Resistance switching behavior of atomic layer deposited SrTiO3 film through possible formation of Sr2Ti6O13 or Sr1Ti11O20 phases

Lee, Woongkyu; Yoo, Seong Yul; Yoon, Kyung Jean; Yeu, In Won; Chang, Hye Jung; Choi, Jung‐Hae; Hoffmann‐Eifert, Susanne; Waser, Rainer; Hwang, Cheol Seong

doi:10.1038/srep20550

Cited by 18 publications

(9 citation statements)

References 72 publications

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“…At this point it should be noted that, under reducing and oxidizing conditions at high temperatures, changes of the crystal geometry of the surface layer can be induced, due to modifications of the stoichiometry. This has been found by X-ray and TEM investigations showing the evolution of Magnéli phases or low Ti oxides of reduced TiO2 [53,116,117] and reduced SrTiO3 or BaTiO3 [118][119][120][121] or the creation of Ruddlesden Popper phases under oxidizing/reducing conditions, or after electrical polarization at room temperature [118,119,122]. Those effects can dramatically modify the height of the steps on the surface (see.…”

Section: Annihilations or Multiplications Of Dislocationsmentioning

confidence: 99%

“…The nature of electroformation and switching along nano-filaments in single crystals is still under discussion [29,[47][48][49][50][51][52][53][54][55]262,263]. One issue, which has not been dealt with in this chapter, is related to the possibility of a local transformation of the model binary and ternary oxides (here TiO 2 O 20 , [57,121,182,[264][265][266][267]) under electrical stimuli. Such solid-state transformations are most likely connected with extended defects.…”

Section: Role Of Dislocations In Resistive Switching Of Tio2 and Srtimentioning

confidence: 99%

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Influence of Dislocations in Transition Metal Oxides on Selected Physical and Chemical Properties

et al. 2018

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Studies on dislocations in prototypic binary and ternary oxides (here TiO 2 and SrTiO 3 ) using modern TEM and scanning probe microscopy (SPM) techniques, combined with classical etch pits methods, are reviewed. Our review focuses on the important role of dislocations in the insulator-to-metal transition and for redox processes, which can be preferentially induced along dislocations using chemical and electrical gradients. It is surprising that, independently of the growth techniques, the density of dislocations in the surface layers of both prototypical oxides is high (10 9 /cm 2 for epipolished surfaces and up to 10 12 /cm 2 for the rough surface). The TEM and locally-conducting atomic force microscopy (LCAFM) measurements show that the dislocations create a network with the character of a hierarchical tree. The distribution of the dislocations in the plane of the surface is, in principle, inhomogeneous, namely a strong tendency for the bundling and creation of arrays or bands in the crystallographic <100> and <110> directions can be observed. The analysis of the core of dislocations using scanning transmission electron microscopy (STEM) techniques (such as EDX with atomic resolution, electron-energy loss spectroscopy (EELS)) shows unequivocally that the core of dislocations possesses a different crystallographic structure, electronic structure and chemical composition relative to the matrix. Because the Burgers vector of dislocations is per se invariant, the network of dislocations (with additional d 1 electrons) causes an electrical short-circuit of the matrix. This behavior is confirmed by LCAFM measurements for the stoichiometric crystals, moreover a similar dominant role of dislocations in channeling of the current after thermal reduction of the crystals or during resistive switching can be observed. In our opinion, the easy transformation of the chemical composition of the surface layers of both model oxides should be associated with the high concentration of extended defects in this region. Another important insight for the analysis of the physical properties in real oxide crystals (matrix + dislocations) comes from the studies of the nucleation of dislocations via in situ STEM indentation, namely that the dislocations can be simply nucleated under mechanical stimulus and can be easily moved at room temperature.

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Section: Annihilations or Multiplications Of Dislocationsmentioning

confidence: 99%

Section: Role Of Dislocations In Resistive Switching Of Tio2 and Srtimentioning

confidence: 99%

Influence of Dislocations in Transition Metal Oxides on Selected Physical and Chemical Properties

et al. 2018

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“…In previous studies, different microscopy techniques, including scanning tunneling microscopy, , local conduction atomic force microscopy, X-ray absorption spectroscopy (XAS), − and transmission electron microscopy (TEM), − have been applied to study the conducting filaments and to obtain a better understanding of their structural nature. In particular for ECM materials (i.e., SiO 2 ), TEM has shown the capability to reveal the structural details of the ECM mechanism. , For the best-known prototype VC material SrTiO 3 , XAS has been demonstrated to be a successful technique to explore the Ti valence change and O-vacancies. − Nevertheless, by means of XAS it is hardly possible to visualize the local structural details of individual filaments on the atomic scale due to the limit of the lateral resolution of the technique (≥25 nm).…”

mentioning

confidence: 99%

“…SrTiO 3 model systems, i.e., epitaxial structures, , bicrystals, − and engineered dislocations, are currently under intense investigation in order to understand the fundamental mechanism of resistive switching. Extended defects, such as one-dimensional dislocations ,, and two-dimensional stacking faults, , as well as secondary oxygen deficient phases, e.g., Sr 2 Ti 6 O 13 /SrTi 11 O 20 in polycrystalline films, have been associated with the conducting filaments. The defects essential to the conducting filament formation and disruption are still under debate.…”

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confidence: 99%

Nanosized Conducting Filaments Formed by Atomic-Scale Defects in Redox-Based Resistive Switching Memories

Jia

Koehl

et al. 2017

Chem. Mater.

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Redox-based resistive switching phenomena are found in many metal oxides and hold great promise for applications in next-generation memories and neuromorphic computing systems. Resistive switching involves the formation and disruption of electrically conducting filaments through ion migration accompanied by local electrochemical redox reactions. These structural changes are often explained by point defects, but so far clear experimental evidence of such defects is missing. Here, nanosized conducting filaments in Fe-doped SrTiO3 thin-film memories are visualized, for the first time, by scanning transmission electron microscopy and core-loss spectroscopy. Conducting filaments are identified by a high local concentration of trivalent titanium ions correlating to oxygen vacancies. Strontium vacancies and lattice distortions also exist in the filaments. Despite a high concentration of defects in the filaments, their general SrTiO3 perovskite structure is essentially preserved. First insights into the switching mechanism are deduced from a snapshot simultaneously showing multiple nanosized filaments in different evolutionary stages. The coexistence of a high Ti3+ concentration along with Sr- and O-vacancies in the conducting filaments provides atomic scale explanations for the resistive switching mechanisms. The results shed unique light on the complexity of the conducting filament formation that cation and anion defects need to be considered jointly.

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“…For the investigation of the performance of ternary metal oxides, strontium titanate (SrTiO 3 ) has become a prototype material due to the possibility of controlling its resistance between insulating, metallic and even superconducting behaviour related to a self-doping effect by oxygen vacancies 2 – 5 . While oxides with perovskite structure are regarded as very stable materials since many of them can be found in rocks, it has been shown recently that resistive switching is related to a local decomposition and phase transformation by an electroforming process resulting in the evolution of switchable nanofilamentary structures 6 , 7 . As the main driving force of this transformation, the movement of oxygen vacancies upon application of an electric field has been identified.…”

Section: Introductionmentioning

confidence: 99%

Electrically controlled transformation of memristive titanates into mesoporous titanium oxides via incongruent sublimation

Rodenbücher

Meuffels

Bihlmayer

et al. 2018

Sci Rep

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Perovskites such as SrTiO3, BaTiO3, and CaTiO3 have become key materials for future energy-efficient memristive data storage and logic applications due to their ability to switch their resistance reversibly upon application of an external voltage. This resistance switching effect is based on the evolution of nanoscale conducting filaments with different stoichiometry and structure than the original oxide. In order to design and optimize memristive devices, a fundamental understanding of the interaction between electrochemical stress, stoichiometry changes and phase transformations is needed. Here, we follow the approach of investigating these effects in a macroscopic model system. We show that by applying a DC voltage under reducing conditions on a perovskite slab it is possible to induce stoichiometry polarization allowing for a controlled decomposition related to incongruent sublimation of the alkaline earth metal starting in the surface region. This way, self-formed mesoporous layers can be generated which are fully depleted by Sr (or Ba, Ca) but consist of titanium oxides including TiO and Ti3O with tens of micrometre thickness. This illustrates that phase transformations can be induced easily by electrochemical driving forces.

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Resistance switching behavior of atomic layer deposited SrTiO3 film through possible formation of Sr2Ti6O13 or Sr1Ti11O20 phases

Cited by 18 publications

References 72 publications

Influence of Dislocations in Transition Metal Oxides on Selected Physical and Chemical Properties

Influence of Dislocations in Transition Metal Oxides on Selected Physical and Chemical Properties

Nanosized Conducting Filaments Formed by Atomic-Scale Defects in Redox-Based Resistive Switching Memories

Electrically controlled transformation of memristive titanates into mesoporous titanium oxides via incongruent sublimation

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