Brownmillerite thin films as fast ion conductors for ultimate-performance resistance switching memory

Abstract

An oxide-based resistance memory is a leading candidate to replace Si-based flash memory as it meets the emerging specifications for future memory devices. The non-uniformity in the key switching parameters and low endurance in conventional resistance memory devices are preventing its practical application. Here, a novel strategy to overcome the aforementioned challenges has been unveiled by tuning the growth direction of epitaxial brownmillerite SrFeO thin films along the SrTiO [111] direction so that the oxygen vacancy channels can connect both the top and bottom electrodes rather directly. The controlled oxygen vacancy channels help reduce the randomness of the conducting filament (CF). The resulting device displayed high endurance over 10 cycles, and a short switching time of ∼10 ns. In addition, the device showed very high uniformity in the key switching parameters for device-to-device and within a device. This work demonstrates a feasible example for improving the nanoscale device performance by controlling the atomic structure of a functional oxide layer.

Effects of the Heterointerface on the Growth Characteristics of a Brownmillerite SrFeO2.5 Thin Film Grown on SrRuO3 and SrTiO3 Perovskites

“…2.5 J cm −2 ) and then the 60-70-nm-thick SFO layer was deposited on top of the SRO layer. Details of the thin film fabrication are reported elsewhere 23,25 .…”

“…The oxygen vacancy channels are believed to form a pathway for easy and rapid oxygen-ion transport and to contribute to the ionic conductivity of the compound in applications such as solid-oxide fuel cells and resistive-switching memory devices [20][21][22] . The highly anisotropic structure originating from the ordered oxygen vacancy channels of the BM structure could alter the growth behaviour 21,23 . Many studies have exploited epitaxial strain to manipulate the growth orientation of BM thin films.…”

Atomic occupancy mechanism in brownmillerite Ca2FeAlO5 from a thermodynamic perspective

“…Brownmillerite oxides are a large family of versatile structural and functional materials that can be derived from the perovskite structures. The perovskite structure is generally expressed as ABO 3‐ δ , where δ ≈ 0, A is the rare or alkaline earth metal and B is the transition metal.…”

Optimization of the multi-mem response of topotactic redox La$_{1/2}$Sr$_{1/2}$Mn$_{1/2}$Co$_{1/2}$O$_{3-x}$

“…Upon consecutive electrical cycling, any of these reduced states can be stabilized and, therefore, the corresponding resistance state presents a significant dispersion, affecting the device reliability. A more stable memristive response was shown for perovskites such as SrCoO 3 [14][15][16][17], SrFeO 3 [18][19][20] or La 2/3 Sr 1/3 MnO 3 [21], which are able to reversibly switch to/from a brownmillerite-like (strongly reduced) phase and are examples of the so-called topotactic redox materials. For these materials, it is possible to reversibly switch between two phases with different structure and a large difference in oxygen content (and resistivity).…”

“…For these materials, it is possible to reversibly switch between two phases with different structure and a large difference in oxygen content (and resistivity). As both oxidized and reduced states are linked to an energy landscape with well defined minima, the electrical switching between both phases is more reproducible and controlled [14,17]. An important issue in topotactic redox materials-based memristors is the significant oxygen exchange between the device and the atmosphere -usually neglected in memristive perovskites [12,13]-, related to the large difference in oxygen content between oxidized and reduced phases.…”