Biphase Ordering of Iron Oxide Surfaces

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

doi:10.1103/physrevlett.75.1961

Cited by 126 publications

(166 citation statements)

References 11 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: 58%

“…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%

“…Other orientations have to be prepared by the usual procedure of cutting, polishing, sputtering and annealing in vacuum or in O 2 atmosphere. Many metal-oxide surfaces have been prepared in this way as reviewed in [4][5][6], also among these are several surface planes of Fe 3 O 4 and α-Fe 2 O 3 single-crystals [135][136][137][138][139][140][141]. However, single-crystal samples may cause several experimental problems.…”

Section: Preparation Of Ordered Metal-oxide Surfacesmentioning

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: 58%

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

confidence: 99%

Section: Preparation Of Ordered Metal-oxide Surfacesmentioning

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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“…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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“…2c) as well as regions where no such domains have formed. In analogy to the ´biphase ordering´ [22,23] Upon further oxidation for 20 min, the satellite LEED pattern of the FeO(111) film vanishes and the normal Fe 3 O 4 (111) pattern with the unexpanded lattice constant of ~6 Å [20] appears (fig. 3a).…”

mentioning

confidence: 99%

Self-assembled periodicFe3O4nanostructures in ultrathin FeO(111) films on Ru(0001)

Ketteler

Ranke

2002

Phys. Rev. B

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(9)Low energy electron diffraction and scanning tunneling microscopy studies of FeO(111 ) films on Ru(0001) show formation of coincidence structures with a Moiré pattern up to a thickness of four monolayers. In the four monolayer thick film, strained conducting Fe3O4(111) nano-domains nucleate in the insulating FeO(111) matrix and form an ordered inverse biphase superstructure. Further oxidation causes these domains to grow and to coalesce into a closed Fe3O4(111) film.

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Biphase Ordering of Iron Oxide Surfaces

Cited by 126 publications

References 11 publications

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

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

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

Self-assembled periodicFe3O4nanostructures in ultrathin FeO(111) films on Ru(0001)

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