Monitoring Oxygen Movement by Raman Spectroscopy of Resistive Random Access Memory with a Graphene-Inserted Electrode

Tian, He; Chen, Hong Yu; Gao, Bin; Yu, Shimeng; Liang, Jiale; Yang, Yi; Xie, Dan; Kang, Jinfeng; Ren, Tian; Zhang, Yuegang; Wong, H.-S. Philip

doi:10.1021/nl304246d

Cited by 129 publications

(96 citation statements)

References 34 publications

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“…5, Supplementary Table 1 and in Supplementary Methods). As was shown previously for memristive devices with graphene electrodes, we assume that oxygen is removed from the lattice during set and reincorporated during reset19. The low-voltage I – V characteristics of the LRS and HRS are calculated accordingly using static distributions of doubly ionizable donor-type oxygen vacancies in the SrTiO 3 thin film (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Graphene is not only highly conductive, but is also highly photoelectron-transparent and, when used as top electrode, may circumvent this limitation. Graphene electrodes have already been integrated successfully in memristive devices1920, demonstrating improved cycling reproducibility and the potential for low-power operation and (photon)-transparent memories. They have even been found to enable ultra-high-density, cost-effective three-dimensional ReRAM arrays21.…”

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confidence: 99%

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Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes

et al. 2016

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The continuing revolutionary success of mobile computing and smart devices calls for the development of novel, cost- and energy-efficient memories. Resistive switching is attractive because of, inter alia, increased switching speed and device density. On electrical stimulus, complex nanoscale redox processes are suspected to induce a resistance change in memristive devices. Quantitative information about these processes, which has been experimentally inaccessible so far, is essential for further advances. Here we use in operando spectromicroscopy to verify that redox reactions drive the resistance change. A remarkable agreement between experimental quantification of the redox state and device simulation reveals that changes in donor concentration by a factor of 2–3 at electrode-oxide interfaces cause a modulation of the effective Schottky barrier and lead to >2 orders of magnitude change in device resistance. These findings allow realistic device simulations, opening a route to less empirical and more predictive design of future memory cells.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes

et al. 2016

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“…Although the tail of the composition profile is generally ~2 nm in length due to the spatial extent of the electron beam, the lack of Si at the center of the Y2O3 profile and similar slopes for both the Y and O profiles support our premises. These results suggest that the increase in PO2 by HP-PDA are totally spent on the improvement of the crystallinity and the reduction of defects such as oxygen vacancies, rather than on the diffusion of the other elements, because graphene is known to work as a diffusion barrier, [25][26][27] as schematically explained in Fig. 4(d).…”

Section: (C)mentioning

confidence: 99%

Large Fermi energy modulation in graphene transistors with high-pressure O₂-annealed Y₂O₃topgate insulators

et al. 2014

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We demonstrate a considerable suppression of the low-field leakage through a Y2O3 topgate insulator on graphene by applying high-pressure O2 at 100 atm during post-deposition annealing (HP-PDA). Consequently, the quantum capacitance measurement for the monolayer graphene reveals the largest Fermi energy modulation (EF = 0.52 eV, i.e., the carrier density of 2×10 13 cm -2 ) in the solid-state topgate insulators reported so far. HP-PDA is the robust method to improve the electrical quality of high-k insulators on graphene.The deposition of ultrathin and reliable high-k dielectrics on graphene is required to realize the high transconductance in graphene field-effect transistors (FETs). Generally, two kinds of deposition methods are used: one is physical vapor deposition 1-4 (PVD) with low particle energies to avoid the defect introduction in graphene, 5 the other is atomic layer deposition (ALD) with buffer layers 6-8 to overcome the chemically inert surface of graphene. Recently, graphene FETs have been reported with ALD Al2O3 topgate insulators as thin as 2.6 nm. 9 Insulators fabricated by PVD and ALD, however, suffer from the dielectric breakdown at the voltage much lower than the complete breakdown voltage due to the fragility of dielectrics accumulated by the low-field leakage during the iterative measurements. Typical electrical field for this low-field dielectric breakdown is ~0.2 V/nm. This is a critical issue for the reliability of the topgate insulators. A common limitation for the insulators on graphene fabricated by both PVD and ALD is the lack of a robust methodology for post-deposition annealing (PDA) in an O2 atmosphere. Although PDA at a high temperature (e.g., ~500 C) is known to improve the electrical quality of the insulator considerably, 10 it introduces many defects in graphene by oxidation. 11 Here, from a thermodynamic viewpoint, 12 let's consider the Gibbs free energy change (G = G -RTlnPO2) for the oxidation reaction of M + O2 = MO2, where G is the standard Gibbs free energy change for the oxidation reaction, R is gas constant, PO2 is the oxygen partial pressure and M is the metal. G should be negative to facilitate the oxidation. The first term for G can be used for material selection. An appropriate rare-earth element for use in high-k insulators should be highly susceptible to oxidation. Figure 1(a) shows G of rare-earth, transition and representative elements at 300 C calculated using a thermodynamic database. 13 The G for yttrium is negatively largest among all of the metal oxides, even smaller than that of carbon. Therefore, Y2O3 can be obtained at relatively low oxidation temperatures and is thermodynamically stable on graphene. The band gap for Y2O3 is ~5.5 eV, which is almost identical to that of h-BN. 14 The dielectric constant of Y2O3 is ~12, 15 while it is ~3-4 for h-BN. 16 The second term for G is the process condition, which is derived from the oxygen potential. G should be further decreased to reduce the defects in the insulator such as oxygen vacancy. This c...

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“…The resistive switching behavior of VCM has been demonstrated to be closely related to the oxygen vacancy (or ion) migration with the Raman Spectroscopy [4] and X-ray photoelectron spectroscopy (XPS) technologies [5]. In the present work, oxygen vacancy generation, drift and diffusion mechanisms are included in the forming model.…”

Section: Physical Modelmentioning

confidence: 99%

Physical model of electroforming mechanism in oxide-based resistive switching devices (RRAM)

Sun

et al. 2014

2014 12th IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT)

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Resistive switching mechanism is an ongoing topic in resistive random access memory (RRAM) communities. In this work, a physical model including vacancy generation, drift/diffusion mechanisms is developed to characterize the forming process in valence change resistive switching memories (VCM). This model addresses the intrinsic nature of forming time dependence on pulse amplitude and temperature, which is attributed to combined effects of vacancy generation and migration. The microscopic vacancy concentration evolution during forming operation was calculated and the vacancy migration effect on the forming process was quantitatively evaluated. The modeled forming time versus pulse amplitude relationship at different temperatures show excellent agreement with the experiment data.

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Monitoring Oxygen Movement by Raman Spectroscopy of Resistive Random Access Memory with a Graphene-Inserted Electrode

Cited by 129 publications

References 34 publications

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes

Large Fermi energy modulation in graphene transistors with high-pressure O₂-annealed Y₂O₃topgate insulators

Physical model of electroforming mechanism in oxide-based resistive switching devices (RRAM)

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Monitoring Oxygen Movement by Raman Spectroscopy of Resistive Random Access Memory with a Graphene-Inserted Electrode

Cited by 129 publications

References 34 publications

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes

Large Fermi energy modulation in graphene transistors with high-pressure O2-annealed Y2O3topgate insulators

Physical model of electroforming mechanism in oxide-based resistive switching devices (RRAM)

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Large Fermi energy modulation in graphene transistors with high-pressure O₂-annealed Y₂O₃topgate insulators