Learning Abilities Achieved by a Single Solid‐State Atomic Switch

Hasegawa, Tsuyoshi; Ohno, Takeo; Terabe, Kazuya; Tsuruoka, Tohru; Nakayama, Tomonobu; Gimzewski, James K.; Aono, Masakazu

doi:10.1002/adma.200903680

Cited by 296 publications

(257 citation statements)

References 24 publications

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Section: Introductionmentioning

confidence: 99%

“…Moreover, memristors can function as stateful Boolean logic gates via the material implication operation [15]. In addition, memristors can also be used for neuromorphic computing [16,17] because of their analog switching, and some hybrid circuits due to their ease of stacking [18,19].Among all the kinds of switching materials that have been reported, oxides are the most extensively studied [4]. The interfaces between the metal electrodes and the oxide play a crucial role, especially for bipolar switches [5,6,20].…”

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Metal/TiO2 interfaces for memristive switches

et al. 2011

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The interfaces between metal electrodes and the oxide in TiO 2 -based memristive switches play a key role in the switching as well as in the I -V characteristics of the devices in different resistance states. We demonstrate here that the work function of the metal electrode has a surprisingly minor effect in determining the electronic barrier at the interface. In contrast, Ti oxides can be readily reduced by most electrode metals. The amount of oxygen vacancies created by these chemical reactions essentially determines the electronic barrier at the device interfaces.The memristor, the fourth fundamental passive circuit element [1][2][3], has a wide variety of potential applications based on its promising device properties [1][2][3][4][5][6][7], including non-volatility, fast switching (<10 ns), low energy (∼1 pJ/operation), multiple-state operation, scalability and stackability. As suggested by the name, memristors can be used for information storage [8][9][10][11][12][13][14]. Moreover, memristors can function as stateful Boolean logic gates via the material implication operation [15]. In addition, memristors can also be used for neuromorphic computing [16,17] because of their analog switching, and some hybrid circuits due to their ease of stacking [18,19].Among all the kinds of switching materials that have been reported, oxides are the most extensively studied [4]. The interfaces between the metal electrodes and the oxide play a crucial role, especially for bipolar switches [5,6,20]. Under an applied electric field, oxygen vacancies can drift into the interface region, reducing the electronic barrier and resulting in a low-resistance state. Under an electric field with the opposite polarity, the oxygen vacancies are repelled away from the interface region, recovering the electronic barrier to regain the high resistance state [6,21,22]. A family of nanodevices with different switching and currentvoltage (I -V ) characteristics has been demonstrated by manipulating the elemental composition at the two interfaces of a simple metal/oxide/metal device stack [23]. For a crossbar array of memristors in a storage/memory circuit, sneak path currents [24] can be minimized by using memristors with a rectifying I -V characteristic, especially when they are in the low-resistance state. Therefore, interface engineering is critical to obtain the desired switching behavior and electrical properties for memristive devices.From a semiconductor physics point of view, the work function of the electrode metal might be an important factor in determining the electronic barrier at the metal/oxide interface [25]. This barrier in our thin film devices is not a traditional Schottky barrier because the oxide film is amorphous with a large concentration of defects and likely thinner than the depletion region of the semiconducting oxide. We prepared a set of 5 µm × 5 µm cross-point devices with six different top electrode metals (Au, Pt, Ag, Ni, W and Ti) to examine the effect of these contacts on the I -V characteristics, as show...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Metal/TiO2 interfaces for memristive switches

et al. 2011

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“…29,30 In addition, multilevel memory states will enable more delicate mimicking of short-term and long-term memories in the human neuromorphic system. 27,28 …”

Section: Introductionmentioning

confidence: 99%

“…The working principle of this memory effect is highly similar to that of a neuromorphic system in the human neural network. 27,28 Therefore, ionic devices have attracted renewed interest to mimic the neuromorphic systems and to develop neuromorphic devices, so-called neuristors.…”

Section: Introductionmentioning

confidence: 99%

Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

Lee

MacManus‐Driscoll

2017

APL Materials

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This review provides the design principles to develop new nanoionic applications using vertically aligned nanostructured (VAN) thin films, incorporating two phases which self-assemble in one film. Tunable nanoionics has attracted great attention for energy and device applications, such as ion batteries, solid oxide fuel cells, catalysts, memories, and neuromorphic devices. Among many proposed device architectures, VAN films have strong potential for nanoionic applications since they show enhanced ionic conductivity and tunability. Here, we will review the recent progress on state-of-the-art nanoionic applications, which have been realized by using VAN films. In many VAN systems made by the inclusion of an oxygen ionic insulator, it is found that ions flow through the vertical heterointerfaces. The observation is consistent with structural incompatibility at the vertical heteroepitaxial interfaces resulting in oxygen deficiency in one of the phases and hence to oxygen ion conducting pathways. In other VAN systems where one of the phases is an ionic conductor, ions flow much faster within the ionic conducting phase than within the corresponding plain film. The improved ionic conduction coincides with much improved crystallinity in the ionically conducting nanocolumnar phase, induced by use of the VAN structure. Furthermore, for both cases Joule heating effects induced by localized ionic current flow also play a role for enhanced ionic conductivity. Nanocolumn stoichiometry and strain are other important parameters for tuning ionic conductivity in VAN films. Finally, double-layered VAN film architectures are discussed from the perspective of stabilizing VAN structures which would be less stable and hence less perfect when grown on standard substrates.

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“…6,7 Memristive systems, as theoretically defined by Leon Chua in 1970s, 8,9 are expected to achieve the learning abilities and neuromophic computing where the synaptic function is required. 6,[10][11][12][13] The first memristor found by Strukov et al in 2008 works in the way that the interface barrier is modulated by the evolution of these thermally-reduced titanium oxides. 6,7 It is also demonstrated lately that the diffusion of "adhesion layer" Ti metal atoms through the contact Pt electrode controls the memristive switching, as these diffused Ti atoms lead to the local thermally-derived TiO x .…”

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confidence: 99%

Redox-controlled memristive switching in the junctions employing Ti reactive electrodes

Xia

et al. 2011

AIP Advances

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We have proposed a kind of memristive device based on the junctions employing Ti as the reactive electrodes. The role of electrically-derived redox of Ti in such memristive switching is shown. The structural and chemical evidence of the electrically-derived oxidation is presented by TEM and XPS experiment, respectively. Due to the redox of the top electrode Ti and the consequent drift of oxygen vacancies, the device shows two distinct resistance states under a sweeping voltage loading. ON state is controlled by tunneling process, while OFF state is controlled by Schottky emission conductive mechanism. The failure behaviors of such memristive junctions are also discussed. In the light of the redox principle, we demonstrate that the devices could be recovered by loading a long electrical reduction treatment

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Learning Abilities Achieved by a Single Solid‐State Atomic Switch

Cited by 296 publications

References 24 publications

Metal/TiO2 interfaces for memristive switches

Metal/TiO2 interfaces for memristive switches

Research Update: Fast and tunable nanoionics in vertically aligned nanostructured films

Redox-controlled memristive switching in the junctions employing Ti reactive electrodes

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