Structural aspects of the fivefold quasicrystalline Al-Cu-Fe surface from STM and dynamical LEED Studies
We investigate the atomic structure of the fivefold surface of an icosahedral Al-Cu-Fe alloy, using scanning tunneling microscopy (STM) imaging and a special dynamical low energy-electron diffraction (LEED) method. STM indicates that the step heights adopt (primarily) two values in the ratio of tau, but the spatial distribution of these two values does not follow a Fibonacci sequence, thus breaking the ideal bulk-like quasicrystalline layer stacking order perpendicular to the surface. The appearance of screw dislocations in the STM images is another indication of imperfect quasicrystallinity. On the other hand, the LEED analysis, which was successfully applied to Al-Pd-Mn in a previous study, is equally successful for Al-Cu-Fe. Similar structural features are found for both materials, in particular for interlayer relaxations and surface terminations. Although there is no structural periodicity, there are clear atomic planes in the bulk of the quasicrystal, some of which can be grouped in recurring patterns. The surface tends to form between these grouped layers in both alloys. For Al-Cu-Fe, the step heights measured by STM are consistent with the thicknesses of the grouped layers favored in LEED. These results suggest that the fivefold Al-Cu-Fe surface exhibits a quasicrystalline layering structure, but with stacking defects.
- Research Organization:
- Ernest Orlando Lawrence Berkeley National Lab., CA (US)
- Sponsoring Organization:
- USDOE Director, Office of Science. Office of Basic Energy Studies. Division of Materials Sciences (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 793778
- Report Number(s):
- LBNL-49714; SUSCAS; R&D Project: 505501; TRN: US200208%%62
- Journal Information:
- Surface Science, Vol. 495, Issue 1-2; Other Information: Journal Publication Date: Dec. 10, 2001; PBD: 15 Apr 2001; ISSN 0039-6028
- Country of Publication:
- United States
- Language:
- English
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