Two-Step Reset in the Resistance Switching of the Al/TiO<sub><i>x</i></sub>/Cu Structure

Shao, Xing Long; Zhao, Jiahao; Zhang, Kai L.; Chen, Ran; Sun, Kuo; Chen, Chang J.; Liu, Kai; Zhou, Li Wei; Wang, Jian Y.; Ma, Chen M.; Yoon, Kyung Jean; Hwang, Cheol Seong

doi:10.1021/am403498q

Cited by 30 publications

(15 citation statements)

References 25 publications

(39 reference statements)

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“…Therefore, in this work, only the NFSs were focused on afterward. Besides, in one of the previous works of the group of Shao et al, a Cu CF and a Magnéli phase CF were simultaneously formed when the Cu electrode was positively biased in the Al/200 nm thick TiO x /Cu memory cell. In that case, the TiO x film was reactively sputtered using a metal Ti target, making the structure quite porous.…”

Section: Resultsmentioning

confidence: 89%

“…These diverse types of switching behaviors are ascribed to the rich chemical nature of the TiO 2 containing numerous Magnéli phases composed of Ti n O 2 n −1 ( n = 3, 4, 5…) and the relatively easy V O formation in the TiO 2 matrix. It has also been reported that TiO 2 plays the role of an electrolyte in the Al/TiO 2 /Cu ReRAM structure, where the ECM was mediated by the normal conical‐shaped Cu CF. These findings mean that TiO 2 is a highly intriguing material for various ReRAM applications, but they also imply that the involvement of mechanisms other than ECM can interfere with the resistance switching in the presumably ECM cell, such as the Pt/TiO 2 /Cu devices in this work.…”

Section: Introductionmentioning

confidence: 90%

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Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device

Kim

Yoon

Park

et al. 2017

Adv Elect Materials

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and rupture of the metallic conducting filament (CF) composed of active metal atoms, typically Ag and Cu, are responsible for the resistance switching. Unlike other resistive switching devices, the active metal constitutes one of the electrodes which is critically involved in the redox reaction of CF formation and rupture in ECM devices. According to the conventional ECM theory, the cations generated from the anode (active metal) migrate through the solid electrolyte layer when a positive bias is applied to the active metal electrode. The migrated metal cations receive electrons at the cathode (inert metal)/electrolyte interface, and are reduced to metal atoms forming the growing CF. After a series of reduction processes, metallic CF(s) is (are) formed, and current flows through them, thus, the device resistance state becomes a low resistance state (LRS), which corresponds to set switching. When the bias polarity is reversed, a reverse reaction occurs, and the device turns back to a high resistance state (HRS), which is most probably mediated by the oxidation of the metal atoms at the filament tip near the active metal electrode. This corresponds to reset switching. In this conventional ECM model based on the redox reaction of active metal atoms, the idea that a conical-shaped filament grows from the cathode/ electrolyte interface toward the active electrode (anode) and that ECM devices show bipolar resistive switching (BRS) has been widely accepted. [6,7] However, counterarguments against the conventional ECM filament forming theory, covering not only the reset polarity but also the filament geometry, have been discovered in recent years. [8,9] These studies revealed that the filament growth can be extensively influenced by the detailed material parameters, such as the type of electrolyte materials as well as the cation/electron mobility and its redox rate. [9][10][11][12][13] With the aid of in situ transmission electron microscopy (TEM) and conductive atomic force microscopy techniques, real-time image of growth and rupture of conducting filament have been reported. [14,15] These factors contribute not only to the initiation location of the filament growth but also to the consequent shape of the grown filament. In addition, studies objecting to the incumbent ECM reset mechanism theory have been reported recently. According to the conventional ECM theory, due to its redox reaction based characteristics, only bipolarThe electrochemical metallization (ECM) cell is a feasible contender for high density resistance switching random access memory or neuromorphic devices. This work elucidates the detailed switching model based on the Cu conducting filament (CF) configuration and the interplay between the Joule heating and electric field effects in the Pt/TiO 2 /Cu ECM cell, which can explain the switching behaviors both in accordance and discordance with the conventional ECM theory. The Cu CF configuration is varied from the conventional conical one for a small compliance current (I cc , ≈1 mA) to the hourglass or eve...

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Section: Resultsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 90%

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device

Kim

Yoon

Park

et al. 2017

Adv Elect Materials

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“…However, as the resistance-switching random access memory (RRAM) is becoming one of the leading contenders for the next-generation non-volatile memory, SiO 2 along with other highly diverse metal oxides were tested as active resistance-switching (RS) layers. Several transition metal oxides (TMOs), such as TiO 2 , NiO, Ta 2 O 5 , and HfO 2 , have been tested as RS layers because the multi-valence nature of the transition metals would render the RS in these materials easily achieved 1 2 3 4 . Additionally, the so-called voltage-time dilemma from typical RS materials triggered interest in finding alternative RS materials, and several groups had tested SiO 2 5 6 7 .…”

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confidence: 99%

Bias-polarity-dependent resistance switching in W/SiO2/Pt and W/SiO2/Si/Pt structures

Jiang

Chen

et al. 2016

Sci Rep

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SiO2 is the most significantly used insulator layer in semiconductor devices. Its functionality was recently extended to resistance switching random access memory, where the defective SiO2 played an active role as the resistance switching (RS) layer. In this report, the bias-polarity-dependent RS behaviours in the top electrode W-sputtered SiO2-bottom electrode Pt (W/SiO2/Pt) structure were examined based on the current-voltage (I-V) sweep. When the memory cell was electroformed with a negative bias applied to the W electrode, the memory cell showed a typical electronic switching mechanism with a resistance ratio of ~100 and high reliability. For electroforming with opposite bias polarity, typical ionic-defect-mediated (conducting filament) RS was observed with lower reliability. Such distinctive RS mechanisms depending on the electroforming-bias polarity could be further confirmed using the light illumination study. Devices with similar electrode structures with a thin intervening Si layer between the SiO2 and Pt electrode, to improve the RS film morphology (root-mean-squared roughness of ~1.7 nm), were also fabricated. Their RS performances were almost identical to that of the single-layer SiO2 sample with very high roughness (root-mean-squared roughness of ~10 nm), suggesting that the reported RS behaviours were inherent to the material property.

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“…20 To obtain multi-level states in this case, a thin film of 3 nm AlO x with high bandgap (9 eV) 21 is used to increase R HRS and hinder hole injection from Al(TE). For Al/AlO x /VO x /Cu device, segmented I-V characteristics can be observed in set/reset process, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Metallization and Trapping/Detrapping Resistive Switching Mechanism in Al/VOx/Cu RRAM

Zhang

Sun

Wang

et al. 2014

ECS Solid State Letters

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We investigated resistive switching mechanism in Al/VO x /Cu RRAM structure. The temperature dependence of resistance on low resistive state (LRS) and conductive atomic force microscopy (CAFM) measurement confirmed the formation and rupture of Cu conductive filaments (Cu-CF) in VO x dielectric. Cu-CF was formed after a trapping process (HRS→LRS) and ruptured at Schottky junction Al/VO x interface (LRS→HRS) judged by rectification and C-V characteristics of high resistive state (HRS). A model combining trapping/detrapping and Cu-CF formation/rupture is proposed to describe resistive switching mechanism. Based on the combined resistive switching mechanism, an application of multi-level states in Al/AlO x /VO x /Cu device is achieved successfully.Resistance random access memory (RRAM) has attracted a great deal of attention owing to its high speed, low power consumption and high density. 1-4 Solid electrolyte of binary metal oxide for electrochemical metallization memory (ECM) has got much research interest due to its simple structure and excellent resistive switching characteristics. 5-7 The electrochemical metal filament generation and dissolution is widely accepted as the mechanism for ECM cells, such as Cu or Ag electrode based RRAM. 8 Metal filament formation from anode to cathode and rupture in cathode interface are observed in Cu/ZrO 2 /Pt structure by transmission electron microscopy (TEM). 9 The filament rupture in cathode interface in ZnO-based RRAM is also proven by current-voltage (I-V) characteristics in the off-states with different cathode electrode materials. 10 However, the cathode filament rupture mechanism remains to be clarified. In our previous work, resistive switching characteristic of VO x -based RRAM with Cu electrode has been reported. 11,12 In this paper, we investigated resistive switching mechanism in Al/VO x /Cu RRAM structure. We find that a trapping process occurs ahead of Cu-CF formation through I-V characteristics in set process, Cu-CF ruptures at Al/VO x interface judging from the rectification and C-V characteristics of HRS. Then we propose a resistive switching model combining trapping/detrapping and Cu-CF formation/rupture for Al/VO x /Cu structure. An application of multi-level states in Al/AlO x /VO x /Cu device has been achieved based on the combined resistive switching mechanism. ExperimentalThe experimental samples were prepared as follows. Structure of Al/VO x /Cu was fabricated on Ti/SiO 2 /Si substrates. A 200 nm Cu bottom electrode (BE) was deposited with electron beam evaporation on the substrates. Then 70 nm VO x film was sputtered on Cu film by radio frequency (RF) magnetron sputtering of V 2 O 5 ceramic target in ambient of Ar and O 2 with flow rates of 64 sccm and 16 sccm respectively. After that, 200 nm top electrodes (TE) of Al and Cu were deposited subsequently on the different area of same VO x film by electron beam evaporation and patterned by a metal mask with diameter of 400 μm, therefore forming Al/VO x /Cu and Cu/VO x /Cu structures (Fig. 1a). Finally, oth...

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Two-Step Reset in the Resistance Switching of the Al/TiO_x/Cu Structure

Cited by 30 publications

References 25 publications

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device

Bias-polarity-dependent resistance switching in W/SiO2/Pt and W/SiO2/Si/Pt structures

Electrochemical Metallization and Trapping/Detrapping Resistive Switching Mechanism in Al/VOx/Cu RRAM

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Two-Step Reset in the Resistance Switching of the Al/TiOx/Cu Structure

Cited by 30 publications

References 25 publications

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO2/Cu Electrochemical Metallization Device

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO2/Cu Electrochemical Metallization Device

Bias-polarity-dependent resistance switching in W/SiO2/Pt and W/SiO2/Si/Pt structures

Electrochemical Metallization and Trapping/Detrapping Resistive Switching Mechanism in Al/VOx/Cu RRAM

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Product

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Two-Step Reset in the Resistance Switching of the Al/TiO_x/Cu Structure

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device