Surface termination and stoichiometry of LaAlO3(001) surface studied by HRTEM

Sha, Haozhi; Liang, Shaoheng; Liu, Linhan; Cheng, Zhiqiang; Zhu, Jing; Yu, Rong

doi:10.1016/j.micron.2020.102919

Cited by 10 publications

(7 citation statements)

References 78 publications

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“…In contrast, transmission electron microscopy (TEM) is not subject to the aforementioned limitations of traditional surface science tools and offers a unique window to study the reduction of the oxide at an atomic scale from both the surface and subsurface regions at the same time. , Particularly, the recent developments in environmental TEM have enabled us to dynamically observe a gas–surface reaction under a gas-controlled environment . This was achieved by incorporating differential pumping local to the specimen, thereby allowing for the volume around the specimen to be filled with gases so that the pressure of the volume can be kept higher than that of the TEM column.…”

mentioning

confidence: 99%

Atomic Origin of the Autocatalytic Reduction of Monoclinic CuO in a Hydrogen Atmosphere

Sun

Zhu

et al. 2021

J. Phys. Chem. Lett.

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Reducibility is key for the use of bulk metal oxides in chemical transformations involving redox reactions, but probing microscopic processes of oxide reduction is challenging. This is because the insulating nature of bulk oxides restricts ion and electron spectroscopic measurements of oxide surfaces. Herein, using a combination of environmental transmission electron microscopy and atomistic modeling, we report direct in situ atomic-scale observations of the surface and subsurface dynamics and show that the hydrogen-induced CuO reduction occurs through the receding motion of Cu–O/Cu bilayer steps at the surface, the formation of the partially reduced CuO superstructure by the self-ordering of O vacancies in the subsurface, and the collapse of Cu–O layers in the bulk. All these substeps can be traced back to the progressively increased concentration and activity of O vacancies in the surface and subsurface of the oxide, thereby leading to the self-accelerated oxide reduction. These results demonstrate the microscopic details that may have a broader applicability in modulating various redox processes.

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confidence: 99%

Atomic Origin of the Autocatalytic Reduction of Monoclinic CuO in a Hydrogen Atmosphere

Sun

Zhu

et al. 2021

J. Phys. Chem. Lett.

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“…In fact, the previous first‐principle calculation showed that the formation energy of V La ‴ on LaO‐terminated surface is −0.5 eV whereas that of oxygen vacancy (V O ) is 6.0 eV, indicating the spontaneous formation of V La ‴. [ 33 ] While the formation of V O is not energetically favored at an uncompensated LaO‐terminated surface, we found that V O can also form at the charge‐compensated LaO‐terminated surface together with excess V La ‴ when the surface is annealed for a prolonged time in vacuum. The V La ‴ present in the surface LaO layer leads to the local relaxation of the interatomic spacing and even a surface symmetry when they are regularly ordered.…”

Section: Resultsmentioning

confidence: 99%

“…For the LaAlO 3 (001) polar surface, previous theoretical studies demonstrated that the surface reconstruction involves the formation and ordering of cation vacancies to compensate the surface charges. [31][32][33] Recently, the formation of (01n) vicinal surfaces with mixed termination has been proposed as an alternative to cancel the dipole moment normal to the LaAlO 3 (001) surface, rendering the surface nonpolar. [19] However, experimental verification that can explicitly address the role of charged vacancies and atomic steps in the high temperature surface reconstruction process of polar oxide surfaces has not yet been accomplished.…”

Section: Introductionmentioning

confidence: 99%

Direct Observation of Atomic Step‐Assisted Stabilization of Polar Surfaces

et al. 2023

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Polar surfaces are intrinsically unstable and thus highly reactive due to the uncompensated surface charges. The charge compensation is accompanied by various surface reconstructions, establishing novel functionality for their applications. The present in situ atomic‐scale electron microscopy study directly shows that the atomic step and step‐assisted reconstruction play central roles in the charge compensation of polar oxide surfaces. The flat (LaO)+‐terminated LaAlO3 (001) polar surface, when annealed at high temperature in vacuum, transits to the (015) vicinal surface via the dynamic motion and interaction of atomic steps. While the (015) vicinal surface possesses zero polarization along the surface normal, a thermodynamic ground state is achieved when the in‐plane polarization is fully compensated via the reconstruction of step‐edge atoms; the step‐edge La atoms are displaced from their ordinary atomic sites toward the adjacent Al step‐edge sites, resulting in the formation of negatively charged La vacancies at the corresponding step edges. As confirmed by first‐principles calculations, the observed step reconstruction of (015) vicinal surface can completely cancel both out‐of‐plane and in‐plane electric fields. This hitherto unknown mechanism reveals the central role of step reconstruction in stabilizing a polar surface, providing valuable insights for understanding the novel charge compensation mechanism accompanied by the step reconstruction.

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“…To compare the relative stability of the 1 Â 1 and 1 Â 1-Cu CUS structures, surface energies γ(T, P) were calculated using the methods in the study by Reuter, [13] which have been used in numerous studies. [5,[14][15][16][17][18] The surface energy can be written by…”

Section: Resultsmentioning

confidence: 99%

Atomic Structure of the Cu₂O(111) Surface: A Transmission Electron Microscopy and DFT + U Study

Xing

Meng

2021

Physica Status Solidi (b)

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The atomic structures of Cu 2 O surfaces can significantly affect catalytic properties. By combining aberration-corrected transmission electron microscopy (TEM) with density functional theory (DFT) calculations, it is shown that the Cu 2 O(111) surface stabilizes in a bulk-truncated 1 Â 1 structure with coordinatively unsaturated Cu atoms under low-oxygen conditions. This differs from the known 1 Â 1-Cu CUS structure with coordinatively unsaturated Cu atom vacancies.

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Surface termination and stoichiometry of LaAlO3(001) surface studied by HRTEM

Cited by 10 publications

References 78 publications

Atomic Origin of the Autocatalytic Reduction of Monoclinic CuO in a Hydrogen Atmosphere

Atomic Origin of the Autocatalytic Reduction of Monoclinic CuO in a Hydrogen Atmosphere

Direct Observation of Atomic Step‐Assisted Stabilization of Polar Surfaces

Atomic Structure of the Cu₂O(111) Surface: A Transmission Electron Microscopy and DFT + U Study

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Surface termination and stoichiometry of LaAlO3(001) surface studied by HRTEM

Cited by 10 publications

References 78 publications

Atomic Origin of the Autocatalytic Reduction of Monoclinic CuO in a Hydrogen Atmosphere

Atomic Origin of the Autocatalytic Reduction of Monoclinic CuO in a Hydrogen Atmosphere

Direct Observation of Atomic Step‐Assisted Stabilization of Polar Surfaces

Atomic Structure of the Cu2O(111) Surface: A Transmission Electron Microscopy and DFT + U Study

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Atomic Structure of the Cu₂O(111) Surface: A Transmission Electron Microscopy and DFT + U Study