Programmable ferroelectric tunnel memristor

Quindeau, Andy; Hesse, D.; Alexe, Marin

doi:10.3389/fphy.2014.00007

Cited by 19 publications

(24 citation statements)

References 24 publications

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“…While the antiferroelectric tunnel junction does not retain information, it can play the role of a complementary resistive switching device which usually is obtained by antiserially stacking two classical resistive switching layers. [13] The genuine electronic switching of the present antiferroelectric tunnel junctions, along with its ferroelectric counterpart, might be at the core of a new type of resistive switching memories in which multistate and programmable memristive effects [31,32] would have a significant application potential in future cognitive computing. The present antiferroelectric tunnel junctions might enable fabrication of simple crossbar array, since it is known that crossbar array type memory without a strong nonlinearity at each node is practically impossible to develop.…”

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confidence: 99%

Antiferroelectric Tunnel Junctions

Apachitei

Peters

Sanchez

et al. 2017

Adv Elect Materials

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of the TMR sign [7] and magnetoelectric effects including electric control of spin polarization. [8,9] Antiferroelectrics (AFEs) are a special class of polar materials, which possess the respective order parameter at microscopic level, but no net macroscopic polarization. Similar to the antiferromagnetic case, AFEs are formed by neighboring stacks of opposite dipoles that cancel each other in the absence of an electric field, resulting in zero net spontaneous polarization. However, if an external electric field is applied, the local dipoles reorient and, at a certain value of this field, AFEs have a finite macro scopic polarization. The process is usually characterized by a double-hysteresis P(E) loop. Both antiferromagnetic and AFE have been largely overseen for potential use in data storage. Only very recently the antiferromagnetic layers have been successfully employed in data storage devices. [10] Although AFE materials have been used as artificial barrier terminations in FTJ for reducing fatigue and increasing the TER effect, so far no studies were reported on self-standing AFE tunnel junctions. [11,12] Here we introduce antiferroelectric tunnel junctions (AFTJs) exhibiting characteristic double-hysteresis loops in tunnel current, of which TER can reach values as high as 10 9 %, or ON/OFF resistance ratio in tunnel current can reach as large as 10 7 , with the ON state current densities exceeding 10 A cm −2 . The mechanism of the TER effect relies on a field-induced switching from a nonpolar to a polar state, which is characteristic to AFE materials. The giant TER value is thanks to a very low current density in the OFF state, characteristic for a high barrier height, and a high ON current due to a considerable barrier change induced by polarization. Although AFTJs do not retain information since an AFE layer does not have a remnant polarization, they can play a role of complementary resistive switching devices which are usually obtained by antiserially stacking two classical resistive switching layers. [13] Similar to the ferroelectric case, if the thickness of an AFE film sandwiched between two electrodes is in the range of few nanometers, quantum tunneling is significant and rules the current flowing between two electrodes at low applied fields. Since the AFE film does not exhibit any macroscopic polarization, the polarization-induced lowering of the electronic barrier as described by Zhuravlev et al. [3] should be negligible at low applied fields. Once an electric field is sufficiently high, the local dipoles all will reorient in the same direction and will build a net ferroelectric polarization in the field direction, Antiferroelectric tunnel junctions of La 0.7 Sr 0.3 MnO 3 /PbZrO 3 /Co fabricated by pulsed laser deposition and sputtering are reported for the first time. The current-voltage curves highlight the monostability type (threshold) resistive switching corresponding to the antiferroelectric behavior for the PbZrO 3 barrier down to ≈4 nm thickness. Tunneling electroresistance values up to 10 9 ...

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confidence: 99%

Antiferroelectric Tunnel Junctions

Apachitei

Peters

Sanchez

et al. 2017

Adv Elect Materials

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“…As has been shown, switching of the ferroelectric polarization modulates the tunnelling current by more than five orders of magnitude91011 and in combination with magnetic electrodes a multiferroic tunnel junction (MFTJ) is formed. This allows an extra degree of freedom so that MFTJs can be used for four-state memory devices, controlled by both magnetic and electric fields121314, or even controlling spin filtering via ferroelectric polarization15.…”

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Polarization curling and flux closures in multiferroic tunnel junctions

et al. 2016

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Formation of domain walls in ferroelectrics is not energetically favourable in low-dimensional systems. Instead, vortex-type structures are formed that are driven by depolarization fields occurring in such systems. Consequently, polarization vortices have only been experimentally found in systems in which these fields are deliberately maximized, that is, in films between insulating layers. As such configurations are devoid of screening charges provided by metal electrodes, commonly used in electronic devices, it is wise to investigate if curling polarization structures are innate to ferroelectricity or induced by the absence of electrodes. Here we show that in unpoled Co/PbTiO3/(La,Sr)MnO3 ferroelectric tunnel junctions, the polarization in active PbTiO3 layers 9 unit cells thick forms Kittel-like domains, while at 6 unit cells there is a complex flux-closure curling behaviour resembling an incommensurate phase. Reducing the thickness to 3 unit cells, there is an almost complete loss of switchable polarization associated with an internal gradient.

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“…In these ferroelectric tunnel junctions, 2,3 the tunnel resistance varies depending on the orientation of the polarization; this tunnel electroresistance effect enables a non-destructive information readout. [4][5][6] Furthermore, ferroelectric domains and their dynamics 7-10 offer additional degrees of freedom and give rise to an analog memristive response of the tunnel junction [11][12][13][14] that emulates the behavior of synapses in neuromorphic networks. 15,16 Large tunnel electroresistance values of more than 10 3 are now achievable at room temperature, [17][18][19][20][21] which makes ferroelectric tunnel junctions interesting candidates for resistive memories.…”

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Tunnel electroresistance in BiFeO3 junctions: size does matter

Boyn

Douglas

Blouzon

et al. 2016

Applied Physics Letters

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In ferroelectric tunnel junctions, the tunnel resistance depends on the polarization orientation of the ferroelectric tunnel barrier, giving rise to tunnel electroresistance. These devices are promising to be used as memristors in neuromorphic architectures and as non-volatile memory elements. For both applications device scalability is essential, which requires a clear understanding of the relationship between polarization reversal and resistance change as junction size shrinks. Here we show robust tunnel electroresistance in BiFeO 3 -based junctions with diameters ranging from 1200 to 180 nm. We demonstrate that the tunnel electroresistance and the corresponding fraction of reversed ferroelectric domains change 1 Electronic mail: vincent.garcia@thalesgroup.com 2 drastically with the junction diameter: while micron-size junctions display reversal in less than 10% of the area, the smallest junctions show an almost complete polarization reversal.Modeling the electric-field distribution, we highlight the critical role of the bottom electrode resistance which significantly diminishes the actual electric field applied to the ferroelectric barrier in the mixed polarization state. A polarization-dependent critical electric field below which further reversal is prohibited is found to explain the large differences between the ferroelectric switchability of nano-and micron-size junctions. Our results indicate that ferroelectric junctions are downscalable and suggest that specific junction shapes facilitate complete polarization reversal.Ferroelectric materials possess a spontaneous electrical polarization that is switchable by an external electric field. This enables the use of thin ferroelectric films sandwiched between electrodes as non-volatile memories.1 In such ferroelectric memories, the information is encoded by the polarization orientation and recovered in a destructive capacitive readout.When the thickness of the ferroelectric films is of the order of a few nanometers, electron tunneling becomes possible. In these ferroelectric tunnel junctions, 2,3 the tunnel resistance varies depending on the orientation of the polarization; this tunnel electroresistance effect enables a non-destructive information readout. These interfacial magnetoelectric coupling phenomena can be probed by tunnel magnetoresistance experiments, resulting in a non-volatile control of the spin-polarization. 26-29Moreover, selecting oxide electrodes subject to field-induced electronic phase transitions upon polarization reversal may result in enhanced tunnel electroresistance. 29,30 Hence, ferroelectric tunnel junctions offer a fantastic playground to explore electric-field-driven modifications at the nanoscale. 31 Top electrodes of Pt (10 nm) / Co (10 nm) with diameters ranging from 180 nm to 1200 nm ( Fig. 1(a)) are defined by electron-beam lithography, sputtering, and lift-off. 18 We use the conductive tip of an atomic force microscope (AFM) to connect individual top electrodes and perform electric transport measurements under a constant v...

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Programmable ferroelectric tunnel memristor

Cited by 19 publications

References 24 publications

Antiferroelectric Tunnel Junctions

Antiferroelectric Tunnel Junctions

Polarization curling and flux closures in multiferroic tunnel junctions

Tunnel electroresistance in BiFeO3 junctions: size does matter

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