Chemical ordering and reconstruction of Pt25Co75(100): an LEED/STM study
| Autor: | R. Baudoing-Savois, Michael Schmid, P. Dolle, Y. Gauthier, Peter Varga, E. Platzgummer, W. Hebenstreit |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Low-energy electron diffraction
Alloy Resolution (electron density) chemistry.chemical_element Surfaces and Interfaces engineering.material Condensed Matter Physics Surfaces Coatings and Films Crystallography chemistry Phase (matter) Materials Chemistry engineering Platinum Layer (electronics) Cobalt Surface reconstruction |
| Zdroj: | Surface Science. 396:137-155 |
| ISSN: | 0039-6028 |
| DOI: | 10.1016/s0039-6028(97)00665-1 |
| Popis: | The surface of a disordered Pt25Co75(100) alloy has been investigated using quantitative LEED, AES and UHV-STM at room temperature. Atomic-resolution images reveal that it reconstructs with close-packed rows shifted by half the interatomic distance, from hollow to bridge sites. The density of shifted rows increases with the surface Pt concentration, leading to (1 × 5), (1 × 6) and (1 × 7) patterns. Segregation and chemical ordering lead to the formation of c(2 × 2) domains between the shifted rows. Chemical resolution was achieved with STM: the apparent height of the Pt atoms in the STM topographs is about 0.1–0.4 A above that of Co, whereas LEED shows that Pt atoms are geometrically ∼0.04 A higher. The composition was determined down to the fourth layer. An oscillatory segregation profile is observed, with Pt-rich layers (〈C1〉 = 62.6% Pt, 〈C3〉 = 53.5%) and Pt-depleted layers (〈C2〉 = 6.9%, 〈C4〉 = 2.7%). Chemical ordering is present in the third layer and the four-layer surface slab stabilises with a structure and a composition quite similar to that of the L12 PtCo3 phase. As regards the composition and ordering of the top layer, there is a remarkable agreement between chemically resolved STM analysis and LEED analysis. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect