| Autor: |
C. Schwennicke, H. Pfnür, E. Schmidtke |
| Rok vydání: |
1994 |
| Předmět: |
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| Zdroj: |
Surface Science. 312:301-309 |
| ISSN: |
0039-6028 |
| DOI: |
10.1016/0039-6028(94)90723-4 |
| Popis: |
The adsorption geometry and the adsorbate induced relaxations of p (2 × 2 ) ordered oxygen on Ni (111) have been reinvestigated by a dynamical LEED analysis in the energy range between 30 and 387 eV. 14 non-equivalent beams have been recorded with a total energy range of 2830 eV. Vertical distances, buckling and lateral shifts including rotations have been tested for the adsorbate and the first 2 substrate layers. Top and the three-fold coordinated hcp and fcc sites were tested as adsorption sites. While the top site can be excluded already by tests on the non-buckled surface the discrimination between hcp and the strongly favoured fcc sites is only possible if buckling is included in the model calculations. Optimal agreement between calculated and experimental curves (Rp = 0.226) was obtained for a Ni-O nearest neighbour distance of 1.83 A. Significant buckling up to 0.09 A was found in the first 2 substrate layers, but the average Ni-Ni layer distance is only slightly (0.02 A) expanded between the first and second substrate layer, and corresponds to the bulk value (2.03 A) for the other layers. Adsorbate induced lateral shifts (0.02 ± 0.04 A) for nearest neighbours of O) turned out to be at the limit of detectability already in the first substrate layer. No indication could be found for adsorbate induced rotational shifts in the topmost substrate layers. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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