Atomic-resolution imaging of electrically induced oxygen vacancy migration and phase transformation in SrCoO2.5-σ

Zhang, Qinghua; He, Xu; Shi, Jinan; Lu, Nianduan; Li, Haobo; Yu, Qian; Zhang, Ze; Chen, Lei; Morris, Bill; Xu, Qiang; Yu, Pu; Gu, Lin; Jin, Kuijuan; Nan, Ce Wen

doi:10.1038/s41467-017-00121-6

Cited by 74 publications

(83 citation statements)

References 27 publications

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“…Moreover, the O K ‐edge of XAS shows that the Co–O peak hybridization intensity of PV‐SCO is stronger than BM‐SCO. Similar results can be obtained from the EELS measurements (Figure S3, Supporting Information) . The electrical transport properties of BM‐SCO and PV‐SCO were measured to explore the resistivity change during the phase transformation process.…”

Section: Resultssupporting

confidence: 75%

“…The brownmillerite SrCoO 2.5 (BM‐SCO) structure, which consists of alternating stacks of [CoO 4 ]‐tetrahedral and [CoO 6 ]‐octahedron layers with ordered oxygen vacancy channels in the [110] crystal direction, provides a model system for oxygen ion insertion and extraction . Besides, the cobalt ions are multivalent such as the stable Co 2+ or Co 3+ and the active Co 4+ , providing the possibility of reversible redox reaction for SCO .…”

Section: Introductionmentioning

confidence: 99%

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Electrolyte‐Gated Synaptic Transistor with Oxygen Ions

Huang

Chen

Zhang

et al. 2019

Adv Funct Materials

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118

101

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Artificial synaptic devices are the essential hardware of neuromorphic computing systems, which can simultaneously perform signal processing and information storage between two neighboring artificial neurons. Emerging electrolyte-gated transistors have attracted much attention for efficient synaptic emulation by using an addition gate terminal. Here, an electrolyte-gated synaptic device based on the SrCoO x (SCO) films is proposed. It is demonstrated that the reversible modulation of SCO phase transforms the brownmillerite SrCoO 2.5 and perovskite SrCoO 3−δ , through controlling the insertion and extraction of oxygen ions with electrolyte gating. Nonvolatile multilevel conduction states can be realized in the SCO films following this route. The synaptic functions such as the long-term potentiation and depression of synaptic weight, spike-timing-dependent plasticity, as well as spiking logic operations in the device are successfully mimicked. These results provide an alternative avenue for future neuromorphic devices via electrolyte-gated transistors with oxygen ions.

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Section: Resultssupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Electrolyte‐Gated Synaptic Transistor with Oxygen Ions

Huang

Chen

Zhang

et al. 2019

Adv Funct Materials

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118

101

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“…For example, brownmillerite SrCoO 2.5 (SCO) can undergo polymorphic phase transition under electric field control and has resistive switching behavior. 5,[7][8][9][10] Brownmillerite SrFeO x (SFO) with similar structure of SCO has been extensively studied due to its promising application in the fields of electrodes of fuel cell, magnetic storage, redox reaction catalyst, [11][12][13][14][15] etc. In addition, partial substitutions of the B specie of ABO 2.5 produce complex brownmillerite oxides such as Ca 2 FeAlO 5 , Ca 2 FeCoO 5 , etc.…”

Section: Introductionmentioning

confidence: 99%

Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective

Tao

Zhang

et al. 2019

J Am Ceram Soc

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Brownmillerite‐type oxides are a large family of structural and functional materials that are of great concern. In this study, the occupancy mechanism of Fe and Al ions in brownmillerite Ca2FeAlO5 is revealed and the specific configuration of Ca2FeAlO5 is proposed for the first time. Through the energy analysis of a series of conjectured models based on well‐defined ab initio calculations, we find that the distribution of Al and Fe in Ca2FeAlO5 follows the “homogeneous layer principle”, namely, Al and Fe tend to form homogeneous octahedral layers or tetrahedral chains rather than mixed layers or chains of two elements along the b axis. The theoretical Ca2FeAlO5 structure with specific atomic occupancy is proposed based on energy analysis and previous experiments, which is of fundamental significance for further study of its physical and chemical properties. Moreover, the influence of entropy increment on the stability of Ca2FeAlO5 crystal is clarified, which paves the way to investigate the structures and properties of Ca2FeAlO5 and other brownmillerite members.

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“…For example, oxygen‐deficient SrTiO 3− x becomes conductive, in contrary stoichiometric SrTiO 3 (STO) is a typical band insulator with a band gap of 3.2 eV. In manganite‐, cobalt‐, iron‐, and nickel‐based perovskites, the nonstoichiometry of oxygen not only introduces electron/hole doping but also affects the super‐exchange or double‐exchange interactions by modification of the metal–oxygen bond length and/or angle . One example is oxygen‐deficient LaCoO 3− x which becomes a ferromagnetic (FM) insulator via modification of Co spin states, while stoichiometric LaCoO 3 is antiferromagnetic (AFM).…”

mentioning

confidence: 99%

Controlling the Magnetic Properties of LaMnO₃/SrTiO₃ Heterostructures by Stoichiometry and Electronic Reconstruction: Atomic‐Scale Evidence

Tang

Paudel

et al. 2019

Advanced Materials

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Charges and spins in strongly correlated systems determine the electronic and magnetic structures, which define the cor responding electronic and magnetic pro perties. [1,2] Charge modulation, achieved through chemical and electrostatic doping, is a common technique to modify the band filling status. These modified elec tronic structures have an influence on the properties, e.g. high temperature super conductivity, electronic phase separation, and charge ordering. [2][3][4] Nonstoichiom etry, which commonly exists in materials, results in an unintentional doping, altering their properties. [5] For example, oxygen deficient SrTiO 3−x becomes conductive, [6] in contrary stoichiometric SrTiO 3 (STO) is a typical band insulator with a band gap of 3.2 eV. In manganite, [7,8] cobalt, [9,10] iron, and nickelbased perovskites, [11,12] the nonstoichiometry of oxygen not only introduces electron/hole doping but also affects the superexchange or double exchange interactions by modification of Interface-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking are of importance for fundamental physics and device applications. How interfaces affect the interplay between charge, spin, orbital, and lattice degrees of freedom is the key to boosting device performance. In LaMnO 3 /SrTiO 3 (LMO/STO) polar-nonpolar heterostructures, electronic reconstruction leads to an antiferromagnetic to ferromagnetic transition, making them viable for spin filter applications. The interfacial electronic structure plays a critical role in the understanding of the microscopic origins of the observed magnetic phase transition, from antiferromagnetic at 5 unit cells (ucs) of LMO or below to ferromagnetic at 6 ucs or above, yet such a study is missing. Here, an atomic scale understanding of LMO/STO ambipolar ferromagnetism is offered by quantifying the interface charge distribution and performing first-principles density functional theory (DFT) calculations across this abrupt magnetic transition. It is found that the electronic reconstruction is confined within the first 3 ucs of LMO from the interface, and more importantly, it is robust against oxygen nonstoichiometry. When restoring stoichiometry, an enhanced ferromagnetic insulating state in LMO films with a thickness as thin as 2 nm (5 uc) is achieved, making LMO readily applicable as barriers in spin filters. Ambipolar FerromagnetismThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

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Atomic-resolution imaging of electrically induced oxygen vacancy migration and phase transformation in SrCoO2.5-σ

Cited by 74 publications

References 27 publications

Electrolyte‐Gated Synaptic Transistor with Oxygen Ions

Electrolyte‐Gated Synaptic Transistor with Oxygen Ions

Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective

Controlling the Magnetic Properties of LaMnO₃/SrTiO₃ Heterostructures by Stoichiometry and Electronic Reconstruction: Atomic‐Scale Evidence

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Atomic-resolution imaging of electrically induced oxygen vacancy migration and phase transformation in SrCoO2.5-σ

Cited by 74 publications

References 27 publications

Electrolyte‐Gated Synaptic Transistor with Oxygen Ions

Electrolyte‐Gated Synaptic Transistor with Oxygen Ions

Atomic occupancy mechanism in brownmillerite Ca2FeAlO5 from a thermodynamic perspective

Controlling the Magnetic Properties of LaMnO3/SrTiO3 Heterostructures by Stoichiometry and Electronic Reconstruction: Atomic‐Scale Evidence

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Atomic occupancy mechanism in brownmillerite Ca₂FeAlO₅ from a thermodynamic perspective

Controlling the Magnetic Properties of LaMnO₃/SrTiO₃ Heterostructures by Stoichiometry and Electronic Reconstruction: Atomic‐Scale Evidence