Ferroelectric Tunneling Junctions Based on Aluminum Oxide/ Zirconium-Doped Hafnium Oxide for Neuromorphic Computing

Ryu, Hojoon; Wu, Haonan; Rao, Fubo; Zhu, Wenjuan

doi:10.1038/s41598-019-56816-x

Cited by 159 publications

(127 citation statements)

References 37 publications

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“…Furthermore, GM2 and GM2A8 solution showed pronounced triple helix conformations after cooling. This was in accordance with results of other studies investigating sequential GM hydrogels 8 , 28 , 29 in which a 0.2 mg mL −1 solution in distilled water was cooled for 2 h at 4 °C 28 , 29 or a 0.1% (w/v) solution was cooled for 1 h at 4 °C 8 .…”

Section: Resultssupporting

confidence: 92%

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Differentiation of physical and chemical cross-linking in gelatin methacryloyl hydrogels

Rebers

Reichsöllner

Regett

et al. 2021

Sci Rep

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Gelatin methacryloyl (GM) hydrogels have been investigated for almost 20 years, especially for biomedical applications. Recently, strengthening effects of a sequential cross-linking procedure, whereby GM hydrogel precursor solutions are cooled before chemical cross-linking, were reported. It was hypothesized that physical and enhanced chemical cross-linking of the GM hydrogels contribute to the observed strengthening effects. However, a detailed investigation is missing so far. In this contribution, we aimed to reveal the impact of physical and chemical cross-linking on strengthening of sequentially cross-linked GM and gelatin methacryloyl acetyl (GMA) hydrogels. We investigated physical and chemical cross-linking of three different GM(A) derivatives (GM10, GM2A8 and GM2), which provided systematically varied ratios of side-group modifications. GM10 contained the highest methacryloylation degree (DM), reducing its ability to cross-link physically. GM2 had the lowest DM and showed physical cross-linking. The total modification degree, determining the physical cross-linking ability, of GM2A8 was comparable to that of GM10, but the chemical cross-linking ability was comparable to GM2. At first, we measured the double bond conversion (DBC) kinetics during chemical GM(A) cross-linking quantitatively in real-time via near infrared spectroscopy-photorheology and showed that the DBC decreased due to sequential cross-linking. Furthermore, results of circular dichroism spectroscopy and differential scanning calorimetry indicated gelation and conformation changes, which increased storage moduli of all GM(A) hydrogels due to sequential cross-linking. The data suggested that the total cross-link density determines hydrogel stiffness, regardless of the physical or chemical nature of the cross-links.

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Section: Resultssupporting

confidence: 92%

“…These results were consistent with another CD study of GMs of Zhu et al . showing that an increasing DM increased the random polypeptide chain conformation and decreased the triple helix conformation 28 . Furthermore, Zhu et al .…”

Section: Resultsmentioning

confidence: 93%

Differentiation of physical and chemical cross-linking in gelatin methacryloyl hydrogels

Rebers

Reichsöllner

Regett

et al. 2021

Sci Rep

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“…Similar to this work, bilayer systems with HZO/AlO ferroelectric/dielectric structures were recently reported [ 34 , 35 ]. Unlike the dielectric, ferroelectric (or antiferroelectric)-related layers such as ZrO 2 serving as a seed layer were introduced to promote the orthorhombic phase in the doped HfO 2 film [ 36 , 37 ].…”

Section: Resultssupporting

confidence: 82%

Ferroelectric Switching in Trilayer Al2O3/HfZrOx/Al2O3 Structure

Kang

Kim

et al. 2020

Micromachines

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Since ferroelectricity has been observed in simple binary oxide material systems, it has attracted great interest in semiconductor research fields such as advanced logic transistors, non-volatile memories, and neuromorphic devices. The location in which the ferroelectric devices are implemented depends on the specific application, so the process constraints required for device fabrication may be different. In this study, we investigate the ferroelectric characteristics of Zr doped HfO2 layers treated at high temperatures. A single HfZrOx layer deposited by sputtering exhibits polarization switching after annealing at a temperature of 850 °C. However, the achieved ferroelectric properties are vulnerable to voltage stress and higher annealing temperature, resulting in switching instability. Therefore, we introduce an ultrathin 1-nm-thick Al2O3 layer at both interfaces of the HfZrOx. The trilayer Al2O3/HfZrOx/Al2O3 structure allows switching parameters such as remnant and saturation polarizations to be immune to sweeping voltage and pulse cycling. Our results reveal that the trilayer not only makes the ferroelectric phase involved in the switching free from pinning, but also preserves the phase even at high annealing temperature. Simultaneously, the ferroelectric switching can be improved by preventing leakage charge.

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“…The ferroelectric capacitor alternatively denoted as ferroelectric tunnel junction (FTJ) was also used as a stand-alone memory. [92,93,96] Unlike the FeFET-based synapse, where the conductance from the source to drain is adjusted by polarization change occurring in the ferroelectric oxide between the gate and silicon substrate, conductance through the FTJ is directly affected by up or down direction of the dipole. The conductance of the FTJ is transmitted smoothly by the identical pulse.…”

Section: Ferroelectric Memory/mrammentioning

confidence: 99%

“…The charge on the capacitor represented the synaptic weight, and it was elaborately varied by the gate voltage for charging and discharging to the capacitor node. However, intrinsic volatile - [96] a)…”

Section: Novel Hybrid Synaptic Configurationmentioning

confidence: 99%

Recent Advancements in Emerging Neuromorphic Device Technologies

Woo

Kim

et al. 2020

Advanced Intelligent Systems

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The explosive growth of data and information has motivated technological developments in computing systems that utilize them for efficiently discovering patterns and gaining relevant insights. Inspired by the structure and functions of biological synapses and neurons in the brain, neural network algorithms that can realize highly parallel computations have been implemented on conventional silicon transistor‐based hardware. However, synapses composed of multiple transistors allow only binary information to be stored, and processing such digital states through complicated silicon neuron circuits makes low‐power and low‐latency computing difficult. Therefore, the attractiveness of the emerging memories and switches for synaptic and neuronal elements, respectively, in implementing neuromorphic systems, which are suitable for performing energy‐efficient cognitive functions and recognition, is discussed herein. Based on a literature survey, recent progress concerning memories shows that novel strategies related to materials and device engineering to mitigate challenges are presented to primarily achieve nonvolatile analog synaptic characteristics. Attempts to emulate the role of the neuron in various ways using compact switches and volatile memories are also discussed. It is hoped that this review will help direct future interdisciplinary research on device, circuit, and architecture levels of neuromorphic systems.

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Ferroelectric Tunneling Junctions Based on Aluminum Oxide/ Zirconium-Doped Hafnium Oxide for Neuromorphic Computing

Cited by 159 publications

References 37 publications

Differentiation of physical and chemical cross-linking in gelatin methacryloyl hydrogels

Differentiation of physical and chemical cross-linking in gelatin methacryloyl hydrogels

Ferroelectric Switching in Trilayer Al2O3/HfZrOx/Al2O3 Structure

Recent Advancements in Emerging Neuromorphic Device Technologies

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