Predicting the Onset of Metal–Insulator Transitions in Transition Metal Oxides—A First Step in Designing Neuromorphic Devices

Abstract

Several transition metal oxides, including La1–x Sr x CoO3, are promising materials to realize resistive switching devices for neuromorphic applications, as they can undergo a metal-to-insulator transition (MIT) upon small perturbations to their electronic structure. Here, we focus on the MIT induced by varying the oxygen vacancy concentration, and we propose a model to predict the required electrical bias, based on three fundamental quantities: the vacancy formation energy, the permanent polarization in the material, and its dielectric constant. We obtain these quantities using first-principles electronic structure calculations, and we discuss strategies to minimize the electrical bias which may be adopted experimentally to design and optimize neuromorphic devices.

Doping- and Strain-Dependent Electrolyte-Gate-Induced Perovskite to Brownmillerite Transformation in Epitaxial La1–xSrxCoO3−δ Films

“…V th drops from at least 2.4 to 3.0 V at x = 0 (where the upward arrow indicates that long-range BM order was not detected in SXRD) to negligible at x = 0.70. Below, we discuss specific conclusions regarding the origin of the overall decrease in V th with x and its apparent nonmonotonicity in Figure ; for now, we note only that V th is clearly doping-tunable, a feature that would appear attractive for applications such as neuromorphic computing. ,− ,− …”

Control of Oxygen Vacancy Ordering in Brownmillerite Thin Films via Ionic Liquid Gating

“… 1 − 5 The phase transformation between brownmillerite and perovskite is enabled by applying an electric-field even at room temperature owing to the low oxygen vacancy formation energy and the high oxygen vacancy diffusivity of such systems. 24 , 25…”

Quantum materials for energy-efficient neuromorphic computing

“…Examples include: controlling oxygen vacancies in vanadates, 44 doping rare-earth nickelates (e.g., SmNiO 3 ) with light ions such as hydrogen, 45 and controlling vacancies and doping in LaCoO 3 . 46 Due to their high mobility, the distribution of light ions or ion vacancies is sensitive to short voltage pulses, enabling controllable tuning of neuromorphic device resistance. Memory nano-devices based on this effect are promising candidates for artificial neuromorphic synapses.…”

“…Zhang and Galli recently elucidated the impact of oxygen vacancies on the structural, electronic, and magnetic changes responsible for the metal-insulator transition in cobaltites. 46 Interestingly, they showed that cooperative structural distortions, rather than local bonding changes, are responsible for the gap closing.…”