The effect of sputter temperature on vacancy island behavior on Ni(111) measured by photoemission of adsorbed xenon

Malafsky, Geoffrey P.

doi:10.1016/0039-6028(94)91174-6

Cited by 4 publications

(4 citation statements)

References 22 publications

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“…We suspect, however, that this value is at best an upper limit, since a background pressure of 3 × 10 -5 Torr may not lead to a saturation coverage of Xe. It is difficult to convert the area ratios into relative site concentrations, since prior research has shown that there need not be a 1:1 correspondence between Xe adsorption and site concentration. , Every defect or sulfur-deficient site, for example, may bind more Xe than does the site responsible for the −670 eV Xe feature. On the basis of the relative areas of the Xe 3d 5/2 features, however, we infer that this latter site is more abundant than the defect site.…”

Section: Discussionmentioning

confidence: 99%

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H₂O on FeS₂(100)

1998

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The reaction of H2O with the (100) crystallographic plane of pyrite, FeS2, has been investigated in the vacuum environment with photoemission of adsorbed xenon (PAX), temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). TPD data indicate that H2O desorbs from FeS2(100) in a broad range of temperatures (150−300 K). XPS data suggests that the vast majority of H2O that initially adsorbs on pyrite at 79 K desorbs from pyrite during thermal annealing to 300 K. PAX, a technique that is sensitive to the short range order of a surface, has been used to elucidate the types of sites that are available on FeS2(100) for the binding of adsorbate. Within the resolution of our PAX data, the surface of FeS2(100) consists of at least two types of sites. It is proposed that these two types of sites are associated with the stoichiometric surface and defect (i.e., sulfur-deficient or anion vacancy) sites. PAX further suggests that at low adsorbate coverage, H2O predominately resides on defect sites. As the coverage of H2O is increased, defect sites become saturated and additional adsorption occurs on the less reactive stoichiometric surface.

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Section: Discussionmentioning

confidence: 99%

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H₂O on FeS₂(100)

1998

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“…1). This is only an estimate, because saturation may not of been achieved under our experi-mental conditions, and the amount of Xe that adsorbs on a given defect site need not be equal to the amount of Xe that adsorbs on a stoichiometric surface site (Malafsky 1994).…”

Section: Thermal Chemistry Of H 2 O On Fes 2 (100)mentioning

confidence: 95%

“…8). As stated above, prior research also has shown the difficulties in obtaining site concentrations through the use of PAX (Malafsky 1994).…”

Section: Thermal Chemistry Of H 2 S On Fes 2 (100)mentioning

confidence: 99%

Thermal chemistry of H₂S and H₂O on the (100) plane of pyrite; unique reactivity of defect sites

Guevremont

Strongin

Schoonen

1998

American Mineralogist

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The interaction of a natural face of FeS 2 (100), cleaned in ultra-high vacuum (UHV), with H 2 O and H 2 S has been investigated with X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and the photoemission of adsorbed xenon (PAX). PAX is sensitive to the short-range order of the surface and allows the effects of defects on the surface reactivity of FeS 2 (100) to be studied. PAX results suggest that both H 2 S and H 2 O bind most strongly to defect sites that we propose are, at least in part, sulfur anion vacancy sites. Whereas the majority of H 2 O adsorbate desorbs from these sites in the temperature interval of 200-300 K, H 2 S dissociates upon heating to 500 K into adsorbed surface hydrogen, S, and SH. This dissociation occurs on defect sites that then release part of the dissociation fragment, which is thought to be surface hydrogen, onto other regions of the pyrite surface that are proposed to be stoichiometric FeS 2. Heating to 600 K causes further reaction of S containing dissociation fragments with sulfur-deficient sites to form new surface sites that resemble FeS 2. The results also suggest that surface hydrogen dissolves into the pyrite bulk upon heating to 600 K.

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“…Monolayer vacancy islands have been generated on a variety of transition metal surfaces. ,− The appropriate temperatures for preparing different sizes of vacancy islands will scale with the substrate melting temperature since the preparation process involves a tradeoff between the efficiency of atom removal by sputtering and the rate of substrate atom diffusion on the surface. As described in detail by Michely et al, the 3-fold symmetrical shape of the vacancy islands (e.g., Figure ) is the result of 3-fold symmetry of the Pt(111) substrate.…”

Section: Resultsmentioning

confidence: 99%

Controlled Size, Nanometer-Scale, Reaction Vessels in Two Dimensions

2000

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Islands of monolayer vacancies can be generated on transition metal surfaces by ion bombardment of samples held at elevated temperature. Our experiments show that the average size of the monolayer vacancy islands can be varied in a controlled manner from 3 to 30 nm by adjusting the sample temperature. We also demonstrate that monolayer vacancy islands can be used as two-dimensional nanometer-scale catalytic “reaction vessels.” The reactants are confined to the reaction vessels by energetic barriers to adsorbate diffusion across the atomic steps that form the walls of the vessels. Reaction vessels with diameters of ∼3 nm can accommodate only a small number of reactant molecules (e.g., a maximum of 28 ethylene molecules can be adsorbed in an area with a diameter of 3.3 nm on a Pt(111) surface). Reactions whose products or rates depend on the number of reactant molecules that are available can be controlled using these reaction vessels. This is demonstrated for the particular example of carbon particles that are formed from the dehydrogenation of mono-olefins on Pt.

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The effect of sputter temperature on vacancy island behavior on Ni(111) measured by photoemission of adsorbed xenon

Cited by 4 publications

References 22 publications

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H₂O on FeS₂(100)

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H₂O on FeS₂(100)

Thermal chemistry of H₂S and H₂O on the (100) plane of pyrite; unique reactivity of defect sites

Controlled Size, Nanometer-Scale, Reaction Vessels in Two Dimensions

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The effect of sputter temperature on vacancy island behavior on Ni(111) measured by photoemission of adsorbed xenon

Cited by 4 publications

References 22 publications

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H2O on FeS2(100)

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H2O on FeS2(100)

Thermal chemistry of H2S and H2O on the (100) plane of pyrite; unique reactivity of defect sites

Controlled Size, Nanometer-Scale, Reaction Vessels in Two Dimensions

Contact Info

Product

Resources

About

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H₂O on FeS₂(100)

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H₂O on FeS₂(100)

Thermal chemistry of H₂S and H₂O on the (100) plane of pyrite; unique reactivity of defect sites