Atomic geometry of steps on metal-oxide single crystals

Henrich, Victor E.; Shaikhutdinov, Shamil K.

doi:10.1016/j.susc.2004.10.047

Cited by 23 publications

(15 citation statements)

References 15 publications

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“…A higher coordinative unsaturation in a metal oxide surface causes the instability of the step edge. 31,34) A similar discussion can be seen for the Si surface in which the number of dangling bonds is the key factor. The step edge with the lowest number of dangling bonds is reported as the thermodynamically most stable step edge in the Si(111) surface.…”

Section: Resultssupporting

confidence: 59%

Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO₂(111) with Changing Annealing Condition

Shahed

Sainoo

Komeda

2011

Jpn. J. Appl. Phys.

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The surface morphology variation of CeO 2 (111) with changing annealing condition was examined by scanning tunneling microscopy (STM). Hexagonal islands and pits containing two types of step edge have been found as characteristic features in a short-time-annealed surface. We observed that the triangular pits having only one type of step edge increase in number with annealing time, while the hexagonal pits and islands decrease and the deviated hexagonal pits increase.Step edges of the hexagonal pits that have higher coordinative saturation get preferential thermodynamic stability to form triangular pits, the most stable surface structures on the CeO 2 (111) surface in the equilibrium stage of annealing. These results have important implications for controlling catalytic activity on ceria. #

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Section: Resultssupporting

confidence: 59%

Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO₂(111) with Changing Annealing Condition

Shahed

Sainoo

Komeda

2011

Jpn. J. Appl. Phys.

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“…Note that the longer steps (termed A*-1 in ref. [267], shown in Figure 46(c)) are not equivalent to the shorter ones (B-1, shown in Figure (d)). The longer steps terminate at surface Fe tet atoms (grey), while the shorter steps terminate at the Fe oct atoms (red).…”

Section: 44mentioning

confidence: 91%

“…Wang et al [266] summarized the various possibilities for the structure of each step on the basis that any Fe atom missing more than half of its O ligands should not be stable at a step edge. They then compared the different possibilities in terms of the number of dangling bonds and the excess charge, and found that the two methods predict a different stability hierarchy, in contrast to similar work on Fe 3 O 4 (111) [267]. Noting that the surface Fe atoms are now known to possess charges different to the bulk, it perhaps makes more sense to consider the predictions based on coordinative unsaturation.…”

Section: Step Edgesmentioning

confidence: 99%

Iron oxide surfaces

Parkinson

2016

Surface Science Reports

501

463

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The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), hematite (α-Fe 2 O 3 ), and wüstite (Fe 1-x O) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe 3 O 4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment, and because it is an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed.The best understood iron oxide surface at present is probably Fe 3 O 4 (100); the structure is known with a high degree of precision and the major defects and properties are well characterised. A major factor in this is that a termination at the Fe oct -O plane can be reproducibly prepared by a variety of methods, as long as the surface is annealed in 10 Such straightforward preparation of a monophase termination is generally not the case for other iron oxide surfaces. All available evidence suggests the oft-studied (√2×√2)R45° reconstruction results from a rearrangement of the cation lattice in the outermost unit cell in which two octahedral cations are replaced by one tetrahedral interstitial, a motif conceptually similar to well-known Koch-Cohen defects in Fe (0001) is the most studied hematite surface, but 2 difficulties preparing stoichiometric surfaces under UHV conditions have hampered a definitive determination of the structure. There is evidence for at least three terminations: a bulk-like termination at the oxygen plane, a termination with half of the cation layer, and a termination with ferryl groups. When the surface is reduced the so-called "bi-phase" structure is formed, which eventually transforms to a Fe 3 O 4 (111)-like termination. The structure of the bi-phase surface is controversial; a largely accepted model of coexisting Fe 1-x O and α-Fe 2 O 3 (0001) islands was recently challenged and a new structure based on a thin film of Fe 3 O 4 (111) on α-Fe 2 O 3 (0001) was proposed. The merits of the compet...

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“…Let us mention, e.g. the recent work on vicinal oxide surfaces performed for SrTiO 3 [93] and Fe 3 O 4 [94] and the DFT investigation of Si(114)-(2 × 1) [95]. The results obtained indicate that steps affect strongly the chemical, electronic and vibrational properties of these systems.…”

Section: Non-metal Surfacesmentioning

confidence: 95%

Bridging the structure gap: Chemistry of nanostructured surfaces at well-defined defects

Vattuone

Savio

Rocca

2008

Surface Science Reports

121

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Atomic geometry of steps on metal-oxide single crystals

Cited by 23 publications

References 15 publications

Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO₂(111) with Changing Annealing Condition

Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO₂(111) with Changing Annealing Condition

Iron oxide surfaces

Bridging the structure gap: Chemistry of nanostructured surfaces at well-defined defects

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Atomic geometry of steps on metal-oxide single crystals

Cited by 23 publications

References 15 publications

Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO2(111) with Changing Annealing Condition

Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO2(111) with Changing Annealing Condition

Iron oxide surfaces

Bridging the structure gap: Chemistry of nanostructured surfaces at well-defined defects

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Product

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Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO₂(111) with Changing Annealing Condition

Scanning Tunneling Microscope Study of Surface Morphology Variation of CeO₂(111) with Changing Annealing Condition