Electron-stimulated desorption of atomic oxygen from polycrystalline Ag

Outlaw, R. A.; Hoflund, Gar B.; Corallo, Gregory R.

doi:10.1016/0169-4332(87)90125-5

Cited by 58 publications

(5 citation statements)

References 23 publications

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“…6. This is in agreement with other neutral ESD measurements on O/W͑110͒, 4,6 O/W͑poly͒, 4 CO/W͑110͒, 6 and O/Ag͑poly͒, 39 where no isotope effect was found.…”

Section: The Neutral Co Yield: Summary Of Resultssupporting

confidence: 93%

Isotope effect in electron stimulated desorption: The role of internal degrees of freedom in CO desorption from Pt(111)

Szabó¹,

Yates²

1995

The Journal of Chemical Physics

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Width of particle beams desorbed in electron stimulated desorption: O+ and metastable CO from CO/Pt(111) J. Chem. Phys. 98, 689 (1993); 10.1063/1.464614Rotational dynamics and electronic energy partitioning in the electronstimulated desorption of NO from Pt (111) Electron stimulated desorption ͑ESD͒ of CO ϩ , O ϩ , metastable neutral CO*, and ground state neutral CO from the CO/Pt͑111͒ was studied, using isotopic substitution of CO. Four isotopic versions of CO were compared in their desorption behavior. Contrary to the prediction of theoretical models that suggest a decrease of the ESD yield with increasing mass of a given desorption product, the CO ϩ and CO* ESD yields were found to be larger from the ͑heavier͒ 12 C 18 O than from the ͑lighter͒ 13 C 16 O adsorbate. The O ϩ ESD yields followed the expected trend Y ͑ 16 O ϩ ͒ϾY ͑ 18 O ϩ ͒. No isotope effect was observed for ground state neutral CO desorption. Qualitative arguments explaining the anomalous isotope effect, and emphasizing the importance of internal dynamics, in particular, the rotation of diatomic desorption products in the ESD process, are presented. Here it is shown that the velocity of departure of the carbon end of the rotating CO molecule may control neutralization or quenching effects for CO ϩ or CO* produced by electron stimulated desorption. Thus, neutralization or quenching of the excited CO species occurs via carbon-centered orbitals of the departing species.

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“…6. This is in agreement with other neutral ESD measurements on O/W͑110͒, 4,6 O/W͑poly͒, 4 CO/W͑110͒, 6 and O/Ag͑poly͒, 39 where no isotope effect was found.…”

Section: The Neutral Co Yield: Summary Of Resultssupporting

confidence: 93%

Isotope effect in electron stimulated desorption: The role of internal degrees of freedom in CO desorption from Pt(111)

Szabó¹,

Yates²

1995

The Journal of Chemical Physics

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“…Since neutral ESD species are difficult to detect, very few ESD studies of neutral species have appeared in the literature. The neutral atom flux has been detected by using a quadrupole mass spectrometer , in the appearance potential (AP) mode to allow the atoms to be distinguished from residual gases and background gas products formed by collisions of the neutrals with the walls of the UHV system. In this experiment the ion acceleration potential was set at 0.0 V. Calibration studies have demonstrated that the ions entering the quadrupole section must have a minimum kinetic energy of 2.0 eV to reach the detector so the ESD neutrals detected have a minimum energy of 2.0 eV.…”

Section: Methodsmentioning

confidence: 99%

Erosion Study of Poly(ethylene tetrafluoroethylene) (Tefzel) by Hyperthermal Atomic Oxygen

Everett

Hoflund

2004

Macromolecules

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In this study the erosion of poly(ethylene tetrafluoroethylene) (ETFE) (Tefzel) by hyperthermal atomic oxygen (AO) has been examined using X-ray photoelectron spectroscopy (XPS). Initially, the Tefzel film had F/C and O/C atom ratios of 0.74 and 0.04, which decrease to 0.17 and 0.01, respectively, after a 2 h exposure to a flux of 2 × 1015 atoms/(cm2 s) AO with an average kinetic energy of 5 eV. The F/C atom ratio is further reduced to 0.02 with longer AO exposures, essentially producing a graphitic or amorphous carbon-like layer with a carbon content greater than 90 at. %. Longer AO exposures do not alter the composition of this layer significantly. Exposure of the AO-damaged surface to O2 or air nearly doubles the oxygen content in the near-surface region. This is due to dissociative oxygen adsorption at reactive sites formed at the polymer surface during AO exposure. Further exposure to AO removes this chemisorbed oxygen. C−H bonds are important sites for attack during erosion by hyperthermal AO.

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“…Since neutral ESD species are difficult to detect, very few ESD studies of neutral species have appeared in the literature. The neutral-atom flux has been detected using a quadrupole mass spectrometer , in the appearance potential (AP) mode to allow the atoms to be distinguished from residual gases and background gas products formed by collisions of the neutrals with the walls of the UHV system. In this experiment, the ion acceleration potential was set at 0.0 V. Calibration studies have demonstrated that the ions entering the quadrupole section must have a minimum kinetic energy of 2.0 eV to reach the detector, so the ESD neutrals detected have a minimum energy of 2.0 eV.…”

Section: Methodsmentioning

confidence: 99%

Chemical Alteration of Poly(tetrafluoroethylene) (TFE) Teflon Induced by Exposure to Hyperthermal Atomic Oxygen

and

Everett

2004

J. Phys. Chem. B

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In this study, the erosion of poly(tetrafluoroethylene) TFE Teflon by hyperthermal atomic oxygen (AO) has been examined using X-ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 1.66 decreases to 1.15 after a 2 h exposure to a flux of 2 × 1015 atoms/cm2 s AO with an average kinetic energy ∼5 eV. The F/C atom ratio is further reduced to a value of 0.90 after a 25 h exposure. The high-resolution XPS C 1s data indicate that new chemical states of carbon form as the F is removed, and that the relative amounts of these states depend on the F content of the near-surface region. The states are most likely due to C bonded only to one F atom and C bonded only to other C atoms. Exposures of the AO-damaged surface to research-grade O2 results in chemisorption of a very small amount of O (∼0.8 at. %); this indicates that large quantities of reactive sites are not formed during the chemical erosion by AO. Further exposure to AO removes this chemisorbed oxygen. After exposing the AO-exposed surface to air for 90 min, O2 is chemisorbed and the F/C atom ratio is reduced to 0.68. Another 46 h of AO exposure results in removal of this O and a further decrease in the F/C atom ratio to 0.58.

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Electron-stimulated desorption of atomic oxygen from polycrystalline Ag

Cited by 58 publications

References 23 publications

Isotope effect in electron stimulated desorption: The role of internal degrees of freedom in CO desorption from Pt(111)

Isotope effect in electron stimulated desorption: The role of internal degrees of freedom in CO desorption from Pt(111)

Erosion Study of Poly(ethylene tetrafluoroethylene) (Tefzel) by Hyperthermal Atomic Oxygen

Chemical Alteration of Poly(tetrafluoroethylene) (TFE) Teflon Induced by Exposure to Hyperthermal Atomic Oxygen

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