Homogeneity and variation of donor doping in Verneuil-grown SrTiO3:Nb single crystals

Rodenbücher, Christian; Luysberg, M.; Schwedt, Alexander; Havel, Viktor; Gunkel, Felix; Mayer, Joachim; Waser, Rainer

doi:10.1038/srep32250

Cited by 29 publications

(30 citation statements)

References 38 publications

(58 reference statements)

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“…On the one hand, we know that the bulk of the Nb:SrTiO3 crystals possess a homogenous distribution of aliovalent Nb ions and, without doubt, the dislocations play only a minor role for the global metallic conductivity of the matrix induced by such chemical doping, as presented by Rodenbücher et al [246]. On the other hand, in situ and in operando investigations using surface sensitive techniques of the surface layer of Nb:SrTiO3 [227] give evidence that the stoichiometry of Ti and Sr can dramatically change and the typical so-called metallic pick at the bottom of the conducting band actually disappears, which in turn "switches" the electrical properties of the surface region to become semiconducting in character.…”

Section: Electrical Properties Of the Dislocations In Tio 2 And Srtiomentioning

confidence: 99%

“…Here, examples of the current (resistance) mapping of SrTiO 3 and TiO 2 are given in Figures 35 and 36, respectively. It should also be noticed that TEM images of SrTiO 3 :Nb give a rather homogeneous picture of the samples [246], while LCAFM measurements indicate spatial fluctuations of the conductivity at the surface [227]. layer.…”

Section: Electrical Properties Of the Dislocations In Tio 2 And Srtiomentioning

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: Electrical Properties Of the Dislocations In Tio 2 And Srtiomentioning

confidence: 99%

Section: Electrical Properties Of the Dislocations In Tio 2 And Srtiomentioning

confidence: 99%

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

et al. 2018

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“…For oxide‐based perovskites, the required temperatures for single‐crystal synthesis typically exceed 1000 °C. Examples include the Verneuil‐ or ‘flame fusion’ technique for Nb‐doped SrTiO 3 and the Czochralski method (the industry standard for producing silicon wafers) for GdGaO 3 and NdAlO 3 . The floating‐zone method is reported for LaMnO 3 and SrRuO 3 and also for the layered perovskite La 1− x Sr 1+ x MnO 4 , an n = 1 member of the RP structural series .…”

Section: Preparation Methods For Perovskitesmentioning

confidence: 99%

From colossal magnetoresistance to solar cells: An overview on 66 years of research into perovskites

Wagner

Wackers

Cardinaletti

et al. 2017

Phys. Status Solidi A

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Perovskites are a huge family of compounds to which the natural titanium mineral CaTiO 3 is the common ancestor. The cubic structure looks apparently simple, but the variety of metal ions and mixtures thereof that fit into a perovskite lattice is tremendous. Even in the case that the ionic radii do not allow for a perfect cubic ordering, there are various superstructures and orbital-ordering effects to cope elegantly with distortions. The compositional and structural flexibility offers a large toolbox to design and synthesize perovskites with tailored properties searched for by physicists, chemists, materials scientists and device engineers. These materials are equally of interest for fundamental studies and for applied research while both viewpoints cross-fertilize each other regularly. Our overview starts with the discovery of ferromagnetism in manganites in 1950 and ranges until 2016: Today, halide perovskites are fully in focus for their potential in photovoltaic applications. This is certainly not an endpoint, but another milestone in a long series of often-unexpected discoveries on an 'evergreen material'.Ball-and-stick model of the ideal cubic perovskite structure. The cation at the central position or 'B site' (small black dot) defines the group name (e.g., titanates) and plays a key role for the physical properties of the material.

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“…Although high-quality single crystals of SrTi 1-x Nb x O 3 species with x > 0.1 are not available due to the low solubility limit of Nb in the lattice [16], epitaxial films with these material compositions can be fabricated by PLD [17]. As summarized in Fig.…”

Section: Pulsed Laser Depositionmentioning

confidence: 99%

“…10. 16 Schematic illustration of CAN (calcium aluminate with nanopore) gated functional oxide thin-film transistor with a three-terminal electrodes geometry. Since 30 volume percent of the CAN film is occupied with liquid water, H + and OH − ions in the CAN film move with a gate voltage application.…”

Section: Utilizing Antiferromagnetic Insulator/ferromagneticmentioning

confidence: 99%

Fabrication, Characterization, and Modulation of Functional Nanolayers

Ohta

Hiramatsu

2018

Nanoinformatics

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Regions of a few nanometers at the surface or interface of a material exhibit various functional properties, which differ from those of the bulk because the electrons and/or ions receive different potentials due to the incoherent atomic arrangement. High-quality epitaxial films of functional materials called "nanolayers" are important to utilize such functional properties. However, fabrication of high-quality nanolayers of complex materials with complicated crystal structures is usually challenging due to the difference in the thermochemical properties of the constituents. In this chapter, epitaxial growth techniques, especially "reactive solid-phase epitaxy" of functional oxides and chalcogenides, are reviewed based on the authors' efforts. Additionally, this chapter reviews several modulation methods of optical, electrical, and magnetic properties of functional oxide nanolayers.

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Homogeneity and variation of donor doping in Verneuil-grown SrTiO3:Nb single crystals

Cited by 29 publications

References 38 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

From colossal magnetoresistance to solar cells: An overview on 66 years of research into perovskites

Fabrication, Characterization, and Modulation of Functional Nanolayers

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