Asymmetric Resistive Switching Dynamics in BaTiO₃ Tunnel Junctions

Abstract

microstructural effects should play a major role on the time-dependent dynamics of the polarization switching. [23][24][25] Most commonly, asymmetric electrodes exist in ferroelectric capacitors either because of different metals are used or because the nature of the corresponding metal/ferroelectric and ferroelectric/metal interfaces is different. Thus, asymmetric polarization switching for the positive and the negative bias can occur, as experimentally observed. [22,[26][27][28][29][30] When referring to the resistive switching controlled by ferroelectric polarization, the same arguments given above suggest that the HRS-to-LRS and LRS-to-HRS processes could also be different, implying an asymmetric response when reversing the polarity of the writing electric fields. Understanding and controlling these effects are pivotal to exploit the potential multistate of the ferroelectric memristive device. Even more, a detailed knowledge on the resistive switching dynamics is crucial for ferroelectric tunnel junction's implementation in neuromorphic circuits, where time-dependent action potentials trigger the synapse responses. [31] In the particular case of ferroelectric tunnel barriers, Chanthbouala et al. [17] pioneeringly reported on the impact of the polarization switching dynamics on the measured change of resistance (so-called electroresistance, ER, or tunnel electroresistance, TER). These authors observed that under a given voltage bias larger than the coercive field (at a given measuring frequency) the switching from LRS to HRS was gradual, expanding along a range of voltages. The smooth transition from LRS to HRS was successfully modeled by assuming the contributions of domain nucleation and expansion mechanisms on the domain dynamics. In contrast, the reverse process (HRS to LRS) was observed to be more abrupt. This observation, reminiscent of the asymmetric polarization reversal in ferroelectric capacitors, [22,26,[28][29][30] may imply a different responsivity of LRS and HRS to external stimuli, thus impacting the memristive response depending on the sign of the biasing electric field.Here we focus on the comparison of the resistive transition from LRS to HRS and HRS to LRS in BaTiO 3 (BTO) ferroelectric tunnel junctions, triggered by electric fields of different polarity. We show that the dynamics of polarization and the concomitant resistive switching of the BTO junctions are radically different for both polarizations. The resistive transition from LRS to HRS is smooth, suggesting it is dominated by random nucleation and growth of polar domains. In contrast, the HRSto-LRS transition displays avalanche-like features which depend on the amplitude and frequency of the applied electric field. WeThe resistive switching associated with polarization reversal is studied in detail in ferroelectric BaTiO 3 tunnel junctions, with focus on the dynamics of the ferroelectric domain switching. It is observed that the transition between the high-resistance state (HRS) and the low-resistance state (LRS) is largely asymmetri...

Non-volatile optical switch of resistance in photoferroelectric tunnel junctions

“…3a, b), makes indiscernible the electronic and ionic transport channels. Analogous abrupt change of resistance at V W < 0 was reported in other BTO-based FTJs 53,60 and it was interpreted in terms of ferroelectric domain avalanches stimulated by the asymmetric voltage drop across the junctions. Now, we turn to the electrical characterization of the FTJs under illumination conducted by using blue (λ = 405 nm, E = 3.06 eV) and red (λ = 638 nm, E = 1.94 eV) lasers, near and well below BTO bandgap (E g = 3.3 eV) 61 , respectively.…”

“…3a, b ), makes indiscernible the electronic and ionic transport channels. Analogous abrupt change of resistance at V W < 0 was reported in other BTO-based FTJs 53 , 60 and it was interpreted in terms of ferroelectric domain avalanches stimulated by the asymmetric voltage drop across the junctions.…”

“…11 , 12 ). One might suspect that a slower resistive switching mechanism, not responsive to fast writing pulses (≤500 μs), is related to an ionic migration process 52 , 53 . Taking τ write = 500 μs as the diffusion time of ions across the BTO film thickness to reach the interface under V + C-HIGH ≈ 13 V, a mobility ≈ 2.5 × 10 −9 cm 2 V −1 s −1 is estimated.…”

Unraveling Ferroelectric Polarization and Ionic Contributions to Electroresistance in Epitaxial Hf0.5Zr0.5O2 Tunnel Junctions

“…It has also been shown that by performing minor polarization loops, ferroelectric tunnel devices can store information in different resistive states, mimicking the functioning of a memristive element. [4,5] This approach has been successfully achieved by using ferroelectric perovskites such as BaTiO 3 , [6][7][8][9] Pb(Zr 0.2…”

Current Rectification, Resistive Switching, and Stable NDR Effect in BaTiO3/CeO2 Heterostructure Devices

“…Hence, the device simultaneously containing the resistive switching characteristics and rectification effect is desirable to resolve the conflict between sneak path problems and integration complexity.Resistive switching characteristics have been extensively studied in different materials, such as semiconductor oxides, [5][6][7][8] perovskites, [9,10] chalcogenides, [11][12][13][14][15] and ferroelectrics. [16,17] Although metal oxides have attracted much attention in volatile memory technology but the nonuniformity and stability issues diverted the attention of researchers to other materials. The electric field induced switchable spontaneous polarization in ferroelectric thin films make them a promising candidates for nonvolatile memories.…”