Abstract
Surface structures of self-assembled methylthiolate and ethylthiolate monolayers on Au(111) have been imaged with STM. For saturation coverage of 0.33 ML at room temperature, the well-known (root 3 x root 3)R30 degrees phase routinely observed for longer chain alkanethiolates does not appear under any conditions for adsorbed methylthiolate and ethylthiolate. Instead, both thiolate species organize themselves into a well-ordered 3 x 4 structure. We thus conclude that the stable structure for saturation coverage of methylthiolate/ethylthiolate on Au(111) at RT is 3 x 4, not (root 3 x root 3)R30 degrees as generally believed. For coverage less than 0.33 ML, a striped-phase with short-range order is observed for methylthiolate. Fourier transform of the STM image from the striped-phase produces a clear (root 3 x root 3)R30 degrees "diffraction" pattern. This strongly indicates that the (root 3 x root 3) R30 degrees diffraction pattern for methylthiolate monolayers reported in literature is likely from the striped-phase, rather than from a true (root 3 x root 3)R30 degrees lattice in real space. Consequently, theoretical modeling that reproduces the (root 3 x root 3)R30 degrees structure for methylthiolate monolayers should be re-examined. (C) 2011 Elsevier B.V. All rights reserved.
Original language | English |
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Pages (from-to) | L31-L35 |
Journal | Surface Science |
Volume | 606 |
Issue number | 5-6 |
DOIs | |
Publication status | Published - 1 Mar 2012 |
Keywords
- Alkanethiol
- Surface structure
- Au(111)
- SAMs
- Gold
- Scanning tunneling microscopy
- Self-assembled monolayers
- Adsorbate