Pt25Rh75(111), (110), and (100) studied by scanning tunnelling microscopy with chemical contrast
| Autor: | Michael Schmid, E.L.D. Hebenstreit, Peter Varga, W. Hebenstreit |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
Annealing (metallurgy)
Alloy chemistry.chemical_element Surfaces and Interfaces engineering.material Condensed Matter Physics Surfaces Coatings and Films Rhodium law.invention Crystallography chemistry law Microscopy Materials Chemistry engineering Scanning tunneling microscope Platinum Surface reconstruction Quantum tunnelling |
| Zdroj: | Surface Science. 441:441-453 |
| ISSN: | 0039-6028 |
| DOI: | 10.1016/s0039-6028(99)00880-8 |
| Popis: | Scanning tunnelling microscopy images with chemical contrast allowed the direct determination of the composition and short-range order behaviour of the clean Pt 25 Rh 75 (111), (110), and (100) alloy surfaces. All measurements were performed at room temperature and showed a strong platinum enrichment depending on the preparation temperature. In the top layers of both Pt 25 Rh 75 (111) and Pt 25 Rh 75 (110)-(1×2) we find a preference for unlike nearest neighbours. Pt 25 Rh 75 (100) exhibits after a preparation temperature of 900°C a preference for clustering whereas after a preparation temperature of 600°C, comparable with Pt 25 Rh 75 (111) and (110), ordering tendencies appear. Additional investigations of the chemical identity of atoms surrounding hollow positions show mostly small deviations from a random distribution. However, the number of hollow sites surrounded by Rh atoms only can be significantly affected by the short-range order. Pt 25 Rh 75 (110) exhibits a (1×2) missing-row reconstruction after annealing above 700°C. After the first annealing of the sputtered surface it is accompanied by mesoscopic long-range ‘waves’ with a height of approximately 2 nm and a wavelength up to 200 nm depending on the preparation temperature. |
| Databáze: | OpenAIRE |
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