Scanning tunnelling microscopy studies of α-Fe2O3(0001)

Condon, N.G.; Leibsle, F.M.; Lennie, Alistair R.; Murray, P. W.; Parker, Timothy M.; Vaughan, David J.; Thornton, G.

doi:10.1016/s0039-6028(97)00744-9

Cited by 77 publications

(77 citation statements)

References 22 publications

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“…A biphase structure, interpreted as coexisting islands of α-Fe 2 O 3 (0001) and FeO(111) phases, was observed. These phases existed in domains forming a superstructure with a periodicity of about 40 Å [138,288]. The same superstructure is obtained on the epitaxial film shown in Fig.…”

Section: Discussionsupporting

confidence: 74%

“…Pure FeO(111) surfaces could be prepared by continued cycles of sputtering and annealing at 1000 K. On an α-Fe 2 O 3 (0001) single-crystal, prepared in a similar way, islands forming a superstructure with a periodicity of about 40 Å was formed. This biphase structure was interpreted as coexisting islands of α-Fe 2 O 3 (0001) and FeO(111) phases with the latter being formed on top of the underlying α-Fe 2 O 3 (0001) substrate, because of the reducing preparation conditions applied [138,288]. The longe-range superstructure was explained by the lattice mismatch between the two types of O sublattices involved.…”

Section: (I) Biphase Structures Formed Below T=1000 Kmentioning

confidence: 99%

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Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Weiß

Ranke

2002

Progress in Surface Science

579

610

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Metal-oxide based catalysts are used for many important synthesis reactions in the chemical industry. A better understanding of the catalyst operation can be achieved by studying elemantary reaction steps on well-defined model catalyst systems. For the dehydrogenation of ethylbenzene to styrene in the presence of steam both unpromoted and potassium promoted iron-oxide catalysts are active. Here we review the work done over unpromoted single-crystalline FeO(111), Fe 3 O 4 (111) and α-Fe 2 O 3 (0001) films grown epitaxially on Pt(111) substrates. Their geometric and electronic surface structures were characterized by STM, LEED, electron microscopy and electron spectroscopic techniques. In an integrative approach, the interaction of water, ethylbenzene and styrene with these films was investigated mainly by thermal desorption and photoelectron emission spectroscopy. The adsorptiondesorption energetics and kinetics depend on the oxide surface terminations and are correlated to the electronic structures and acid-base properties of the corresponding oxide phases, which reveal insight into the nature of the active sites and into the catalytic function of semiconducting oxides in general. Catalytic studies, using a batch reactor arrangement at high gas pressures and post reaction surface analysis, showed that only α-Fe 2 O 3 (0001) containing surface defects is catalytically active, whereas Fe 3 O 4 (111) is always inactive. This can be related to the elementary adsorption and desorption properties observed in ultrahigh vacuum, which indicates that the surface chemical properties of the iron-oxide films do not change significantly across the "pressure-gap". A model is proposed according to which the active site involves a regular acidic surface sites and a defect site next to it. The results on metal-oxide surface chemistry also have implications for other fields, such as environmental science, biophysics and chemical sensors.-2 -"2kyEi9FYSQjBVrZxIPQ.FHIAC_WRa02_review.doc", Datum: 19.02.03

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Section: Discussionsupporting

confidence: 74%

Section: (I) Biphase Structures Formed Below T=1000 Kmentioning

confidence: 99%

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Weiß

Ranke

2002

Progress in Surface Science

579

610

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“…It has been found that the surface structure obtained in the present study is different from those of the bulk metallic iron 2,3) and other iron oxides such as Fe 3 O 4 4-8) and Fe 2 O 3 , [9][10][11] which have been investigated on the various crystallographic orientations. Therefore, the composition of observed surface remains Fe 1Ϫx O, and is not changed to Fe or other iron oxides by annealing.…”

Section: Discussioncontrasting

confidence: 54%

Nonstoichiometric Wüstite (001) Surface Exposing Defect Clusters

et al. 2011

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The (001) surface of nonstoichiometric wüstite (Fe 0.94 O) grown by the floating zone technique was investigated using STM, LEED and AES. Two distinctive structures, i.e., the dents arrangement and the FeO(001)-c(4ϫ2) reconstructed structure coexist on the terrace after annealing at 1 073 K in the ultrahigh vacuum (UHV) system. On the other hand, the only dents exist after annealing at 1 273 K. The dent is the Fe vacancy pair in the rocksalt-type FeO(001)-(1ϫ1) matrix, which is the exposed PЈ phase of the defect cluster due to nonstoichiometry.

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“…Earlier investigations of the (0001) surface of both bulk α-Fe 2 O 3 and epitaxial thin films, using qualitative low energy electron diffraction (LEED) [140][141][142][143][144] and scanning tunneling microscope (STM) [145][146][147][148][149][150], have shown significant variations in the nature of the surface ordering depending on the method of surface preparation. Detailed structural characterization of the {0001} surface under ultrahigh vacuum and clean conditions revealed that both Fe-and O-terminations coexist under different conditions of temperature and oxygen partial pressure [149][150][151][152].…”

Section: The Structure Of α-Fe 2 O 3 Surfacesmentioning

confidence: 99%

A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3) Surfaces

2014

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Abstract:The reactivity of mineral surfaces in the fundamental processes of adsorption, dissolution or growth, and electron transfer is directly tied to their atomic structure. However, unraveling the relationship between the atomic surface structure and other physical and chemical properties of complex metal oxides is challenging due to the mixed ionic and covalent bonding that can occur in these minerals. Nonetheless, with the rapid increase in computer processing speed and memory, computer simulations using different theoretical techniques can now probe the nature of matter at both the atomic and sub-atomic levels and are rapidly becoming an effective and quantitatively accurate method for successfully predicting structures, properties and processes occurring at mineral surfaces. In this study, we have used Density Functional Theory calculations to study the adsorption of benzene on hematite (α-Fe 2 O 3 ) surfaces. The strong electron correlation effects of the Fe 3d-electrons in α-Fe 2 O 3 were described by a Hubbard-type on-site Coulomb repulsion (the DFT+U approach), which was found to provide an accurate description of the electronic and magnetic properties of hematite. For the adsorption of benzene on the hematite surfaces, we show that the adsorption geometries parallel to the surface are energetically more stable than the vertical ones. The benzene molecule interacts with the hematite surfaces through π-bonding in the parallel adsorption geometries and through weak hydrogen bonds in the vertical geometries. Van der Waals interactions are found to play a significant role in stabilizing the absorbed benzene molecule. Analyses of the electronic structures reveal that upon benzene adsorption, the conduction band edge of the surface atoms is shifted towards the valence bands, thereby considerably reducing the band gap and the magnetic moments of the surface Fe atoms. OPEN ACCESSMinerals 2014, 4 90

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Scanning tunnelling microscopy studies of α-Fe2O3(0001)

Cited by 77 publications

References 22 publications

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Nonstoichiometric Wüstite (001) Surface Exposing Defect Clusters

A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3) Surfaces

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