Subtleties in ADF imaging and spatially resolved EELS: A case study of low-angle twist boundaries in SrTiO3

Fitting, Lena; Thiel, Stefan; Schmehl, A.; Mannhart, J.; Muller, David A.

doi:10.1016/j.ultramic.2006.04.019

Cited by 73 publications

(62 citation statements)

References 17 publications

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“…The shape of the L 2;3 edge [10], the chemical shift [11,12] and the L 3 =L 2 ratio [13] have all been used as a fingerprint for the transition metal valence. In fact, the correlation between the energy-loss near-edge structure (ELNES) and valence in different transition metal oxides was confirmed by several experiments in literature [10,[14][15][16][17][18][19][20][21]. The higher the energy resolution, the more convincing this link between valence and ELNES features becomes.…”

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confidence: 62%

2D Atomic Mapping of Oxidation States in Transition Metal Oxides by Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy

et al. 2011

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Using a combination of high-angle annular dark-field scanning transmission electron microscopy and atomically resolved electron energy-loss spectroscopy in an aberration-corrected transmission electron microscope we demonstrate the possibility of 2D atom by atom valence mapping in the mixed valence compound Mn 3 O 4 . The Mn L 2;3 energy-loss near-edge structures from Mn 2þ and Mn 3þ cation sites are similar to those of MnO and Mn 2 O 3 references. Comparison with simulations shows that even though a local interpretation is valid here, intermixing of the inelastic signal plays a significant role. This type of experiment should be applicable to challenging topics in materials science, such as the investigation of charge ordering or single atom column oxidation states in, e.g., dislocations. DOI: 10.1103/PhysRevLett.107.107602 PACS numbers: 79.20.Uv, 68.37.Ma, 75.25.Dk In transition metal oxides, the oxidation state of the transition metal cations is of fundamental importance as the physical properties of many oxides are determined by the occupancy of the cation d bands. Multiferroicity, for example, can be driven by charge ordering of these cations, as in Fe 3 O 4 and Pr 1Àx Ca x MnO 3 [1-3]. However, the exact mechanism of multiferroic behavior is not fully understood to date. A method allowing for direct mapping of cation valence states in these materials at atomic resolution should therefore provide further insight into the origin of multiferroicity.Recently, atomic resolution elemental mapping has become feasible by means of spatially resolved electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy in a scanning transmission electron microscope (STEM-EELS and STEM-EDX) [4][5][6][7][8][9]. At the same time, tremendous effort is being invested into the identification of the oxidation states of cations using electron energy-loss spectroscopy (EELS). The shape of the L 2;3 edge [10], the chemical shift [11,12] and the L 3 =L 2 ratio [13] have all been used as a fingerprint for the transition metal valence. In fact, the correlation between the energy-loss near-edge structure (ELNES) and valence in different transition metal oxides was confirmed by several experiments in literature [10,[14][15][16][17][18][19][20][21]. The higher the energy resolution, the more convincing this link between valence and ELNES features becomes. Combining the atomic resolution capabilities of a STEM with bonding and valence information from EELS is a highly attractive prospect. While bonding information has been obtained at atomic resolution [7,17,22], 2D oxidation state mapping at the atomic level in, e.g., metaloxide materials has remained challenging due to poor EELS signal-to-noise ratio and the need for simultaneous high spatial and energy resolution of the instrument [10,17,23].Mn 3 O 4 is known to be a mixed valence compound, containing both Mn 2þ and Mn 3þ ions at room temperature [24]. It has a spinel structure with lattice parameters a ¼ 5:762 A and c ¼ 9:4696 A and space group I41=amd. Many interesting...

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confidence: 62%

2D Atomic Mapping of Oxidation States in Transition Metal Oxides by Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy

et al. 2011

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“…1b; see the guiding A and B circles, Fig. 1b-f) demonstrates that atomic resolution was systematically obtained in each map, unprecedented for the spatially resolved investigations of dislocations [17][18][19][20][21][22][23][24] . Intriguingly, the Mn-Ti interdiffusion shows a radial pattern centred at the dislocation (see the dashed arcs, Fig.…”

Section: Resultsmentioning

confidence: 89%

“…In Fig. 1a (inset), the low-angle ADF (LAADF) imaging, a classical approach for revealing dislocation-strain contrasts 5,19 , resolves the characteristic strain field of the dislocations (arrows). The close HAADF inspection of an individual dislocation ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Condensation of two-dimensional oxide-interfacial charges into one-dimensional electron chains by the misfit-dislocation strain field

et al. 2014

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The success of semiconductor technology is largely ascribed to controlled impacts of strains and defects on the two-dimensional interfacial charges. Interfacial charges also appear in oxide heterojunctions such as LaAlO 3 /SrTiO 3 and (Nd 0.35 Sr 0.65 )MnO 3 /SrTiO 3 . How the localized strain field of one-dimensional misfit dislocations, defects resulting from the intrinsic misfit strains, would affect the extended oxide-interfacial charges is intriguing and remains unresolved. Here we show the atomic-scale observation of one-dimensional electron chains formed in (Nd 0.35 Sr 0.65 )MnO 3 /SrTiO 3 by the condensation of characteristic twodimensional interfacial charges into the strain field of periodically arrayed misfit dislocations, using chemical mapping and quantification by scanning transmission electron microscopy. The strain-relaxed inter-dislocation regions are readily charge depleted, otherwise decorated by the pristine charges, and the corresponding total-energy calculations unravel the undocumented charge-reservoir role played by the dislocation-strain field. This two-dimensionalto-one-dimensional electronic condensation represents a novel electronic-inhomogeneity mechanism at oxide interfaces and could stimulate further studies of one-dimensional electron density in oxide heterostructures.

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“…While the first operation would leave the length of the c-axis unaltered, the latter would even shrink it resulting in a strong contraction of the unit cell volume. Figure 1D shows the strain pattern associated with the misfit dislocation structure of a 7.1 nm thick film projected on the interface plane, using annular dark field scanning transmission electron microscopy at low beam convergence angles (Fitting et al, 2006). The density of the pattern can be manipulated through the thickness of the film.…”

Section: Misfit Strainmentioning

confidence: 99%

Interfaces and Nanostructures of Functional Oxide Octahedral Framework Structures

Sandiumenge¹,

Bagués²,

Santiso³

2014

Front. Mater.

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In the past decade, the rich physics exhibited by solid interfaces combining octahedral framework structures of transition-metal oxides has fascinated the materials science community. However, their behavior still eludes the current understanding of classical semiconductor and metal epitaxy. The reason for that is rooted in the surprising versatility of linked coordination units to adapt to a dissimilar substrate and the strong sensitivity of strongly correlated electron oxides to external perturbations. The confluence of atomic control in oxide thin film epitaxy, state of the art high spatial resolution characterization techniques, and electronic-structure computations, has allowed in recent years to obtain first insights on the microscopic mechanisms governing the epitaxy of these complex materials.

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Subtleties in ADF imaging and spatially resolved EELS: A case study of low-angle twist boundaries in SrTiO3

Cited by 73 publications

References 17 publications

2D Atomic Mapping of Oxidation States in Transition Metal Oxides by Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy

2D Atomic Mapping of Oxidation States in Transition Metal Oxides by Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy

Condensation of two-dimensional oxide-interfacial charges into one-dimensional electron chains by the misfit-dislocation strain field

Interfaces and Nanostructures of Functional Oxide Octahedral Framework Structures

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