Epitaxial orthorhombic Hf0.5Zr0.5O2 (HZO) films on La0.67Sr0.33MnO3 (LSMO) electrodes show robust ferroelectricity, with high polarization, endurance and retention. However, no similar results have been achieved using other perovskite electrodes so...

Insertion of layers displaying field-induced metal-to-insulator (M/I) transition in ferroelectric tunnel junctions (FTJs) has received attention as a potentially useful way to enlarge junction tunnel electroresistance (TER). Half-doped manganites being at the verge of metal-insulator character are thus good candidates to be slave layers in FTJs. However, the phase diagram of these oxides is extremely sensitive to strain and thus can be radically different when integrated in epitaxial FTJs. Here we report a systematic study of large-area (A = 4 to 100 m 2 ) Pt/La0.5Sr0.5MnO3/BaTiO3/La0.7Sr0.3MnO3 (Pt/HD/BTO/LSMO) FTJs, having different thicknesses of the ferroelectric (2-3nm) and HD layers (1-2nm), grown on substrates imposing either tensile (SrTiO3) or compressive (LaAlO3) strains. Room-temperature electric characterization of the FTJs shows polarization-controlled ON/ OFF states. Clear evidences of field-induced M/I transition (difference between junction resistance in OFF and ON state is increased of more than one order of magnitude) are observed in junctions prepared on SrTiO3 but the HD layer is generally metallic on LaAlO3. Moreover, the M/I transition is only confined in an interfacial layer of the slave film thus entailing an overall reduction of TER. The orderly results reported here give some hints towards selection of HD materials and substrates for optimal FTJ responsiveness.

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...

Advanced use of ferroelectric capacitors in data storage and computing relies on the control of their electrical resistance (electroresistance, ER) by the change of the electrostatic potential profile across the capacitor occurring upon electric field–driven polarization switching. Here it is reported the observation that BaTiO3‐based capacitors, sandwiched between Pt and La2/3Sr1/3MnO3 electrodes, display a large ER, whose magnitude (near 104% at room temperature) and sign (ER > 0, ER < 0) are determined by the writing pulse duration and temperature. Temperature‐dependent measurements have been instrumental to obtain evidence of the presence of a thermally activated process coexisting with the electronic changes produced by ferroelectric polarization switching, both contributing to ER. Detailed analysis allows concluding that the thermally activated process can be attributed to field‐assisted ionic motion. It is argued that the relative balance between purely electronic and ionic diffusion processes modulate the height of the interfacial Schottky barriers and, consequently, are responsible for the observed variations of magnitude and sign of ER.

The ferroelectric phase of HfO2 is generally stabilized in polycrystalline films, which typically exhibit the highest polarization when deposited using low oxidizing conditions. In contrast, epitaxial film grown by pulsed...