Structure and growth of crystalline superlattices: From monolayer to superlattice

Bauer, E.; Merwe, Jan H. van der

doi:10.1103/physrevb.33.3657

Cited by 633 publications

(282 citation statements)

References 60 publications

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“…If heteroepitaxial growth takes place close to equilibrium conditions, the growth mode depends on the surface free energies of the substrate γ s and the film γ f as well as on the interfacial energy γ i,n [263]. The interfacial energy γ i,n depends on the specific chemical interaction between film and substrate atoms at the interface.…”

Section: Discussionmentioning

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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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: Discussionmentioning

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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“…[7] As a result, the deposition speed increased and island growth became dominant, leading to a porous structure of the film. [8][9][10] It could be shown that an elevated substrate temperature compensated this effect in part, but leading to a lower deposition speed. However, these films were characterized by high internal tension causing reduced substrate adhesion.…”

Section: Introductionmentioning

confidence: 99%

“…[6] It could be shown that this discharge mode in conjunction with a symmetric mixing of the vaporized precursor with the surrounding cylindrically rotating plasma at the outlet of the capillary leads to a significantly enhanced homogeneity of the profile and chemical composition of the deposited films as compared to a plasma jet with irregular discharge filaments. [6] SiO x films with exceptionally low carbon content and a high degree of cross-linkage could be deposited using OMCTS [octamethylcyclotetrasiloxane, Si 4 8 ]. An experimental study on the influence of the O 2 versus OMCTS concentration on the chemical composition of the films and their radial gradients over the static deposition profile is carried out by means of XPS and ATR-FTIR.…”

Section: Introductionmentioning

confidence: 99%

Chemical Composition of SiO_x Films Deposited by an Atmospheric Pressure Plasma Jet (APPJ)

Schäfer

Foest

Quade

et al. 2009

Plasma Processes & Polymers

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SiOx films are deposited with an APPJ (27 MHz) using Ar, O2 and OMCTS [Si4O4(CH3)8]. An experimental study on the influence of the O2 versus OMCTS concentration on the chemical composition of the films and their radial gradients over the static deposition profile is carried out by means of XPS and ATR‐FT‐IR. The films are characterized by dominating SiO IR absorption and the absence of CH2 and CH3 bands, indicating the inorganic SiOx character. From the absorbance differences of the three SiO IR bands present in the spectra, the existence of different structural phases is derived. Over the examined parameter field, three different structural phases are distinguished. Their occurrence can be seen as a marker for the film quality and allows formulating optimal deposition conditions for defined structures of organosilicon films.

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“…Recently, there has been much interest [1][2][3][4][5][6][7][8][9][10][11][12][13][14] in growth of epitaxial metal films and superlattices due to their unusual physical properties. The quality and structure of these systems is of paramount importance for applications.…”

Section: Introductionmentioning

confidence: 99%

Effects of anharmonic strain on the phase stability of epitaxial films and superlattices: Applications to noble metals

1998

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Epitaxial strain energies of epitaxial films and bulk superlattices are studied via first-principles total energy calculations using the local-density approximation. Anharmonic effects due to large lattice mismatch, beyond the reach of the harmonic elasticity theory, are found to be very important in Cu/Au (lattice mismatch 12%), Cu/Ag (12%) and Ni/Au (15%). We find that 001 is the elastically soft direction for biaxial expansion of Cu and Ni, but it is 201 for large biaxial compression of Cu, Ag, and Au. The stability of superlattices is discussed in terms of the coherency strain and interfacial energies. We find that in phase-separating systems such as Cu-Ag the superlattice formation energies decrease with superlattice period, and the interfacial energy is positive. Superlattices are formed easiest on (001) and hardest on (111) substrates. For ordering systems, such as Cu-Au and Ag-Au, the formation energy of superlattices increases with period, and interfacial energies are negative. These superlattices are formed easiest on (001) or (110) and hardest on (111) substrates. For NiAu we find a hybrid behavior: superlattices along 111 and 001 behave like in phase-separating systems, while for 110 they behave like in ordering systems. Finally, recent experimental results on epitaxial stabilization of disordered Ni-Au and Cu-Ag alloys, immiscible in the bulk form, are explained in terms of destabilization of the phase separated state due to lattice mismatch between the substrate and constituents.

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Structure and growth of crystalline superlattices: From monolayer to superlattice

Cited by 633 publications

References 60 publications

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

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

Chemical Composition of SiO_x Films Deposited by an Atmospheric Pressure Plasma Jet (APPJ)

Effects of anharmonic strain on the phase stability of epitaxial films and superlattices: Applications to noble metals

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Structure and growth of crystalline superlattices: From monolayer to superlattice

Cited by 633 publications

References 60 publications

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

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

Chemical Composition of SiOx Films Deposited by an Atmospheric Pressure Plasma Jet (APPJ)

Effects of anharmonic strain on the phase stability of epitaxial films and superlattices: Applications to noble metals

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Chemical Composition of SiO_x Films Deposited by an Atmospheric Pressure Plasma Jet (APPJ)