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The adsorption geometry of sulphur on Ir{1 0 0}: A quantitative LEED study
Ist Teil von
Surface science, 2006-02, Vol.600 (4), p.880-889
Ort / Verlag
Lausanne: Elsevier B.V
Erscheinungsjahr
2006
Link zum Volltext
Quelle
Elsevier ScienceDirect Journals Complete
Beschreibungen/Notizen
A quantitative low energy electron diffraction (LEED) analysis has been performed for the p(2
×
2)-S and c(2
×
2)-S surface structures formed by exposing the (1
×
1) phase of Ir{1
0
0} to H
2S at 750
K. S is found to adsorb on the fourfold hollow sites in both structures leading to Pendry
R-factor values of 0.17 for the p(2
×
2)-S and 0.16 for the c(2
×
2)-S structures. The distances between S and the nearest and next-nearest Ir atoms were found to be similar in both structures: 2.36
±
0.01
Å and 3.33
±
0.01
Å, respectively. The buckling in the second substrate layer is consistent with other structural studies for S adsorption on fcc{1
0
0} transition metal surfaces: 0.09
Å for p(2
×
2)-S and 0.02
Å for c(2
×
2)-S structures. The (1
×
5) reconstruction, which is the most stable phase for clean Ir{1
0
0}, is completely lifted and a c(2
×
2)-S overlayer is formed after exposure to H
2S at 300
K followed by annealing to 520
K. CO temperature-programmed desorption (TPD) experiments indicate that the major factor in the poisoning of Ir by S is site blocking.