Ellipsometry-LEED study of oxygen adsorption and the carbon monoxide- oxygen interaction on Ag(110)

Albers, H.; Wal, W.J.J. van der; Gijzeman, O.L.J.; Bootsma, G.A.

doi:10.1016/0039-6028(78)90155-3

Cited by 83 publications

(19 citation statements)

References 13 publications

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“…These results strongly suggest that 6A is proportional to the oxygen coverage. It should be pointed out that similar relationships were obtained for oxygen on Ag(ll0) [25] and Cu( 110) [26] at room temperature. In this range for Cu( 111) the change in the other ellipsometric parameter 6 $ = l/3 6A.…”

Section: Determination Of Oxygen Coveragesupporting

confidence: 68%

A study of the kinetics of the interactions of O2 and N2O with a Cu(111) surface and of the reaction of CO with adsorbed oxygen using aes, LEED and ellipsometry

Habraken¹,

Kieffer²,

Bootsma³

1979

Surface Science

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219

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The ~teractions of 02 and N20 in the low pressure range with a Cu(ll1) surface and of CO with adsorbed oxygen have been studied with ellipsometry, Auger electron spectroscopy and LEED. The adsorption of 02 was investigated in the 10-6-104Torr range and at crystal temperatures ranging from 23 to 4OO'C. 02 chemisorbs dissociatively with an initial reaction probability of about 10m3 and an apparent activation energy of 2-4 kcal/mol, which depends on the substrate temperature, up to a saturation coverage of 0.45. The probability of decomposition of N20 is 10ms at 300°C, and the activation energy is 10.4 kcal/mol For 250 < T< 4OO'C. The oxygen coverage saturates at B = 0.45 as well. For both oxidation reactions the kinetics can be described with a precursor state model. With LEED no superstructures were observed. The probability of the reaction of CO with adsorbed oxygen is 4 X lo-' at 250°C and is initially independent of the oxygen coverage. The reaction is assumed to proceed via a Langmuir-Hinshelwood mechanism. The activation energy for the reaction COad + oad -+ CO* is 18-20 kcal/mol.

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Section: Determination Of Oxygen Coveragesupporting

confidence: 68%

A study of the kinetics of the interactions of O2 and N2O with a Cu(111) surface and of the reaction of CO with adsorbed oxygen using aes, LEED and ellipsometry

Habraken¹,

Kieffer²,

Bootsma³

1979

Surface Science

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219

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“…where 8' = 20; kl and k2 are the different rate constants for reaction with "row" oxygen atoms and with "lone" oxygen atoms respectively [17,4]. For fitting to the curves of fig.…”

Section: Discussionmentioning

confidence: 99%

The adsorption and incorporation of oxygen on Cu(110) and its reaction with carbon monoxide

et al. 1979

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The initial interaction of oxygen with a Cu(ll0) surface occurs in two stages, character&d by (2 X 1) and ~$6 X 2) overlayer structures and then a third stage where the cf6 X 2) structure remains but further oxygen uptake is registered only with e~psometry. The fust stage is nonactivated and is accornp~~~ by a work function increase of 370-420 meV, depending on sample temperature. The subsequent appearance of the extra features associated with the c(6 X 2) structure in the second stage is accompanied by a decrease in work function of -100 meV and is characterised by an apparent activation energy of -18 M mol-r . The adsorbed oxygen can be removed at all coverages by gas-phase CO. The reaction appears to foHOw Langmuir-Hiishelwood kinetics with an apparent activation energy of -25 M mol-' . fntroductionThe interaction of oxygen with the (110) surface of copper results in the initial formation of a (2 X 1) surface structure which is assumed to correspond to 0.5 monolayers [l--4]. Further oxygen exposure produces a ~(6 X 2) structure f5]. The first stage of the interaction is known to be accompanied by an increase in work function. Thus Ertl and Kiippers [6] have reported an increase of 0.2 eV after an exposure of 6 L and Delchar f7] a m~~urn increase of 0.67 eV after 2 X 10" L at room temperature. Delchar established that a change of 0.40 eV had already been reached after about 100 L. On the (100) surface a similar reaction sequence has been observed. The formation of the initial (u/z X 42) R45" structure is accompanied by an increase in the work function as might be expected, but the formation of the subsequent (d2 X 242) R4.5" structure by a decrease [8,9]. This has been 285

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“…(7) of ref. [ 181). The factor (NS -Nr)/IV, has been included to take account of the L-H mechanism and it denotes the probability that a site in a neighbouring [OOl] row is empty and available for CO molecules.…”

Section: The Oxidation Of Co By Preadsorbed Oxygenmentioning

confidence: 99%

The kinetics of the interactions of O2 and N20 with a Cu(110) surface and of the reaction of CO with adsorbed oxygen studied by means of ellipsometry, AES and LEED

1979

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Ellipsometry, LEED and Auger electron spectroscopy have been used to study the interactions of Oa and NzO with a clean annealed Cu(ll0) surface and the reaction of CO with adsorbed oxygen in the monolayer range. Gas pressures were in the range 1O-8-1O-4 Torr and crystal temperatures varied between 23-4OO'C. The changes in the ellipsometric angles A and $I per oxygen atom upon adsorption and removal of oxygen depend on the coverage 0, the temperature and on the azimuth of the plane of incidence of the light beam. The kinetics of the chemisorption of oxygen is independent of the crystal temperature, initial sticking probabiiity ~0.2. The LEED data and the adsorption kinetics indicate an attractive interaction in the adsorbed layer in the [OOl] direction. The initial decomposition probabi~~y of NaO at room temperature is 0.15 and decreases with increasing temperature; the maximum coverage is 0.5 monolayer. The LEED patterns observed were the same as those with 0s. The reaction probability of CO with adsorbed oxygen increases with decreasing oxygen coverage (order of mag nitude -1O-5, apparent activation energy -6 kcaI/mol). This increase has been attributed to the operation of the Langmuir-Hinshelwood mechanism.

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Ellipsometry-LEED study of oxygen adsorption and the carbon monoxide- oxygen interaction on Ag(110)

Cited by 83 publications

References 13 publications

A study of the kinetics of the interactions of O2 and N2O with a Cu(111) surface and of the reaction of CO with adsorbed oxygen using aes, LEED and ellipsometry

A study of the kinetics of the interactions of O2 and N2O with a Cu(111) surface and of the reaction of CO with adsorbed oxygen using aes, LEED and ellipsometry

The adsorption and incorporation of oxygen on Cu(110) and its reaction with carbon monoxide

The kinetics of the interactions of O2 and N20 with a Cu(110) surface and of the reaction of CO with adsorbed oxygen studied by means of ellipsometry, AES and LEED

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