Giant Electroresistance in Ferroionic Tunnel Junctions

Abstract

Summary Oxide-based resistive switching devices, including ferroelectric tunnel junctions and resistance random access memory, are promising candidates for the next-generation non-volatile memory technology. In this work, we propose a ferroionic tunnel junction to realize a giant electroresistance. It functions as a ferroelectric tunnel junction at low resistance state and as a Schottky junction at high resistance state, due to interface engineering through the field-induced migration of oxygen vacancies. An extremely large electroresistance with ON/OFF ratios of 5.1×10 7 at room temperature and 2.1×10 9 at 10 K is achieved, using an ultrathin BaTiO 3-δ layer as the ferroelectric barrier and a semiconducting Nb-doped SrTiO 3 substrate as the bottom electrode. The results point toward an appealing way for the design of high-performance resistive switching devices based on ultrathin oxide heterostructures by ionic controlled interface engineering.

Reproducible Ultrathin Ferroelectric Domain Switching for High‐Performance Neuromorphic Computing

“…We confirmed the dominant role of ferroelectric domain switching in the BTO‐based FTJs grown under high oxygen pressures, by comparing to nonferroelectric SrTiO 3 (STO)‐based devices . Figure a exhibits the evolution of conductance‐voltage ( G–V ) hysteresis loops as the pulse width varies while keeping the voltage range between ‐3.4 and +2.2 V. The conductance of LRS increases gradually as the pulse width increases, and eventually, a saturation value is reached when the pulse width is more than 10 ms.…”

“…Local hysteretic behaviors of the PFM phase and amplitude signals were collected in DART (dual A.C. resonance tracking) mode and the signals were recorded while the voltage was off. High quality of BTO epitaxial films was confirmed by scanning transmission electron microscopy measurements …”

“…High‐quality BaTiO 3 (BTO) epitaxial films with a thickness of ≈2.8 nm were prepared on 0.7 wt% Nb‐doped SrTiO 3 (SNTO) substrates through pulse laser deposition (PLD). A high deposited oxygen pressure of 20 Pa was used to avoid the effect of oxygen vacancy migration on our electronic synapses . Using the standard lithography technique, Pt circular electrodes with a thickness of 100 nm were patterned on the BTO films (see the Experimental Section).…”

Controlled Sign Reversal of Electroresistance in Oxide Tunnel Junctions by Electrochemical-Ferroelectric Coupling

“…Typically, this approach relies on the use of narrow (100 ns) pulse sequences to switch ferroelectric polarization and avoid the drift of oxygen vacancies. Other authors have shown large hysteretic resistance changes in ferroelectric tunnel junctions resulting from the drift of oxygen vacancies [19,20]. Furthermore, samples produced with high intentional concentration of oxygen vacancies display reversed polarity (resistive) switching to the ferroelectric switching found in similar samples with low vacancy concentration [21].…”

Recent advances, perspectives, and challenges in ferroelectric synapses*

“…Various efforts such as strain [24] , electrode/barrier interface engineering [18,20] and functional electrode [17] have been introduced to increase the TER OFF/ON ratio in these oxide FTJs [25] . The TER OFF/ON ratio can be as large as 10 7 at room temperature [26] . In addition, using ferromagnetic metals as electrodes, enable a nonvolatile control of electronic and spintronic responses in multifunctional devices [27][28][29][30][31] .…”