Nondestructive Readout Complementary Resistive Switches Based on Ferroelectric Tunnel Junctions

Xi, Zhongnan; Chen, Kewei; Wen, Zheng

doi:10.1021/acsami.7b18363

Cited by 21 publications

(13 citation statements)

References 43 publications

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“…This results in low tunneling current and high resistance values. Whereas high resistance is desirable for some applications, for instance, in ferroelectric complementary resistive switching devices, 49,50 a sizable current is required to achieve fast and reliable reading operation of memory devices, and a trade-off needs to be found. 3 Different strategies can be followed to reduce the device resistance: first is to use metals with a lower work function to reduce the tunneling barrier height (at the expense of usually higher reactivity of the metal); second is to stimulate Fowler− Nordheim tunneling (at the expense of requiring higher reading voltages); 51 and third is to reduce the barrier thickness.…”

Section: ■ Introductionmentioning

confidence: 99%

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Polarization and Resistive Switching in Epitaxial 2 nm Hf_0.5Zr_0.5O₂ Tunnel Junctions

Sulzbach

Tan

Estandía

et al. 2021

ACS Appl. Electron. Mater.

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In the quest for reliable and power-efficient memristive devices, ferroelectric tunnel junctions are being investigated as potential candidates. Complementary metal oxide semiconductor-compatible ferroelectric hafnium oxides are at the forefront. However, in epitaxial tunnel devices with thicknesses around ≈4−6 nm, the relatively high tunnel energy barrier produces a large resistance that challenges their implementation. Here, we show that ferroelectric and electroresistive switching can be observed in ultrathin 2 nm epitaxial Hf 0.5 Zr 0.5 O 2 (HZO) tunnel junctions in large area capacitors (≈300 μm 2 ). We observe that the resistance area product is reduced to about 160 and 65 Ω•cm 2 for OFF and ON resistance states, respectively. These values are 2 orders of magnitude smaller than those obtained in equivalent 5 nm HZO tunnel devices while preserving a similar OFF/ON resistance ratio (210%). The devices show memristive and spike-timing-dependent plasticity behavior and good retention. Electroresistance and ferroelectric loops closely coincide, signaling ferroelectric switching as a driving mechanism for resistance change.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polarization and Resistive Switching in Epitaxial 2 nm Hf_0.5Zr_0.5O₂ Tunnel Junctions

Sulzbach

Tan

Estandía

et al. 2021

ACS Appl. Electron. Mater.

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“…In FTJs, the devices adopting n-type Nb:SrTiO 3 (Nb:STO) semiconductors as bottom electrodes have shown improved resistance switching performances because the ferroelectric field effect-induced Schottky barriers on the Nb:STO surfaces can efficiently modulate electron transports. − Giant LRS/HRS current ratios up to ∼10 7 have been reported in Pt/BTO/Nb:STO, Ag/BTO/Nb:STO, and Pt/Sm-doped BiFeO 3 /Nb:STO tunnel junction devices at room temperature. − However, resistance switching with hysteretic current–voltage ( I – V ) loops have also been observed in devices with nonferroelectric barriers due to electrical control of charged defects, for example, the metallization of insulator layers with trap states in Au/YBa 2 Cu 3 O 7 /LaAlO 3 /Nb:STO, the migration of oxygen vacancies in metal/STO/Nb:STO, , and the charge trapping/detrapping at the interface of Pt/Nb:STO and YBa 2 Cu 3 O 6+ x /Nb:STO devices. − These results suggest the complexity of Nb:STO-based resistive devices and also make the role of ferroelectricity in resistance switching properties unclear. In this work, we carry out a comparative study between the ferroelectric Pt/BTO/Nb:STO and the nonferroelectric Pt/STO/Nb:STO and Pt/LaAlO 3 /Nb:STO tunnel junctions to clarify the effects of ferroelectric polarization on resistive memory properties.…”

Section: Introductionmentioning

confidence: 99%

The Role of Ferroelectric Polarization in Resistive Memory Properties of Metal/Insulator/Semiconductor Tunnel Junctions: A Comparative Study

Yang

et al. 2020

ACS Appl. Mater. Interfaces

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Recently, tunnel junction devices adopting semiconducting Nb:SrTiO3 electrodes have attracted considerable attention for their potential applications in resistive data storage and neuromorphic computing. In this work, we report on a comparative study of Pt/insulator/Nb:SrTiO3 tunnel junctions between ferroelectric BaTiO3 and nonferroelectric SrTiO3 and LaAlO3 barriers to reveal the role of polarization in resistance switching properties. Although hysteretic behaviors appear in current–voltage measurements of all devices regardless of the barrier character, significantly improved current ratios by more than three orders of magnitude are observed in the Pt/BaTiO3/Nb:SrTiO3 tunnel junctions due to the dominance of polarization in modulation of junction barrier profiles between the low and high resistance states. The switchable polarization also gives rise to enhanced resistance retention since the electron diffusion that smears the barrier contrast of the bistable resistance states is suppressed by the polar BaTiO3/Nb:SrTiO3 interface associated with the ferroelectric bound charges. These polarization-induced effects are absent in the nonferroelectric Pt/SrTiO3/Nb:SrTiO3 and Pt/LaAlO3/Nb:SrTiO3 devices in which serious resistance state decay, described by Fick’s second law, is observed since there are no switchable interface charges on SrTiO3/Nb:SrTiO3 and LaAlO3/Nb:SrTiO3 to block the electron diffusion. In addition, the Pt/BaTiO3/Nb:SrTiO3 device also exhibits an excellent switching endurance up to ∼4.0 × 106 bipolar cycles. These enhancements indicate the importance of ferroelectric polarization for achieving high-performance resistance switching and suggest that metal/ferroelectric/Nb:SrTiO3 tunnel junctions are promising candidates for nonvolatile memory applications.

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“…Therefore, it appears that Nb:STO has limited potential in CRS applications. In addition, CRS devices based on ferroelectric tunnel junctions with Schottky‐barrier‐controlled responses show gradual HRS/LRS and LRS/HRS transitions rather than abrupt as it would be required for optimal suppression of the sneak current issue . Therefore, other approaches are required to create integrable ferroelectric‐based CRS.…”

Section: Introductionmentioning

confidence: 99%

Complementary Resistive Switching Using Metal–Ferroelectric–Metal Tunnel Junctions

Qian

Fina

Sánchez

et al. 2019

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devices can be scaled down as required by the most aggressive scaling in electronic industry. This is an important advantage compared with electronic memory devices based on electric charge storage. [1][2][3] In fact, the resistive random access memory (RRAM) elements are intensively investigated on the path toward higher memory density and enhanced computing performance, as demanded by present and future information technologies. The socalled passive crossbar array of RS devices constitutes the backbone of RRAMs and reconfigurable logics, and holds promises to become central in the quest for merging logic and memory functions or neuromorphic computing. [4][5][6][7] The crossbar array consists of an array of parallel bottom metallic electrodes and a perpendicular array of top metallic electrodes (so called, word and bit lines) that sandwich at each crossing point, the RS element. By applying suitable voltage at the specified word and bit lines, the state of an RS element is set to LRS (ON) or HRS (OFF). Inherent to this array configuration is that the bottom electrode connects all elements in a row and the top electrode connects all elements in a column. It thus follows that: i) if several elements are in LRS state, when current is used to probe the state of a particular element, charge will leak across all LRS elements (sneak current) thus compromising the reading and ii) the presence of LRS states implies a permanent current leakage and a concomitant Joule dissipation. These intrinsic bottlenecks of crossbar arrays are well recognized and several approaches, such as integration of strongly rectifying elements, [8] were proposed to overcome this drawback. In 2010, Linn et al. [9] proposed a simple solution to solve the sneak problem: connect two RS devices in anti-serial configuration in such a way that if one is in LRS state the other is in the HRS state (so-called complementary resistive switching, CRS). In these circumstances, information is stored not in the state of a single RS element but in the state of distinguishable coupled pair: LRS+HRS and HRS+LRS, representing different logic states ("0" and "1"). Of relevance is that the resulting coupled state is always in a HRS at remanence and thus the sneak and leakage currents are reduced.This novel approach was successfully demonstrated using a variety of materials and RS mechanisms. For instance, it was demonstrated in Pt/SiO 2 /GeSe/Cu [9] and in all-oxides RRAMs. [10][11][12][13][14][15][16] In this approach, data reading is achieved by Complementary resistive switching (CRS) devices are receiving attention because they can potentially solve the current-sneak and current-leakage problems of memory arrays based on resistive switching (RS) elements. It is shown here that a simple anti-serial connection of two ferroelectric tunnel junctions, based on BaTiO 3 , with symmetric top metallic electrodes and a common, floating bottom nanometric film electrode, constitute a CRS memory element. It allows nonvolatile storage of binary states ("1" = "HRS+LRS" and "0" =...

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Nondestructive Readout Complementary Resistive Switches Based on Ferroelectric Tunnel Junctions

Cited by 21 publications

References 43 publications

Polarization and Resistive Switching in Epitaxial 2 nm Hf_0.5Zr_0.5O₂ Tunnel Junctions

Polarization and Resistive Switching in Epitaxial 2 nm Hf_0.5Zr_0.5O₂ Tunnel Junctions

The Role of Ferroelectric Polarization in Resistive Memory Properties of Metal/Insulator/Semiconductor Tunnel Junctions: A Comparative Study

Complementary Resistive Switching Using Metal–Ferroelectric–Metal Tunnel Junctions

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Nondestructive Readout Complementary Resistive Switches Based on Ferroelectric Tunnel Junctions

Cited by 21 publications

References 43 publications

Polarization and Resistive Switching in Epitaxial 2 nm Hf0.5Zr0.5O2 Tunnel Junctions

Polarization and Resistive Switching in Epitaxial 2 nm Hf0.5Zr0.5O2 Tunnel Junctions

The Role of Ferroelectric Polarization in Resistive Memory Properties of Metal/Insulator/Semiconductor Tunnel Junctions: A Comparative Study

Complementary Resistive Switching Using Metal–Ferroelectric–Metal Tunnel Junctions

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Polarization and Resistive Switching in Epitaxial 2 nm Hf_0.5Zr_0.5O₂ Tunnel Junctions

Polarization and Resistive Switching in Epitaxial 2 nm Hf_0.5Zr_0.5O₂ Tunnel Junctions