Exploring New Metal Electrodes for Ferroelectric Aluminum-Doped Hafnium Oxide

Ryu, Hojoon; Xu, Kai; Kim, Jinhong; Kang, Sangmin; Guo, Ji; Zhu, Wenjuan

doi:10.1109/ted.2019.2907070

Cited by 37 publications

(30 citation statements)

References 26 publications

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“…To date, studies utilizing symmetric platinum electrodes have demonstrated wake-up only when cycling at large fields (e.g., 3.2–4.0 MV cm –1 ), , while lower fields of 2 MV cm –1 have been observed to cause fatigue immediately upon field cycling of devices with palladium electrodes . Studies with non-noble elemental contacts, such as nickel or tungsten, for which oxygen vacancy contributions are less well studied, also exhibit fatigue under cycling fields of 2 MV cm –1 . , While these prior data suggest trends exist for the impact of field magnitude on wake-up versus fatigue response, the origin of the field dependence on these effects is not yet fully understood. Regardless, it is evident that electrode chemistry impacts HfO 2 -based ferroelectric performance.…”

Section: Introductionmentioning

confidence: 99%

Phase-Exchange-Driven Wake-Up and Fatigue in Ferroelectric Hafnium Zirconium Oxide Films

Fields

Smith

Ryan

et al. 2020

ACS Appl. Mater. Interfaces

119

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Ferroelectric hafnium zirconium oxide holds great promise for a broad spectrum of complementary metal–oxide–semiconductor (CMOS) compatible and scaled microelectronic applications, including memory, low-voltage transistors, and infrared sensors, among others. An outstanding challenge hindering the implementation of this material is polarization instability during field cycling. In this study, the nanoscale phenomena contributing to both polarization fatigue and wake-up are reported. Using synchrotron X-ray diffraction, the conversion of non-polar tetragonal and polar orthorhombic phases to a non-polar monoclinic phase while field cycling devices comprising noble metal contacts is observed. This phase exchange accompanies a diminishing ferroelectric remanent polarization and provides device-scale crystallographic evidence of phase exchange leading to ferroelectric fatigue in these structures. A reduction in the full width at half-maximum of the superimposed tetragonal (101) and orthorhombic (111) diffraction reflections is observed to accompany wake-up in structures comprising tantalum nitride and tungsten electrodes. Combined with polarization and relative permittivity measurements, the observed peak narrowing and a shift in position to lower angles is attributed, in part, to a phase exchange of the non-polar tetragonal to the polar orthorhombic phase during wake-up. These results provide insight into the role of electrodes in the performance of hafnium oxide-based ferroelectrics and mechanisms driving wake-up and fatigue, and demonstrate a non-destructive means to characterize the phase changes accompanying polarization instabilities.

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Section: Introductionmentioning

confidence: 99%

Phase-Exchange-Driven Wake-Up and Fatigue in Ferroelectric Hafnium Zirconium Oxide Films

Fields

Smith

Ryan

et al. 2020

ACS Appl. Mater. Interfaces

119

View full text Add to dashboard Cite

show abstract

“…IGZO as an oxide semiconductor can be a suitable solution because it has a clear interface without interdiffusion between the IGZO and HZO. − The ferroelectricity of HfO 2 -based materials is usually obtained via TiN capping layer deposition on HZO and subsequent annealing. Various capping metals (W, Pt, Au, Pd, and Ta) have also been explored. , Besides, an oxide electrode RuO 2 can solve common side effects (fatigue, wake-up effect, domain pinning, and imprint) of ferroelectrics because it may serve as an oxygen vacancy reservoir, while the reactive TiN can be easily oxidized into TiO x N y or TiO 2 at the interface between HfO 2 and TiN . However, the electrode/ferroelectric/electrode structure is a two-terminal device with limited applicability.…”

Section: Igzo-based Electronic- And/or Photonic-synaptic Devicesmentioning

confidence: 99%

“…Various capping metals (W, Pt, Au, Pd, and Ta) have also been explored. 171,172 Besides, an oxide electrode RuO 2 can solve common side effects (fatigue, wakeup effect, domain pinning, and imprint) of ferroelectrics because it may serve as an oxygen vacancy reservoir, while the reactive TiN can be easily oxidized into TiO x N y or TiO 2 at the interface between HfO 2 and TiN. 173 However, the electrode/ ferroelectric/electrode structure is a two-terminal device with limited applicability.…”

Section: Igzo-based Electronic-and/ormentioning

confidence: 99%

Amorphous InGaZnO (a-IGZO) Synaptic Transistor for Neuromorphic Computing

Jang

Park

Kang

et al. 2022

ACS Appl. Electron. Mater.

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Brain-inspired neuromorphic computing emulates the biological functions of the human brain to achieve highly intensive data processing with low power consumption. In particular, spiking neural networks (SNNs) that consist of artificial synapses can process spatiotemporal information while enabling energy-efficient neuromorphic computations. Artificial synapses are a key element of sophisticated neuromorphic hardware, so a significant amount of research has been conducted to develop various materials and device structures. Of these, we assess amorphous InGaZnO (IGZO)-based synaptic transistors that have exhibited properties suitable for emerging hybrid optoelectronic neuromorphic systems. Here, we describe the fundamental principles of neuromorphic computations, neuron circuits, and synaptic devices according to recent studies. IGZO-based transistors are discussed, from their material properties to various device physics for electronic- and/or photonic-neuromorphic systems with extraordinary biological emulations.

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“…In addition, eliminating the nonferroelectric Al 2 O 3 layer also helps reduce the depolarization field and enhance the retention time of the polarization. The retention time of the polarization in ferroelectric HfO 2 can exceed ten years [28]. The ferroelectric HZO films with high remanent polarization and long retention can provide reliable and low power storage of the target signals, enabling the in-memory analog computing in these devices.…”

Section: A Tunable Polarization and Dirac Voltage In Ferroelectric Gmentioning

confidence: 99%

Nonconventional Analog Comparators Based on Graphene and Ferroelectric Hafnium Zirconium Oxide

Liu

Ryu

Zhu

2021

IEEE Trans. Electron Devices

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Unlike transitional semiconductors, graphene has zero bandgap and symmetric electron/hole transport, which leads to unique V-shaped transfer characteristics. Using this property, we design and demonstrate a new type of comparator, which can calculate the absolute distance between two signals, |A − B|, directly. Dual-gate graphene transistors with ferroelectric hafnium zirconium oxide are fabricated to serve as the basic units of the comparators. We show that the remanent polarization of the ferroelectric hafnium oxide can reach ∼30 µC/cm 2 and the output current of the comparator can serve as a scalar indicator of the similarity level between two signals. The embedded ferroelectric layer can store the reference signal in situ, which will reduce the energy consumption and latency related to the data transport. Furthermore, we demonstrate the feasibility of using ferroelectric graphene comparator in image classification and motion detection. Using the k-nearest neighbors (KNNs) algorithm, we show that the graphene comparator arrays can recognize the handwritten digits in the modified national institute of standards and technology (MNIST) data set with over 80% accuracy. These ferroelectric graphene comparators will have broad applications in robotics, security system, self-driving vehicles, and sensor networks.

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Exploring New Metal Electrodes for Ferroelectric Aluminum-Doped Hafnium Oxide

Cited by 37 publications

References 26 publications

Phase-Exchange-Driven Wake-Up and Fatigue in Ferroelectric Hafnium Zirconium Oxide Films

Phase-Exchange-Driven Wake-Up and Fatigue in Ferroelectric Hafnium Zirconium Oxide Films

Amorphous InGaZnO (a-IGZO) Synaptic Transistor for Neuromorphic Computing

Nonconventional Analog Comparators Based on Graphene and Ferroelectric Hafnium Zirconium Oxide

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