also a source of novel opportunities for neuromorphic applications. Here, we report a detailed experimental investigati...

Second harmonic generation (SHG) and frequency mixing of electrical signals are fundamental for a wide range of radiofrequency applications. Recently, ferroelectric field-effect transistors (FeFETs), made from ferroelectric hafnium oxide (HfO2), have demonstrated promising SHG capabilities due to their unique symmetric transfer curves. In this lett...

Ferroelectric tunnel junctions have recently attracted a lot of research interest, not only for memory operation but also for e.g. neuromorphic computing. Retention characteristics of these devices are of utmost importance in many applications. The authors have recently demonstrated the feasibility of double‐layered ferroelectric tunnel junctions w...

Progress towards low-power electronics based on negative capacitance has been slow. For the field to develop, the gap between fundamental research on ferroelectric materials and the engineering of practical devices needs to be bridged.

This letter investigates the impact of read operation on the electrical properties of hafnium oxide-based ferroelectric field-effect transistors (FeFETs). We report that a quasi-static read may induce a series of phenomena, including a severe underestimation of the memory window, undesirable loss of the stored state, i.e. destructive read, increase...

Long data retention is a critical requirement for many of the potential applications of HfO₂-based ferroelectric field-effect transistors (FeFETs). However, methods for its rapid assessment are still missing. In this article, we report a detailed investigation of the retention and switching properties of FeFETs fabricated in the 28-nm high-k metal...

Frequency multiplication is essential in wireless communication systems, where stable high-frequency oscillations are required. However, multipliers typically employ power- and area-hungry filtering and amplification circuits. Here, we show that a single ferroelectric field-effect transistor, made from ferroelectric hafnium oxide, can be used as a...

From our own experience in the group, we know that there is quite a gap to bridge between scientists focused on basic material research and their counterparts in a close-to-application community focused on identifying and solving final technological and engineering challenges. In this review, we try to provide an easy-to-grasp introduction to the f...

Due to their CMOS compatibility, hafnium oxide based ferroelectric field-effect transistors (FeFET) gained remarkable attention recently, not only in the context of nonvolatile memory applications but also for being an auspicious candidate for novel combined memory and logic applications. In addition to bringing nonvolatility into existing logic ci...

Charge sharing poses a fundamental problem in the design of dynamic logic gates, which is nearly as old as digital circuit design itself. Although, many solutions are known, up to now most of them add additional complexity to a given circuit and require careful optimization of device sizes. Here we propose a simple CMOS-technology compatible transi...

Neuromorphic engineering represents one of the most promising computing paradigms for overcoming the limitations of the present-day computers in terms of energy efficiency and processing speed. While traditional neuromorphic circuits are based on complementary metal oxide semiconductor (CMOS) transistors and large capacitors, the recently emerging...

The recent advent of ferroelectricity in thin hafnium oxide films has enabled an unprecedented scaling of ferroelectric field-effect transistors (FeFETs) based on this material. However, the small-area devices, which have the channel length of only a few tens of nanometers, show some striking performance differences when compared to the large-area...