Coexistence of the bipolar and unipolar resistive-switching modes in NiO cells made by thermal oxidation of Ni layers

Goux, L.; Lisoni, J. G.; Jurczak, M.; Wouters, Dirk J.; Courtade, L.; Müller, Christophe

doi:10.1063/1.3275426

Cited by 178 publications

(120 citation statements)

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“…The reproducible RS is achieved by repeating SET and RESET processes. Although the RS phenomena and their reproducibility were reported and there are many analogical reasoning of reversible RS in metal oxides 2,9,11,12,[14][15][16][17][18][19][20][21][22][23][24] , their switching mechanism has not yet been clarified. To reveal the RS mechanism, direct observations of conducting filaments are required.…”

Section: Introductionmentioning

confidence: 99%

The Observation of “Conduction Spot” on NiO Resistance Random Access Memory

Kondo

Arita

Fujii

et al. 2011

Jpn. J. Appl. Phys.

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We succeeded to observe the "conduction spot" (CS) in the capacitor structure ReRAM, which includes a conductive filament. In this study, we used NiO prepared by thermal oxidation at high temperature as 800°C. It requires a forming process by extra high voltage, which partly removes the top electrode from the resistance switched area.These experiments enabled us to observe the conductive filament directly in CS on NiO ReRAM by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From SEM images, CSs seem to be produced by some kind of breakdown, but we confirmed the reproducible resistance switching at least 50 cycles after the CS generation. By means of energy dispersive X-ray spectroscopy (EDX) with TEM observations, drastic oxygen reduction was recognized in local area within CS of NiO films. Moreover, the CS area depended on the injection power for forming. These experimental data suggest that miniaturization of ReRAM will be achieved by reducing the injection power for forming. *

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Section: Introductionmentioning

confidence: 99%

The Observation of “Conduction Spot” on NiO Resistance Random Access Memory

Kondo

Arita

Fujii

et al. 2011

Jpn. J. Appl. Phys.

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“…This supports the idea that the reset operation occurs based on the oxidation of the filaments. 17,20,21 The forming voltage of various positions selected by the tipshaped TE is summarized in Fig. 4(d), where the horizontal axis denotes the measurement sequence corresponding to time.…”

Section: Influence Of Oxygen In Reram Switchingmentioning

confidence: 99%

“…4,8,[19][20][21] In this section, the oxygen content of the bridge that appeared during forming will be discussed. Figure 3(a) shows a TEM image of the bridge region of the sample shown in Fig.…”

Section: B Oxygen Content Of Bridgementioning

confidence: 99%

“…[10][11][12][13][14][15][16] Recent works reported that the "filamentredox-model" (in short, the "filament model") is influential in unipolar resistance switching. 4,[17][18][19][20][21] In the first process of this ReRAM operation, a relatively high voltage applied to the initial ReRAM film in the high resistance state (HRS, off-state) changes it to the low resistance state (LRS, onstate). This initializing operation is called "forming" and is carried out based on a current limitation (in other words, current compliance) to prevent permanent destruction of the device.…”

Section: Introductionmentioning

confidence: 99%

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In-situ transmission electron microscopy of conductive filaments in NiO resistance random access memory and its analysis

Fujii

Arita

Hamada

et al. 2013

Journal of Applied Physics

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We used thermal oxidization at various temperatures to prepare NiO/Pr-Ir for use in resistance random access memory (ReRAM) samples. In-situ transmission electron microscopy (TEM) was used to investigate the forming process of these ReRAM samples, where a needle-shaped top electrode of Pt-Ir was attached to the NiO/Pt-Ir ReRAM layer. The forming voltage initializing the NiO layer increased at an oxidization temperature of between 200 and 400 C. In this process, conductive bridges, which are thought to be conductive filaments of a ReRAM, appeared, and their sizes showed a correlation with the injection power. It was as small as about 300 nm 2 when the injection power was 10 À6 W. Energy dispersive X-ray spectroscopy was used to analyze the bridge, and it was experimentally confirmed that the oxygen content of the bridge was lower than that of the initial NiO layer. However, these bridges in the low resistance state did not show further ReRAM switching to the high resistance state inside of a TEM instrument. To check the reason of this result, we investigated samples outside of the TEM instrument, which had similar geometry to that of TEM specimens. They showed the ReRAM switching in air ambient but not in vacuum. Combining these results inside and outside of the TEM instrument, it can be concluded that the existence of oxygen around the conductive filament plays an important role. This supports the filament redox model on the ReRAM operation. V C 2013 American Institute of Physics.

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“… In "valence change mechanism", the resistance switching relies on redox electrochemistry that changes the conductivity of the I-layer. Field-induced oxygen vacancies drift plays a predominant role in few specific oxidebased memory elements: TiO2-based "Memristors" [27] recently demonstrated by Hewlett-Packard Company; CMOx TM elements developed by Unity Semiconductor [28]; NiO layers obtained from nickel oxidation in small via structures [29][30][31]. Memory operations require polarity reversal (i.e.…”

Section: Phase Change Memories Pcmmentioning

confidence: 99%