A study of CH3 islanding on Cu(111) by STM and LEED
Abstract
The formation of close-packed two-dimensional CH3 islands on the Cu(111) surface was directly observed by STM. It was shown that chemisorbed CH3 tend to aggregate into a (√3×√3)-R30^0 structure at any coverage up to one saturation monolayer, consistent with LEED data. Higher resolution STM images revealed ''jagged''-shaped CH3 islands with various sizes and a coexistence of ''liquid-like'' mobile CH3 species and ''solid-like''islands. Upon annealing, an island melting transition occurred with a size-dependent melting temperature around ∼75-100 K. However, LEED patterns showed that a short-range (√3×√3) CH3 order seemed to retain to a much higher temperature ∼400 K. Such a tendency for CH3 aggregation could explain the observed first-order reaction kinetics and simultaneous production of C_2+ alkanes, e.g., from C_2H4 to C_4H_8, at the same temperature. Finally, several types of point defects inside a CH3 island showed distinct bias-dependence contrasts, manifesting a rich structure-dependent electronic response in this simple hydrocarbon adlayer. This work is the first STM observation of island formation with hydrocarbon radicals (CH_3).
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MAR.K1200C