Tuning the Growth Orientation of Epitaxial Films by Interface Chemistry

Gubo, Matthias; Ebensperger, Christina; Meyer, Wolfgang; Hammer, Lutz; Heinz, K.; Mittendorfer, Florian; Redinger, Josef

doi:10.1103/physrevlett.108.066101

Cited by 28 publications

(35 citation statements)

References 32 publications

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“…We take advantage of the fact that a variety of well-ordered Co 3 O 4 and CoO films can be grown on Ir(100). [34][35][36][37][38] In a unique fashion these films allow to vary the stoichiometry, the surface orientation, the film thickness, and the defect density. Over the last years many of these structures have been characterized in great detail using low energy electron diffraction (LEED) I-V analysis and scanning tunneling microscopy (STM).…”

Section: Page 2 Of 32 Acs Paragon Plus Environmentmentioning

confidence: 99%

Adsorption and Activation of CO on Co₃O₄(111) Thin Films

et al. 2015

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To explore the catalytic properties of cobalt oxide at the atomic level, we have studied the interaction of CO and O 2 with well-ordered Co 3 O 4 (111) thin films using scanning tunneling microscopy (STM), high-resolution X-ray photoelectron spectroscopy (HR-XPS), infrared reflection absorption spectroscopy (IRAS), and temperature-programmed desorption spectroscopy (TPD) under ultrahigh vacuum (UHV) conditions. At low coverage and temperature CO binds to surface Co 2+ ions on the (111) facets. At larger exposure a compressed phase is formed in which additional CO is located at sites in between the Co 2+ ions. In addition a bridging carbonate species forms which is associated with defects such as step edges of Co 3 O 4 (111) terraces or the side facets of the (111) oriented grains. Preadsorbed oxygen neither affects CO adsorption at low coverage nor the formation of the surface carbonate but it blocks formation of the high coverage CO phase. Desorption of the molecularly bound CO occurs up to 180 K, whereas the surface carbonate decomposes in a broad temperature range up to 400 K under the release of CO and, to a lesser extent, of CO 2 .Upon strong loss of crystalline oxygen the Co 3 O 4 grains eventually switch to the CoO rocksalt structure.

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Section: Page 2 Of 32 Acs Paragon Plus Environmentmentioning

confidence: 99%

Adsorption and Activation of CO on Co₃O₄(111) Thin Films

et al. 2015

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“…33,34 Here, various other factors were considered, in particular the presence of oxygen vacancies and surface Co 2+ ions. [38][39][40][41][42][43][44][45][46][47][48] In a unique fashion, these films allow varying the stoichiometry, the surface orientation, the film thickness, and the defect density. 29 The present work aims at the development of new cobaltoxide-based model systems which allow us to study their surface chemistry under well-controlled ultrahigh vacuum (UHV) conditions.…”

Section: Introductionmentioning

confidence: 99%

Thermal evolution of cobalt deposits on Co₃O₄(111): atomically dispersed cobalt, two-dimensional CoO islands, and metallic Co nanoparticles

Mehl

Ferstl

Schuler

et al. 2015

Phys. Chem. Chem. Phys.

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Cobalt oxide nanomaterials show high activity in several catalytic reactions thereby offering the potential to replace noble metals in some applications. We have developed a well-defined model system for partially reduced cobalt oxide materials aiming at a molecular level understanding of cobalt-oxide-based catalysis. Starting from a well-ordered Co3O4(111) film on Ir(100), we modified the surface by deposition of metallic cobalt. Growth, structure, and adsorption properties of the cobalt-modified surface were investigated by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and infrared reflection absorption spectroscopy (IRAS) using CO as a probe molecule. The deposition of a submonolayer of cobalt at 300 K leads to the formation of atomically dispersed cobalt ions distorting the surface layer of the Co3O4 film. Upon annealing to 500 K the Co ions are incorporated into the surface layer forming ordered two-dimensional CoO islands on the Co3O4 grains. At 700 K, Co ions diffuse from the CoO islands into the bulk and the ordered Co3O4(111) surface is restored. Deposition of larger amounts of Co at 300 K leads to formation of metallic Co aggregates on the dispersed cobalt phase. The metallic particles sinter at 500 K and diffuse into the bulk at 700 K. Depending on the degree of bulk reduction, extended Co3O4 grains switch to the CoO(111) structure. All above structures show characteristic CO adsorption behavior and can therefore be identified by IR spectroscopy of adsorbed CO.

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“…11 The interest in one-layer-thick oxides is manifold, in particular (i) two-dimensional oxides can be seen as model systems for the oxide/metal interface, allowing investigation by means of high-resolution scanning probe techniques; (ii) the vertical confinement and the elastic and electronic coupling with the metallic substrate allows stabilizing stoichiometries and atomic structures that can differ with respect to the corresponding bulk terminations, with important implications in chemical reactivity, 12,13 adsorption properties, 14 and magnetic ordering 15 of the resulting structures; and (iii) the wetting layer can represent the precursor phase for the growth of thicker films. 16,17 Single layers of transition metal oxides have been stabilized on noble and quasinoble metals such as, for instance, Pd, 18,19 Ag, 20,21 Pt, 22,23 Au, 24 and Ir. 25 In these cases, growth techniques such as reactive deposition (i.e., metal deposition in oxygen atmosphere) and/or postoxidation are typically applied, leading to ordered phases and well-defined oxidemetal interfaces.…”

Section: Introductionmentioning

confidence: 99%

Self-organized chromium oxide monolayers on Fe(001)

et al. 2013

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The oxygen-saturated Fe(001)-p(1 × 1)O surface has been used as a template to stabilize two-dimensional Cr oxides on Fe(001). Cr deposition at 400 • C leads to two different well-ordered phases, depending on the amount of Cr deposited. In the submonolayer regime a novel c(4 × 2) overlayer self-assembles on the Fe(001)-p(1 × 1)O surface, saturating for a coverage of about 0.75 monolayers. This phase becomes unstable for higher coverages, when a ( √ 5 × √ 5)R27 • superstructure emerges. The structural and electronic details of the two one-layer-thick oxides are studied by combining high-resolution scanning tunneling microscopy, low-energy electron diffraction, Auger electron spectroscopy, and density functional theory.

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Tuning the Growth Orientation of Epitaxial Films by Interface Chemistry

Cited by 28 publications

References 32 publications

Adsorption and Activation of CO on Co₃O₄(111) Thin Films

Adsorption and Activation of CO on Co₃O₄(111) Thin Films

Thermal evolution of cobalt deposits on Co₃O₄(111): atomically dispersed cobalt, two-dimensional CoO islands, and metallic Co nanoparticles

Self-organized chromium oxide monolayers on Fe(001)

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Tuning the Growth Orientation of Epitaxial Films by Interface Chemistry

Cited by 28 publications

References 32 publications

Adsorption and Activation of CO on Co3O4(111) Thin Films

Adsorption and Activation of CO on Co3O4(111) Thin Films

Thermal evolution of cobalt deposits on Co3O4(111): atomically dispersed cobalt, two-dimensional CoO islands, and metallic Co nanoparticles

Self-organized chromium oxide monolayers on Fe(001)

Contact Info

Product

Resources

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Adsorption and Activation of CO on Co₃O₄(111) Thin Films

Adsorption and Activation of CO on Co₃O₄(111) Thin Films

Thermal evolution of cobalt deposits on Co₃O₄(111): atomically dispersed cobalt, two-dimensional CoO islands, and metallic Co nanoparticles